I'm going on a low carb diet

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texas-ss-tornado

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Working on an 85 with 27K miles, hasn't run good since I got it. I bought a set of 85 carbs off ebay and rebuilt them, top to bottom. Did everything the right way, got alot of help from Danny along the way. Got them all together on the bike, and it's still running like crap. It's like the back two cylinders are not firing (1 and 3), I can put my finger on the header pipe and not get burnt. Front two are much hotter. Bike just doesn't rev for $hit and won't idle. This is pretty much how the last set of carbs acted on this bike, which led me to try another set. Now I'm thinking it's something else. What would cause 1 and 3 to go out at the same time, they don't share the same coil? I tested spark on 1 and 3 and it's bright and happy, the funny thing is one of the plugs I pulled, 3 I believe, was wet, but even after I put a new one in it and made sure it was sparking, the cylinder is still not getting hot. I'm stumped. Everything points to carbs. Again. I'm about ready to give up and just send them off to Danny and have them put on his test bike setup. They are all stock except I put 150 mains in it. Stock airbox and 4 into 1 Holeshot exhaust. These old bikes sure keep you on your toes though!!!! Any advice would be greatly appreciated!
 

tugla

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while you are at it a compression test would be good info.

if you rev it up will those cyclinders or pipes starts to get warm??
 

Blurr

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while you are at it a compression test would be good info.

if you rev it up will those cyclinders or pipes starts to get warm??
Took the words out of my mouth, virbetum.
 

run990

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as the bike has not responded to the usuall subjects,how about loosening the rear cylinder exhaust pipes ,see if the collector box as collapsed blocked baffles.has the bike had a new flywheel starter clutch fitted.the early 2 pickup & later single ones probably vary.you will be getting a spark but it could be at the wrong time.
sit back go to basics,check cam timing roughly with carbs off & plugs out ,do a blow down compression test.you can check crank pickup position to piston position & visa versa.
from my reply you can guess i am always the one who gets the problem bikes to fix at work.dont get tunnel vision re carbs,if it does not fire on the cylinders after squirting a bit of fuel down the carb whilst its running its not fuel.
above all dont discount anything ,i spent a week on a scooter that kept cutting out,problem a faulty brand new yamaha air filter.
 

texas-ss-tornado

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I don't know, I've tested both rear cylinders with spark plugs outside of the bike, looks like a good spark to me. I have heard a few backfires here and there though, so who knows. I'll just have to keep troubleshooting, thanks for all the suggestions, keep em' coming!
 
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