weird airbox short circuit..

full vac removal on carbed 86

was out driving last night for about 45min, about 1km from home engine cut out dead, try the key and it would just crank and not start at all, couldnt see anything so i just walked home.
went to have a look this morning, pulled off the airbox checked that fuel was getting to the carb etc, started first crank... but then the weird started happening...
it was idling so i grabbed the airbox to put it back on the carb while it was running, and bigish shocks of electricity when up my arm and the engine started to stop, so i pulled it away and it idled again, a little stupidly i did it again to make sure i wasn't just losing my mind, and yep theres a short circuit somewhere that somehow my airbox is making. but i got a old t-shirt outta the car wrapped it around the carb and drove it home, it starts and idles fine, until you put the airbox on then it just cranks over continually.

from what i can tell with how it feels like the spark / dizzy elec which is shorting, but i have no idea how or where, or why it started so suddenly in the middle of driving

any advice would help alot

Cheers

you dont have an HT lead touching and rubbed through do you?

x2 on plug wires. When were they last changed?

finally had a chance to look, and yas pointed me in the right direction, was looking for wear (looks like origonal leads ;o ) couldnt see any, but when i pulled off the lead between the dizzy and the coil, there was alot of corrosion in the dizzy cap, cleaned it out as much as i could and bought a new lead, works fine now, thanks for advice

but i was wondering is it common to get corrosion in there ? i used a bit of petroleum jelly to stop it from forming again

It's a best practice to use silicone grease on all wiring connections to prevent corrosion. Twenty year old wires are going to fail in some way. The connections aren't water proof, so corrosion is a possibility. Just monitor the new wire to make sure it doesn't happen again and make sure to follow the maintenance schedule to prevent outlier failures like this in the future.