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Thread: MODIFICATION , STOCK 2BBL KEIHIN CARBURETOR

  1. #1
    DX User s0crates82's Avatar
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    Exclamation

    NOT SO WILD KEIHIN MODS
    Mechanical Secondary Conversion
    KEIHIN-CARB-INTAKE PICS
    KEIHIN-CARB-INTAKES
    FLIPPING-STOCK-AIR-BOX-LID

    MORE WILD KEIHIN MODS
    VACUUM REMOVAL DIAGRAM
    VACUUM LINE REMOVAL DISCUSSION
    .

    okay fellas, i've got a carb, i've got headers, and i'm getting a cam.
    but.
    on the old board you guys were talking about a mechanical secondary, and i have no idea what that means at all.
    all i know is, that when it was discussed, it was a wow kinda thing, that was a real performance booster, seemingly to be very inexpensive.
    can those that have done it, discuss it in detail... that is, a how-to and the possible benefits reaped from rigging it up?
    thanx

    in theory?
    i thought you said you spun your tires in d2... that's pretty dramatic.
    is it worth doing? does top end suffer as a result of this? are there any drawbacks?
    and hell, how do i do it?

    ok guys, i tried this, but it seems that i was better off without it.
    why? because in doing this you kinda slaughter your idle boost contrller linkage, and believe it or not, this does affect your idle.
    ------well, it did mine.
    i must confess, it felt like the car had a lil more pick-up from a standing start, but it could have been totally psychosomatic.
    dunno, i think if you're gonna do it, power to ya, but try and get that lil metal widget (that actually is kinda yellowish) off a junked car.
    does anybody know how it works? i mean, nothing presses against the widget when you put it on the secondary throttle barrel's throttle shaft... does it bump up against something when accelerating?
    anyhoo, that's my rant.
    Last edited by A20A1; 12-01-2005 at 02:05 AM.
    -Tim
    -------------
    You sold me queer giraffes. I want my money back.



  2. #2
    it's not a real performance booster as much as just allowing the carb to breathe more. In theory it DOES boost performance but the top end is still restricted by the tiny bore carb and cheapo manifold. All it does is use your foot power to open the secondary bore in the carb versus using engine vacuum.

    are you the guy who was emailing me about putting the Prelude arms in your car? if it's you I'll do the conversion for you while you're here
    Last edited by A20A1; 12-01-2005 at 02:06 AM.
    Eric
    3geez member since October 12, 2000
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  3. #3

    A20A1's Avatar
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    It doesn't cost you a penny... but it does take some time.
    I'll dig around and see if i can find the pic.
    Below is a pic of a direct Vacuum secondary which bypasses the vacuum bleed and so it doesn't need to connect to the "T" fitting.
    It was me who posted it... sorry bout the delay... I'm working on it but if you don't have the A/C idle boost linkage on the right side of the carb then you may not be albe to do it.



    MECHANICAL SECONDARY CONVERSION
    WARNING! The mechanical secondary has been known to cause throttle stick which could cause you car to accelerate out of control, this could be due to one or two things:
    1) The throttle nut on the throttle shaft is tightened too much causing the thottle plates and linkages to rub against the carb body.
    2) The part used in the mechanical secondary conversion placing too much pressure between the primary and secondary linages causing the secondary linkage to hold open the primary linkage after the secondary has first begun to open.
    *Please double check the thottle linkages to make sure nothing is binding and that the throttle plates close quickly and freely withtout getting hung up on somehting

    The first visable part after the nut on the secondary throttle shaft is taken from the right side of the carb and was a part of the A/C IDle boost linkage.
    The Hex Nut that is holding everything on the Secondary barrels throttle shaft, has a small washer that will have to be removed... then you can stick the yellow part in it's place.
    Sure you did it right??? make sure you remove the washer before putting the yellow part on... there is very little metal that the yellow part will come in contact with... with the thin washer in place, the secondary won't open... with the washer off, it will.
    oh you have to adjust the rear throttle stop screw if idle is that bad.
    Hmm maybe if you have a manual trans you might not have certain parts on the linkage.
    but I had no problem when I did it... and the yellow part isn't supposed to hit something it actually just locks a part of the secondary linkage so it's now connected to the movement of the primary barrel. As you get closer to WOT the primary opens the secondary but it's not supposed to open the secondary right when you push the gas...
    Yes it is better to get a spare part cause you can still have the A/C idle boost hooked up.
    Oh you can also dissconnect the hose to the vaccum diaphragm that used to pull the secondary open, then plug the ends with vaccum caps.
    The main reason for doing this is that you will gain better throttle response, because you don't have to rely on vaccum.
    the one I drew, not an actual pic.






    ---------
    oh the secondary should have a tapered port. meaning you have to drill the jet so it has a funnel shape going into the main jet hole which will be 1.70mm. but the funnel opening can be larger just don't drill too deep.
    |\_/|
    | || |
    drill it like the image above
    oops its sort of crooked
    well the weber jets are made like that the bigger they get... it helps smooth the flow of the fuel, just like velocity stacks on carbs help smooth the air flow.
    idle is only good till about 2,500 rpm. so I guess it could be why you stall if you stomp the gas... not sure how to increase the idle jet, but turning the screw can only do so much, but it's worth a try.
    anyways it's only a spare carb... so drill the mains and test the carb out... then work on the idle and accel pump jets.
    on the daily driver carb adjust the thigs doug suggested.
    Last edited by A20A1; 01-05-2006 at 05:10 PM.
    - llia


  4. #4

    RCracer's Avatar
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    Question

    Hi
    can someone post a how to on the mechanical secondary on the Honda carb.
    I am going to get a weber (I already have a couple of 38dgas from a Scimitar) I just need the manifold adapter and the linkage brackets.
    Anyway I will be putting a weber on sometime but for now the accord runs ok and just thought that if it isnt that much hastle I would convert it to mechanical secondary as sometimes my car goes really well and others there is a delay in the secondary opening. A mechanical linkage instead of the vacuum operation whould help with that.
    Will the carb settings need changing?
    Thanks
    Paul:smokin:

    I know Ive seen this posted before but I cant remember who posted it and on which board.
    Im sure it wasnt that hard either.

    Hi
    thanks for the pic on how to do the mechanical secondary.
    I have the AC boost thing on my carb (not connected to anything) and was about to take the air box off when (typical UK) it started to rain. I will have a look to see what I can make out from your pic and my carb when I can (when the weather will let me :lol ).
    Thanks
    Paul
    Last edited by A20A1; 12-01-2005 at 02:07 AM.
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    3Geez Veteran ACCORD EX's Avatar
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    just what a i wanted to post ! yeah some one plz explain this !
    MIKE

    i thinks so ! but you 'll have bad gas milage ! just like making the second barell open earlier ( if you do it mechanically !)
    MIKE

    it didn't go much down because you didn't change the time when the second barel opens !
    a friend of mine did it in his old corolla and the second barell was openning really early , so he had shitty gas milage !
    MIKE

    hey Mike ! do you still have the pic of the scondry mechanical conversion ! ?
    MIKE

    yes pleeeeeease !
    MIKE

    me too ! we need a how to on this ! and may be life pictures ! before and after !the before are easy to get but the after , you can get them Alex !
    MIKE

    thanx Alex ! :super:
    MIKE
    Last edited by A20A1; 12-01-2005 at 02:04 AM.
    3geez member since October 4th 2001

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    let me get this start.
    1. take yellow thing off left side
    2. screw on the right side
    thats it?
    sorry i had that backwards. take off right side and put onto left. im not a great mechcanic so i get confused real easy and need things spelled out. im sorry.

    so basically to get at the A/F screw i HAVE to take the carb off? also my float level is real dirty i think cause i look in and see nothing so i just screwed it all the way at as far as it would go and MAJORLY flooded the engine. it was kinda funny looking down the secondary tube and seeing half full of gas. for the 10 seconds the car ran i must have been getting like .1mpg

    lol i know what those part are i just wanted to know if there was a way to get that damn cap out of the A/F screw tunnel without taking the carb off.
    Last edited by A20A1; 12-01-2005 at 02:10 AM.

  7. #7

    hondaman87's Avatar
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    well on my secondary it opens all the way

    what i use was the power of the vaccum w/ a manual switch to turn on and off and i've got a lot of power by doing that

    I'll post pics as soon as i get a scanner

  8. #8

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    OK so, i was sitting one day and watching Junk yard wars, love that show.
    and i got this idea. Secondary fuel jets are bigger, i am assuming. am i right?
    so what i am asking is what kind jets are those on the picture?
    i think they are fuel jets, am i right?
    so anyway with little mod i want to putt secondary jet into primary barrel.
    it will fit i just tried on my spare carb.
    what do you guys think?
    Is it worth it or not?

    oooooooohhhhhhhhh, i see now.
    my friend told me that is where my fuel comes out. i don't know what they supposed to do.
    is there a way to take jets out?

    man i just got a look at them, man you can see the diff in size of the hole they have.
    if i can't take them out, is it possible to drill primary jet.

    are the venturi has diff size jets inside right. i am sure they spray diff.

    well when i did secondary conversion my milege didn't go much down. i think i lost like 3 miles per gallon. but i am still making like 30 miles per gallon. i know that with redriling primary jet, yeah i will lose some milege.
    does anyone know where is Air jets located? A20A1 do oyu know where they are located?

    ok so here is what i am gonna do. because i have another carb on the 88 accord my "bitch mobile" i am gonna drill the fuel jets. the smalles drill i found was 1/16 of the inch 1.6mm. i know it will putt too much gas in it but it is worth trying. plus i am gonna redrill the secondary fuel jet too to a little larger one. may be 5/64 or 3/32. i just drilled the 3/32 in the secondary on my spare carb, it made it a little bigger i am not sure how much diff in performance. i am using this carb for practice.
    on the real carb i am donna drill the primary to 1/16 (1.6mm).
    i am not gonna do anything to airjets, i just want to know where they are. i want to clean them, make sure no dirt or anything in there.
    oh yeah and my secondary thing, i will have to remove that bolt i putt in to open early. when primary opens at full the secondary starting to close, it goes overboard. so i am taking out and i am leaving like Mike told us. yeah it will have to work harder at starts but i think that with new fuel jet sizes it should be fine.
    well it is friday, so it is party time. i will tell you guys how is everything sometimes this weekend or monday for sure.
    Man i love cheap mods.

    why does it have to be funnel type? what is that for?
    should i do the same for primary too, make a funnel.
    thanks.
    mike you are a lifesaver.

    Originally posted by doug
    my opinion is that if you are getting 30 mpg then you have the carb set too lean, or you drive like your grandmother. rather than start drilling out jets and basically blindly f'ing up the dynamics that ENGINEERS developed during design and implemention of the carb, simply try adjusting the float level and maybe the air/fuel idle screw. GOOD LUCK!!!
    I have done all that. my float leavel i high, my carb is running reach. i can smell gas comming out of my exhaust. the way i adjusted mixture screw : i unscrew it till i got the max RPM than i started to srew it back just till it stated to drop the rpm. i stoped right there. my car had never ran so soothe and fast since i bough it.
    so don't tell me i am driving like grandma. i get 30 mpg on highway, and around 25-27 in the city or just driving everywhere.
    i don't drive like grandma, trust me, ask my neighbors.
    i can't help if my carb works awesome.

    ok i hope this picture helps, because this is what Mike told us how to. it worked for me.

    ok guys i will try to post some pictures as soon as possible,

    OK, so i just did it.
    here is what i did. i redrill primary jet to 1.6mm or 1/16" and secondary to 1.9mm or 5/64". plusi took the bolt that was allowed me to open my secondary early.
    well he is what i got, i am missing bang now. it is not because of the jets. they are great, at low rpm i am pulling good, but i am thinking that secondary doesn't open early enough to get enough air into the engine.
    so i am gonna putt this my secondary conversion back together and hopefuly i will get more air into it. i am sure it will be nice after that.
    Overall, it is not hard to do. but is it worth it. i don't think so.
    Oh well at least i tried.

    ok, adjusting throttle cabel did a lot of things. when you stopm on it you can fill push in a seat.
    there is still one problem i am running way way way rich, wich i should be able to fit it by adjusting mixture screw. my exhaust smells like my friends 302 ford with 4 barrel on reach side.
    i don't know my gas milege but i can tell you know that it is not going to be as high as it used to.

    so, i know it is a litttle to rich but it pulls hard now. i don't have anyproblem with under 3000rpm anymore. i just floor it and it goes.
    no more nose dive and take of.

    dude i would like to, but i don't have time to go to the track.
    school is killing me.
    well, i may get this Gtech thing and see if it gonna do anything.
    what is your 1/4 mile time?
    P.S. i am sure i am still in 16-17 sec zone. there is no way to get away from that zone with stock carb.

    and now after a long wait and many requests i would like to show you how to do the conversion.
    first of all look at the picture before.
    this is what your carb looks like right now.

    ok, know you will need to get a part. i would suggest going to junk yard and pull one off or if you have spare carb it will work too.
    you don't have to do anything to it. just take it out.

    damn forgot to post picture
    Last edited by A20A1; 12-01-2005 at 02:08 AM.
    Alex.

  9. #9

    A20A1's Avatar
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    thats not the jets...
    the primary main and secondary main jets are in the float bowl.

    Well it's not because the second barrel is opening at the wrong time... it because the second barrel was previously controled by high vacuum, so if you didn't press the gas hard then the secondary wouldn't open as fast... but since it's now mechanical the opening time is set.
    You don't want to drill the air jets... there is also external ports that I think lead to the air jets but you can plug at least one of them off... the ports are on the carb top hat and are connected to A, B, or C from the air jet controller.
    Drilling the primary jets will be hard cause you need to keep the drill straight and even then you could be increasing the jet size too much... jets sizes increase by 0.05(milimeters I think), and the difference is pretty dramatic for such a small increase.
    The best thing would be, drilling the jet out and screwing in a jet from a weber 32/36... not sure if it could fit but it's worth a try if you have a spare carb
    and don't mess with the venturi's and don't rejet the spray nozzle.. spray jets only leak gas into the cylinder when the pressure in the venturi is less the the pressure in the float bowl.
    you could raise the float level a tiny bit... and that will effect just about everything on the carb. but be careful since the float adjustment screw is notorious for leaking.

    just don't over do the float level... normally if you need to raise the float level a lot then it's probrably time for a bigger fuel pump.
    but i doubt thats the case in your car.

    1.9 is big... I used 1.9 cause in the secondary cause I was reving high and it was still really rich on the air fuel guage...

    plus you drilled the main jets bigger but din't increase the air correction jets... mine worked good as a 1.60/1.65 or a 1.65/1.65

    not sure what the air correction jet is... since the 2 jets above the mains could be emulsion tubes.

    come on then posat some 1/4 mile times... no shame.

    yes you have to remove the airbox... the peice is off the drivers side of the carb below the fuel line.
    You put the peice on the left side after removing the washer from the second barrels throttle shaft.
    the second barrel throttle shaft is the one closer to the valve cover... you sitck the piece on the second throttle shaft.
    if you get and old carb and you can retain some functions of the a/c idle boost... if not your car may shake when you turn on the headlights and the a/c

    it's a gain in throttle response... I doubt it will add hp... it may give more hp down low.. you still need to make up for 1mm of play in the primary linkage where it contacts the secondary linkage... kinda hard to decribe....

    hmm well the primary is the lower end so try and redrill that one... start with the smallest... if you can try to find out what size the jets are stock.

    yeah it will have better acceleration.... I was struck with that too... I jeted the weber rich to get better off the line times but overalll acceleration dropped... the power seemed flat in the mid range.

    I've got a 1/32" you just have to look for the sets with tiny bits in them... search the hardware stores, its the only place I found mine... other than Wal-mart maybe.
    oh a hobby store too...

    yup they leak 80% of the time on old carbs.
    if you want to replace the o-ring you'll have to remove the top portion of the carb and screw the float screw all the way in to remove it.
    the float window is a thick piece of glass held in by twop screws and a metal plate with the metering marks.

    ooop's sorry dude...

    Yeah you could look at it that way... but the amount exhaust you can move out of the cylinders determins how much air fuel mix will try to enter the cylinders. So even though more air and fuel could go in doesn't mean it will. I'll still have to modify the valve train and head for better flow. Rejetting then would be nessesary, but as it stands now, the basic jetting for the weber is still a work in progress... and I went out of step when I got the cam first before finding the baseline jets.
    Last edited by A20A1; 12-01-2005 at 02:09 AM.
    - llia


  10. #10
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    those are the venturi bodies

    my opinion is that if you are getting 30 mpg then you have the carb set too lean, or you drive like your grandmother. rather than start drilling out jets and basically blindly f'ing up the dynamics that ENGINEERS developed during design and implemention of the carb, simply try adjusting the float level and maybe the air/fuel idle screw. GOOD LUCK!!!

    it's your spare carb to trash if you please. let me suggest that before you do the dentist trip on it you completely clean it and then set the level either at or slightly above the highest mark on the glass. Open the air fuel screw a half turn to begin. Make real sure that your accelerator pump diaphragm is solid and that the passage ways are clear and you are getting a good solid squirt of fuel. Check the power valve, rod, and vacumm to that port. Also check that the vacuum lines concerning the secondary are open and functional, if you have mechanical secondary setup then you most likely will have a "point" in acceleration that is kinda flat.
    Last edited by A20A1; 12-01-2005 at 02:10 AM.

  11. #11
    SEi User Mantis88LX's Avatar
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    I cant find any post that describes how exactly to do this, whats the easy way to do this and what exactly is it that it does, and how much power increase is expected

    i still dont really understand

    lol mine already shakes with the headlights on, ?? dont know what thats all about, im interested in this secondary conversion, how much hp u think is gained?
    Last edited by A20A1; 12-01-2005 at 02:11 AM.

  12. #12
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    what side of hte carb is the piece on, and where is it below the airbox?
    Slow as fuck, need to make it quick

  13. #13

    shepherd79's Avatar
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    after you got the part from a junk yard carb or spare carb( make sure the original still there) you will have to putt it on.
    unscrew the nut and take the washer out. slide the part on and screw the nut back on. DO NOT putt the washer back on, the nut will not fit with washer.
    after you done that. go to the other side of the carb and disconect the vacuum from secondary. if you leave the rod there it will get stick so what i did on mine is bended 1/2 inch.
    ok so this is what you should have when you done with it.

    after you did that, you will notice that your car has this fuel starvation problem, no problem.
    first, adjust the float level almost to the top bar in the float window.
    second, adjust the mixture screw. unscrew it all the way out, your RPM should go up. after that start screwing it back in. as soon you will hear rpm drop stop there. you should be set for now.
    well i hope it helps. if you have questions just PM me or send AIM, or email.

    well, i just took the car for a run, and i can tell the diff with the stock carb.
    on the redrilled one, my car would get nice smoth run from 2000 till 6000 rpm with no hesitation what so ever.
    i am switching back to redrilled one.
    i may redrill this one with smaller size. the one i did has 1.6mm primary and the second one 1.9mm.
    what size do you think i should do this one?
    i am thinking may be like 1.2mm or 1.4mm primary and 1.6 secondary.
    what do you think?

    well, the problem i can't find drills smaller than 1/16"
    where can i find them?
    oh yeah, another thing. i have notised that with stock jets my car has a lot faster acceleration. can it be that with redrilled ones i was putting to much fuel into the engine?

    ohh you may want to take the window out and clean it. and be carefull with float level screw, it can leak.

    no you can't take it of without removing the carb.

    cool,
    thanks,
    how did you come up with those numbers.
    i will try this numbers. i think i am gonna have to order the 1.15mm drill. i just can't find this small in the stores.

    well, hold on a sec.
    i did mine 1.6 for primary and 1.9 for secondary.
    you are right when i did the primary i took out a lot of metal, but when i did the secondary i took out just a little of coper.
    so here is what i am thinking,
    1.2mm for primary and 1.9 for secondary. i think primary is more like 1mm. so if i do 1.2mm it should do nice.
    and for the secondary, 1.6mm drill bit is too small so i am guessing 1.9mm should do nice.
    all i know is that 1.6 and 1.9 setup is nice when you hit high RPM, but when you get to low band it suck ass. i think it is because primary it too big and it is getting too much fuel.
    anyway, i just got 0.8mm and 1.2mm drill bits. SOB cost me like $12. they come in pack of 4 each size.
    if you find Dremel section , you should find small drill bits.

    mike post the pictures of what are you talking please.
    i would love to push more fuel into my keihin carb.

    where is the picture MIKE?

    and that is why we want to switch to weber or holley carb.

    what did you do?
    show us some pictures.
    i want to see how bad you messed up.
    Last edited by A20A1; 12-01-2005 at 02:12 AM.
    Alex.

  14. #14
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    When you modify (open up) exshaust then carb must also be re-jetted to make it run better.

  15. #15

    A20A1's Avatar
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    man you were on this late... jeez it's like 2 right now... I'm phazin in and out though... I'm gonna go look for drill bits tomorrow too.
    EDIT: actually make that today... afterI get some rest.

    hmm it looks like I was wrong:
    The stock jet sizes are like
    1.20 Primary
    1.80 Secondary
    I tried the 1/16 drill bit on the primary just a tad (hand turned).. and you can see a ring of exposed copper just slightly larger then the stock jet. about 0.10mm - 0.20mm larger.
    Same goes for when I tried the 2.40mm bit on the secondary... by the size of the ring I'd have to say the bit was .10mm - .20mm larger. and the 1.60 was 0.10mm - 0.20mm too small. average them out and you get 2.0mm stock secondary jet size.
    in either case 1.60 for primary is too big
    and 2.40 for secodnary is too big.
    well that was $12 for that lesson...

    I hand drilled the accel jet... not all the way through... I increased the diameter in steps and left the exit port of the jet the stock size.... hopefully this will let a little more gas in and force the spray to be wider, thus finer and easier to burn.
    I also drilled the main jets in steps... again not going all the way.
    both main jets now have a 2.4mm opening and the primary has the middle 1.6mm but at the exit it's still the stock size.

    Well leave it to keihin to provide the linkage to easily convert the carb from a vacuum secondary to mechanical...
    And guess what... they also made it possible to have a secondary acceleration jet. It will take some precision drilling and micro line for the fuel. but the bulk of the materials are readily available off the carb.
    one other thing. the push rod for the accel diaphragm will have to be longer... a tougher spring will need to be used and can be found off the carb parts as well as a larger diaphragm. then you need to increase the length of the linkage that controls the rod that is connected to the pump arm.
    increasing the length will increase the travel of the pump arm on the other end, thus more fuel will be squirted out to make up for the use of the second jet.

    haha
    sounds good, I won't be able to get it just yet though.

    well I will really have to do a few drives with and without it.
    I tired to drive with a direct loop and things got funky, but it could have been cause my car was cold.
    then I tried a checked-loop
    I added a check valve so that vaccum it pulling from the primary from both ports, but the secondary only uses 1.
    it seems better... I really with i had the secodary accel pump diaphragm hooked up.
    vacuum check valve it the white orage vlave in-line with the vacuum lines. the arrow or direcrion of air flow is from the white end to the orange end.

    the carb hates it when the secondary draws vacuum on the primary.
    EX: Vacuum line hooked from the venturi port with taps to both barrels to the venturi port tapped only to the primary. Check valve is in-line, with vacuum drawing from primary to secondary.
    I'm sure I could get something positive to happen... I just need to figure out which port is causing the problems. Should I block a tap or should I enlarge a tap. should I run vacuum from the intake above the carb to a venturi tap...
    basicly I want to make an enrichment circuit so the hesitation of opening the secondary from and dead stop will go away, without going throught the hasstle of redrilling jets. I'll get into more detail later.

    "Opening the secondaries mechanically causes the same fuel delivery gap in the secondaries as the primaries, making an accelerator pump needed. It is possible in some cases to have a long duration primary pump shot that covers the secondary opening, but individual runner set ups will always need a secondary accelerator pump."

    Hmm I ould increase the duration if only I had a good drill press and a way to add on extra aluminum to a small casted or milled part.
    other wise i'll have to go for the seperate accel jet diaphragm.
    I've made a small one but I think I F()K#D up and the diaphragm may leak.

    K you guys... I'm working on upgrading the keihin to work and work well with the mechanical secondary.
    I'm adding in weber Air correction jets ( I drilled large holes above the emulsion tubes in order to accomodate the jets)
    I'm redrilling the main jets.
    I'm possibly increasing the idle jet and accelerator pump volume.
    right now i have shaved the top hat flat.
    this means everything but the float adjustment screw is gone. Yes the float bowl vent tubes above the barrels are gone... so is the power valve (something I will have to add in later or not at all, and just lock the valve open)
    The tricky part is knowing if i should plug the air jets internally... there are a few ports on the main body of the carb that have me worried that if i were to plug them internallly I'd also be pluggiong someting else. I'll let you know once I've tested everyting.

    Something interesting I notticed... the primary Air correction jet is around 160- 175 when the air jet controller is in use... and there is a difference between the 86-87 air correction jet and the 88-89 air correction jet... one has a 60 and the other uses a 65. the higer the # the leaner the fuel mixture... well the greater the braking force on the gas in the emulsion tubes. Which means if I use a + 25 + 30 ruel for the mains.
    The primary main jet should be around 135 - 150
    More then likely its 135 but I no longer have a way to tell and I forgot all my old measurements of the jets.
    Anywho... thats why plugging the air controll jet does wonders... cause it keeps the Letter A which is the 100 air correction jet
    and letter B which is the 110 air correction jet from being used.
    So weighing a 65 jet against even a 135 main which is fairly small... would create such a low braking power that you'll come out with a richer mixture.
    BTW letter C is the 60/65 air controll jet.
    connecting B to C whould give you 170 - 175 air correction
    and
    connecting A to C would give you a 160 -165 air correction
    This may be good later on when doing emissions testing
    anyways back to my project... i thhink I'm gonna bust out another top hat from the junk yard... seems I have another plan and some of the drilling I did went a little too far. it looks real nice but I think in the lkong run starting over again will save me some greif of getting the carb to work right.


    Here we go...
    The Majority of the top hat was filed flush except for the float adjustment screw. The the Power valve, Pri. Air correction, and Sec. Air correction, were drilled out right above the valve and the emulsion tubes. I knokced out a small portion of the wall surrounding the Pri. Air Correction so it could feed into the Float Bowl. New Jets will later be glued directly on top of the emulsion tubes.
    Then I added metal putty and formed and filed a smooth transition into the barrels also removing some restrictions.
    I blocked off the first rear vacuum port with some putty and the third vacuum port (power valve) as well.
    The remaining port in the center of the two was left to be connected to venturi vacuum port on the carb body near the accelerator pump diaphragm.
    Under the top hat, the bleed canal for the accelerator pump has been blocked off. Also the hole that used to contain the 60 or 65 air correction jet had been blocked off with putty.
    ...
    ...
    .

    I've rerouted the vent for the primary... now the venturi vacuum sucks up the gasses from the area above the primary emulsion tube and the float bowl.
    The secondary vent should still work, it's actually open abit more then it was stock, exposing both the secondary air correction jet and the float bowl.

    Here is the new venting layout...
    oh and the rear vacuum port needs to be cut a bit shorter cause there is a vacuum restrictor glued into the port, which will get in the way.
    Last edited by A20A1; 12-01-2005 at 02:13 AM.
    - llia


  16. #16


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    Hey man, I have the Keihin carb that came off my car when I installed the DCOEs. It's a bit roughed up - LOL, but it's yours if you wanna pay shipping. I think the experimenting you do with the Keihin carbs is important. Email me if you're interested. I got some others stuff too, that I'll throw in the box.
    "Hey, it looks like he just opened a box and cleaned out his garage. Is that an empty coolant bottle and a bag of garbage?!"
    :lol

    No sweat. Just lemme know when ya want it. It's not going anywhere.

    I would just like to say that you guys who are modifying the Keihin carburetor are amazing. I've been reading through this post and I am totally impressed! You should all team up, work together (by using email and shipping the carbs to each other) and sell modified carbs on the forum. You could sell a "modified carb and intake kit" and people would buy it up - especially if you could approach the power of the fuel-injected models. Just a thought
    I'm bored, lol.
    Last edited by A20A1; 12-01-2005 at 02:13 AM.
    Mike Clark

  17. #17
    LX User mindlos's Avatar
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    You never cease to amaze me.

  18. #18
    LXi User
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    any possibility of creating a flow problem by blocking off the vent tube? I'm wondering if the lack of breathing for the float camber will create somewhat of a restriction to the fuel flow.

  19. #19

    A20A1's Avatar
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    carb

    top of top hat

    rejetting the keihin (Air correction jets)
    I only had a 160... so I used that to show you what it would look like... but I plan to use smaller air correction jets... or increase the main to match the higher air correction. in any case here is the pic.

    close up

    bottom of top hat
    Last edited by A20A1; 12-01-2005 at 02:14 AM.
    - llia


  20. #20
    damn man that's crazy :lol
    I did some shit not even half as bad and killed the carb, I threw away 2 of them ad said fuq this I'm getting a Weber
    let me know how that runs
    Eric
    3geez member since October 12, 2000
    "All this worldly wisdom was once the unamiable heresy of some wise man." - Henry David Thoreau

  21. #21

    A20A1's Avatar
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    bump I added more info to this post.

    k here is how I tapered my main jets.

    Okay... I still want to test out the Keihin... so I decided to reapply the float... I had no luck in hammering out the float pin, so I decided to melt half of the floats plastic shaft on the stock top hats so I could pull the float free and then re-welded the shaft on my carb top hat. I also added in the float retainer so I could install the top hat without the float needle dropping out.
    I still need a gasket kit... I hope my float valve doesn't leak.
    Other then that I have no more umm weber jets to apply to the keihin so I may use the keihins ones
    The powervalve will remain open, and I will try it closed as well.
    Other then that this is really a tesat for the porting job... though the amount of work done of the jets kinda ruins the whole experiment. Considering parts of this modified carb were on the car that got the accel pedal stuck and nearly killed me, I'm a bit weary to install it on my baby. But I want to sell my weber so I can work on getting other carb to work.

    Okay bubbies... I just bought a new file set... and had a little bit of sand paper left so i got to work on modifying the booster venturies... I'm cutting down the metal on the support rods that extend out from the sides of the barrels... I believe this will get a little more flow... I'm going to get a camera soon I hope so I'll have pics up shortly... hey shep... how good did having the secondary booster in the primary barrel work out for you? it's kinda off centered and I don't see being able to center it easily.

    Damn, well today i found out something new about the booster venturies...
    The primary booster feeds fuel thru the center of a solid brass bleeding tube and the brass rod sticking into the hole for added resistance or fuel breakup?
    The secondary booster has a brass tube with holes drilled into the walls and the fuel flows on the outside and enters the tube thru the holes instead of thru the center of the tube which is blocled by a brass bit.
    This is very strange... I feel the need to get rid of the metal rod on the primary booster... but shaving down the booster venturi bodies on the bleed tube side could collaps the fuel passage so I wont do that on my next set... I will shave the other side of the booster body though. as for swapping a primary booster into the secondary barrel, I dunno... the sizes are very simmilar and the only modification needed is trimming the flat bit that rises above the surface of the carb body.

    YOu can outperform a 32/36... I'm sure of it... only problem is the smaller float maybe?
    but with the right jetting and opening up the restrictions above the barrels I'm sure it will, the bore on the throttle plate for the keihin is larger.
    Last edited by A20A1; 12-01-2005 at 02:15 AM.
    - llia


  22. #22
    Keihin mods

    1. JETTING - Jets are kind of a bitch on this carb I'm going to try putting in the weber jets as Mike mentiones and I'll let you all know if they fit. I've tried drilling them but it was hard because scraps of metal were clogging up the jet passages making them act SMALLER. If Weber jets can be retrofitted that would be a great improvement, however you still have to get over the fact that jet removal on this carb is one of the more challanging repairs.

    2. Air Correction - You can plug the "C" line going to the front of the carb, just put a vacuum plug nipple on it and you get better mid-to-upper RPM responce. For those not so daring you can always loosen the adjustment acrew on the black device with the "A"/"B"/"C" lines going to it.

    3. Secondary operation - Mechanical secondary has to be one of the best discoveries yet, more power, cool sound... Mike you are a badass. The mod, when installed correctly, is amazingly accurate, it even acts like a progressive linkage.It would be much more effective if you can alter the accelerator pump jetting to match the extra air, most of the complaints about this mod is the hesitation caused when you stomp on the gas. Restricting the air correction (as mentioned above) along with richening the idle mixture helps to an extent, but If you can't deal with it then just connect the opener with it's own independant line to the carb. In stock form this line "T"s off to another line (I believe it was 17??) and to the carb. Just take out the "T", plug the extra line, and connect the opener diaphragm vacuum directly to carb. This will give you a quicker than stock opening without the hesitation from having too small an accelerator pump.

    EGR - Who needs it? Cars with shitty-designed heads and poor emmissions. EGR basically feeds exhaust back into the intake to lower emmissions (the car breathes its own farts) and as an added bonus automakers claim lowered NOx emmissions and increased engine life but this is only due to the fact that the less potent explosion is cooler and if your car has a bad cooling or oiling system it will not be stained as much and last longer. There could be other benefits but I haven't run it in about 3 years. You can plug the hose going to the opener and this will seal the manifold, if you want to go further you cvan remove the pipe going to the header but you will have to plug the hole up on the header or get aftermarket ones with no hole.

    Air suction - who needs it? More emmissions cheating devices. Unlike the EGR, it does little to actually change the combustion process, it merely adds fresh air into the exhaust system and screws up the scavanging effects when it is in operation. Basically all it is - a valve to let air into the pipe. In between the firing of every cylinder there is a small pulse in between the exhaust gases which is low pressure. Every time there is one of these low pressure pulses a reed valve opens and lets each of the pulses draw air into the pipe so it seems cleaner at the other end. This only runs at lower RPMS (less than 2500 I believe) and although having it or removing it makes a minimal change performance-wise, if the system is in disrepair it causes major vacuum leaks and it is an all-around pain in the ass to work with (Have you ever tried cylinder head woirk with this contraption still stuck to the exhaust??? Or putting the pipe back in??? )
    Best move is to saw it off, plug the header, and plug the major vacuum feeds. It frees up lots of space and makes things easier to diagnose, no adverse effects on performance, you will, however, flunk your visual inspection at the smog station (and it won't sound cool when it opens up either, that deep growl produced by the chamber )

    Air Filter - Yes cold air helps tremendously #1 if your carb is tuned right and #2 if the CAI provides enough flow. The stock setup really is a CAI but it is restricted by the narrow pickup at the fender. You have 3 options:
    a) K&N filter to help loosen up restriction
    b) flip the air cleaner lid - more airflow = more power, although if it gets hot enough the gains are cancelled out b/c the carb is pulling in hot air from the top of the engine bay (remember, heat rises). Great winter mod, reversible if you get tired of it, sounds great when you gun the car.
    c) full custom CAI - great mod but can be difficult depending on how much is under your hood. Those of you who have moved batts to the truynk or done other hacking mods removing things have more flexibility. The best setup I had was sucking in air from inside the firewall (where the wipers hide)

    Manifold heat - removing hte heater hoses from the carb will free up some midrange to upper RPM power but can cause drivability problems especially in the morning. Not recommended if temps drop below 40*F where you live. I have the best of both worldsw with a 90* handled valve inline with the manifold. Your temp sensro will also stop functioning if you do this mod, I moved mine to the thermostat housing and quick-steeled the sensor into place of the black vacuum thermovalve. You can probably just swap on an LXi thermostat and use that sensor.

    OIKeihin mods

    1. JETTING - Jets are kind of a bitch on this carb I'm going to try putting in the weber jets as Mike mentiones and I'll let you all know if they fit. I've tried drilling them but it was hard because scraps of metal were clogging up the jet passages making them act SMALLER. If Weber jets can be retrofitted that would be a great improvement, however you still have to get over the fact that jet removal on this carb is one of the more challanging repairs.

    2. Air Correction - You can plug the "C" line going to the front of the carb, just put a vacuum plug nipple on it and you get better mid-to-upper RPM responce. For those not so daring you can always loosen the adjustment acrew on the black device with the "A"/"B"/"C" lines going to it.

    3. Secondary operation - Mechanical secondary has to be one of the best discoveries yet, more power, cool sound... Mike you are a badass. The mod, when installed correctly, is amazingly accurate, it even acts like a progressive linkage.It would be much more effective if you can alter the accelerator pump jetting to match the extra air, most of the complaints about this mod is the hesitation caused when you stomp on the gas. Restricting the air correction (as mentioned above) along with richening the idle mixture helps to an extent, but If you can't deal with it then just connect the opener with it's own independant line to the carb. In stock form this line "T"s off to another line (I believe it was 17??) and to the carb. Just take out the "T", plug the extra line, and connect the opener diaphragm vacuum directly to carb. This will give you a quicker than stock opening without the hesitation from having too small an accelerator pump.

    EGR - Who needs it? Cars with shitty-designed heads and poor emmissions. EGR basically feeds exhaust back into the intake to lower emmissions (the car breathes its own farts) and as an added bonus automakers claim lowered NOx emmissions and increased engine life but this is only due to the fact that the less potent explosion is cooler and if your car has a bad cooling or oiling system it will not be stained as much and last longer. There could be other benefits but I haven't run it in about 3 years. You can plug the hose going to the opener and this will seal the manifold, if you want to go further you cvan remove the pipe going to the header but you will have to plug the hole up on the header or get aftermarket ones with no hole.

    Air suction - who needs it? More emmissions cheating devices. Unlike the EGR, it does little to actually change the combustion process, it merely adds fresh air into the exhaust system and screws up the scavanging effects when it is in operation. Basically all it is - a valve to let air into the pipe. In between the firing of every cylinder there is a small pulse in between the exhaust gases which is low pressure. Every time there is one of these low pressure pulses a reed valve opens and lets each of the pulses draw air into the pipe so it seems cleaner at the other end. This only runs at lower RPMS (less than 2500 I believe) and although having it or removing it makes a minimal change performance-wise, if the system is in disrepair it causes major vacuum leaks and it is an all-around pain in the ass to work with (Have you ever tried cylinder head woirk with this contraption still stuck to the exhaust??? Or putting the pipe back in??? )
    Best move is to saw it off, plug the header, and plug the major vacuum feeds. It frees up lots of space and makes things easier to diagnose, no adverse effects on performance, you will, however, flunk your visual inspection at the smog station (and it won't sound cool when it opens up either, that deep growl produced by the chamber )

    Air Filter - Yes cold air helps tremendously #1 if your carb is tuned right and #2 if the CAI provides enough flow. The stock setup really is a CAI but it is restricted by the narrow pickup at the fender. You have 3 options:
    a) K&N filter to help loosen up restriction
    b) flip the air cleaner lid - more airflow = more power, although if it gets hot enough the gains are cancelled out b/c the carb is pulling in hot air from the top of the engine bay (remember, heat rises). Great winter mod, reversible if you get tired of it, sounds great when you gun the car.
    c) full custom CAI - great mod but can be difficult depending on how much is under your hood. Those of you who have moved batts to the truynk or done other hacking mods removing things have more flexibility. The best setup I had was sucking in air from inside the firewall (where the wipers hide)

    I'll post more as I remember them. I got tired of the Keihin and Mike hooked it up with a Weber.
    Eric
    3geez member since October 12, 2000
    "All this worldly wisdom was once the unamiable heresy of some wise man." - Henry David Thoreau

  23. #23
    LX User
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    Nice Job!
    Last edited by Pro_Mod_Accord; 10-18-2005 at 11:03 AM.

  24. #24
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    im just curious a20a1 did you ever get rid of the brass tube for the primary venturi or what have you done with the kehein lately? it would be real good if you could hit a sweet spot on all the kehein mods maybe even get one to outperform a weber..... nah. id like to know if anything has panned out with this ive done all the basic mods vac removal' manual secondary' a lot of wieght reduction.but ide like to see the carb perform a little better,geuss ill be needing that exaust sooner then i thought.
    "i dont have friends anymore and my favorite hangout is the junkyard but damn it runs good"..... by me. "i know i have not gotten laid in a while but trust me the blisters on my hands are from working on my car"...........by me.

  25. #25

    A20A1's Avatar
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    On the top hat, the area above and below the #14 INTERNAL VACUUM LINE should not be shaved down like I have in my other pics of the top hat... also the vent tube may need to stay in place... the secodnary vent tube can go...



    Only if you are using the weber air control and main jets should you plug any jets on the carb.
    if you use weber air correection jets you need to file down the threads on the jets and the top of the jet to remove the slotted area that is used to unscrew the jet with a flat head.(do the jets one at a time to avoid confusing the jet size)
    You need to make room for the air jet in the top hat... but you should first solder the jet to the emulsion tube beofre hollowing out a space for it to breath in the top hat above the jet.

    the primary air jet can vent to the float bowl... so open up a wall that will only bleed that one jet to the float chamber... and not affect any other jets or internal passages.

    the secondary air jet is easier cause there really isn't anything around it to bother you... so just drill a nice round space for the air jet to have breathing room when you put the top hat over it.


    for the main jets... first widen the stock mains bigger then the weber jets, then solder the weber jets over the mains.

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