Hazwan's Quad Bike Carbs Build Thread

[Hazwan]

Thought this deserved its own thread here so here goes. 2ndGenGuy offered me his old setup if I pay shipping for them all the way from the US to Malaysia so I said YES. I was planning on doing EFI conversion and I already paid CAH for the parts but I guess that should wait for a bit.

My single carb has been running okay although its pretty shitty with the fuel economy. I guess it has something to do with it being jetted slightly rich with all the emission crap and I had the carb devacced. 23mpg city and 30mpg highway is shit IMO. Highway is okay but it could do better and I don't even drive that fast

Weeks later, here they are


Pretty intake manifold


They are Mikuni BST38SS, 38mm in size which is plenty huge for a fairly stock motor I'm running


Long ass runners!




Torn apart for cleaning


Kinda dirty since its been sitting for a few years. All the USDM dust!!




Nasty


Bought a bunch of o-rings to replace most of the perished ones from a local hardware store


Can't replace the hardened up float bowl o-rings yet

[Hazwan]

Main and pilot jets


Drilled them to 1.3mm and 0.3mm initially from stock 115 (I assume 1.15mm and whatever the stock pilot jet size was since its too small and my smallest drill bit only goes down to 0.3mm)

2ndGenGuy had it started and running on his B20A with the stock jets so I assume it won't be too far off with my engine being smaller so I figured 1.3mm and 0.3 should be a good starting point.

Drilled main vs stock


Old carb


Tried to get the manifold off and this hits the dog bone bracket grrr


Its off!!








My solution for the intake mounted coolant temperature sensor


Get an adapter and make it fit into one of the thermovalve holes

[Hazwan]

Installed!





First start vid!



Had to turn if off as it idled too high. Turned the idle screw a little and then heres a second attempt:



It runs!!
https://youtu.be/Kndl7SU2ReU

It starts and runs fine although it sounded and smells lean and I was right


Then I noticed 2 of the float bowls were leaking. Turned out the o-rings are torn (N) so I made my own gasket from a piece of gasket paper


Used the sync vacuum port for my dizzy advance and brake booster. It works!!


Taken apart, again to redrill the jets once again

[Hazwan]

Off again to do some tweaks with the needles and other stuff






Final(ish) setup with vacuum taps on the manifold tee'd together and into the dizzy adance and brake booster


Vacuum is nice at 20-21" during idle


More driving vids!!




I didn't push it hard enough as I need my..... narrowband to at least give me an idea whats going on. Yes I could use a wideband but $$$ is tight Unless someone is kind enough to offer me one too LOL

So far it drives fine. Pulls strong, no hesistation or bogs or anything. Power is smooth all the way to the redline but like I said I need to know whats going on with the mixture before I can tune it further. Right now its all a guesswork and I'm not too comfortable with that.

Last jet size was 1.5 mains and 0.45 pilot with the screws being 1 and 1/2 turns out. Plug reading looks good but I need a long stretch of road before I can tune my WOT and midrange. Safe enough to drive now I guess

[Dr_Snooz]

My God! What is this a museum piece?? You need to drive this car so it gets dirty, foo.

JK. It's always a pleasure to watch you work Haz. When you gonna come stateside and do my car up for me?

[AccordB20A]

haha!! hes should travel the world painting cars

[Hazwan]

You guys should pay for my tickets and I'll travel all over the world and paint your cars

And hey I did drive the car and the car and engine bay do get dirty but I just tend to wash my car every week and wash the bay like once a month so it stays spotless (Y)

Anyway I did more tuning today with my narrowband nose o2 sensor - yes I tune by smell and feel and its fairly accurate if you know what are you doing. I found out that I'm too rich on the midrange around 2-4k rpm. I previously raised the needle using a shim so I lowered it by taking out my shims between the clip and the base since the needles aren't adjustable stock (gay!!) That seems to get the black smoke around 2-4k gone but exhaust still gurgles a bit and engine just doesn't seem so smooth around that rev range.

Took the stock washer off and it seems better-ish. Gonna play with my float heights tomorrow and see whats up. I'm pretty sure my full throttle settings are good but my nose o2 sensor can be fairly inaccurate

Bonus video:



It's so rev happy now that it gets into the redline so easily. Might need to build myself a rev limiter someday.

Its so quick and its not even fully tuned yet!!

[gp02a0083]

i stopped offering to paint other people's cars a while back, no one wants to pay even to cover the material cost. I switched over to pin striping and even so people want the work done , but dont want to pay for awesome workmanship.

[carotman]

Looks awesome!

[87roach]

Sounds beastly man!

Awesome work on getting it up and running so quick, props to John for the deal too

[Dr_Snooz]

yes I tune by smell and feel and its fairly accurate if you know what are you doing.

Yes! I keep trying to convince people about this, but it's hard.

[Hazwan]

Yeah most people can't be bothered with carbs anymore.

So I've got the tune 90% correct. Or so I hope. I've got my narrowband o2 installed and it reads 0.5-0.6v during idle and goes 0.9v when driving and somewhere around 0.7v when I'm cruising. Kinda rich but then it smells and feels right so it must be okay But my plugs look fine so I'd trust my plugs reading more than the horribly inaccurate narrowband. Tuning by feel, smell, plug readings and aided by a narrowband o2 is good enough for me.

Exhaust pops a little but that can be contributed by some holes by the flex pipe.

All that left now is wait for my IR thermometer to get here then I can balance the carbs properly or at least close then I'll build a carb balancer and see if it would get rid of the irregular idle. I'm sure my redrilled jets aren't that accurate anyway!

I need to wait for my air filters then I'll get a set of new plugs and see whats up. Then I might go and test it out at this hill and see if the plugs reading are correct OR if I blew the engine or something LOL

Then I'll take it for a highway/high speed drive and see whats up!

I can't drive the car much until I get my filters for obvious reasons. And the fuel spraying from the carb mouths under WOT is just asking for trouble

[Hazwan]

Ignore the wire mess


Check out my sick AFR gauge

[gp02a0083]

I think we have seen far worse rats nests when it comes to wires! Nice job

[2oodoor]

Awesome project Hazwan!

[Hazwan]

Overnight parts from.. Indonesia


Can't be bothered to find these locally so upon searching the interweb, I found these for $40ish shipped from Indonesia which is the cheapest I could find. They are float bowl gaskets btw. Remember how mine were leaking? At about $10 a piece, it's expensive for what it is!

I wonder why it's leaking


How it looked like yesterday after if poured gas out of the overflow tube. No idea why it did that. Must be dirt or some crap stuck on the float needle as it went away after I tapped the float bowls.


Still waiting for my air filters before I can finalize with the tune. It runs good now, just need balancing and fine tuning but I'll wait till I put the filters on as its gonna mess with my tune right now

[gp02a0083]

man i always like getting Zuki genuine products

[AccordB20A]

awesome stuff

[Hazwan]

Filters were here last week and I've spent countless amount of time figuring out why it's acting like it's lean on WOT near the redline


Searching around and I found mixed opinion about pod filters and CV carbs not liking them and how they would never run right with them. Except why would mine be running fine without them and starts leaning out and spitting through the carbs near redline with the filters on???





Took the filters off and it can get up to 6k just fine but then I noticed that it doesn't really run as good. I didn't realize this before maybe I never actually pushed it hard enough before hmm. But I did reinstalled the stock fuel filter in the engine bay, and perhaps it was restricting the fuel flow a little bit.

To make things even worse I never actually replaced them before I might check them out and see what's up and if that didn't do the trick then the factory pump must be having a hard time keeping up to fill all 4 carbs with all the mad powar I'm making now!!

My plugs look good though. #4 on the far right is a bit lean but I blame my vacuum taps. I'll get that sorted out too. Can't run on WOT long enough to see what's the WOT mixture looks like

[Hazwan]

I finally got it all figured out now!!

Here's a rather long story about it:

Last mains size were 1.5mm and it acts like its running out of breath, like its too lean after 5000rpm with the filters on. Took the filters off and it could rev up to 6k but still acts like its running too lean.

So I enlarged the mains to 1.6mm and it didn't make any difference?! Went to 1.7mm and eventually 1.9mm and its getting worse?!?! It won't rev past 5k even with the filters off and yes its running lean I can tell by the sound and feel.

Did some research and apparently some car engine/bike carbs combo need its main air correction jets to be blocked else you won't be able to get it running right on WOT near redline as it gets too lean. It has something to do with the stock bike setup having its air box and how everything is balanced and designed to work together and since I don't have the box AND the original engine attached to the carbs, nothing works right anymore. You would go on to mains size as big as the actual jet and it still won't run right.

And the reason why its getting worse the bigger the mains size I went is my stock fuel pump is having a hard time keeping up to fill all the 4 carbs and how they are now sucking fuel like mad with the mains size being 1.9mm!

So what I did is block the air correction jets with a tape, soldered my mains shut and redrilled to 1.2mm and boom!! PERFECT STRONG PULL ALL THE WAY TO 7000RPM!!!!

I won't make the habit of revving past the redline though LOL

Now to solder the air jets shut and I can say its done??

Minor tweaking here and there required but nothing too major now. At least I've got all the areas covered 95% perfect.

Oh and ordering proper sized pilot and main jets since soldered shut and redrilled jets just screams hackjob lol

IM SO HAPPY!!

[Hazwan]

Before blocking the main air correction jets and I'm on 1.8mm main size if I'm not mistaken. You can kinda hear the carb spitting just around 5k at 0:08 - 0:10 in the vid, indicating its running too lean. Also note how the sound changes note and distorted the mic a bit when the mains are kicking in (leaning out)



This is after I blocked the main air correction jets and went down on main jets size to 1.2mm. Pulls strong even with the filters on! Note how the sound doesn't change this time!


I've learned a lot from this project really. I can differenciate how running too lean or rich by sound, smell and feel alone. Lean sounded different than rich and stoich just sounds.. right.

[87roach]

Yay you figured it out! Great to hear man, the last video sounds very good, and strong too.

Get those proper sized pilots and mains and it's all good!

[AccordB20A]

im glad you have the time to muck with carbs. it really payed off too good work!

[MessyHonda]

so how is the MPG now with these carbs?

[Hazwan]

Still driving on a full tank. I would be happy if I get the same MPG as before and it would be better if I managed to get more since the CV carbs are supposed to be more efficient. It's so hard to drive without hitting the WOT now!! Still about 3/4 tank to go and I wanna see what its like with normal driving MPG