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Discussion Starter · #1 ·
just rebuilt my engine and it's running ok, but... dies when revs are low. even in neutral, clutch disengaged.

i have to keep my hand on the throttle when slowing down/braking for lights, bit tricky.



probably something to do with the pilot jets on the carbs but wondered if someone has had this before and knows the exact fix.



cheers
 

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Might be electrical. Had this problem on another bike when the rectifier went bad. Does it charge okay?

Otherwise, where does it idle when it's warmed up? Or does it just die? If the electrical seems okay, maybe set the idle high, and slowly lower it. Maybe it's set too low?
 

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It could also be a vacuum leak. Does your bike have a vacuum-operated petcock? If so, check the vacuum hose between the carbs and the petcock for splits at the ends or other leaks. On occasion the petcock can develop a vacuum leak but still seem to operate normally otherwise.



What kind of bike do you have? This would be good information to have in everyone's signature.
 

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Discussion Starter · #4 ·
Thanks for the replies guys




Might be electrical. Had this problem on another bike when the rectifier went bad. Does it charge okay?

Otherwise, where does it idle when it's warmed up? Or does it just die? If the electrical seems okay, maybe set the idle high, and slowly lower it. Maybe it's set too low?


think the electrics are ok, not checked voltages but will tomorrow. battery hasn't ran out yet but it's only been a few days. have had to keep restarting it (30 times a day) so it must be charging or it would be dead quick (it's a cheapo one)

yeah I think I have to adjust the idle setting, need to do my research on that. if i leave the choke out full on startup, it runs fine at about 1600 and will even run for a bit when I put it back in again too - but once I get going it won't, unless I keep the revs up.





It could also be a vacuum leak. Does your bike have a vacuum-operated petcock? If so, check the vacuum hose between the carbs and the petcock for splits at the ends or other leaks. On occasion the petcock can develop a vacuum leak but still seem to operate normally otherwise.



What kind of bike do you have? This would be good information to have in everyone's signature.


it does feel like it's running out of fuel, mines a '79/80 Z think it's the earlier petcock without the vacuum ? the rubber hose between the tank and carb doesn't leak, but I've got no clips on it atm, so will get some and check if that helps.



really want to strip the carbs down, but only source of good carb bits seems to be Randakks in the US and I'll need to wait a while for postage. not sure if I can re-use old gaskets with some sealant in the meantime. will also check the plugs and compression readings tomorrow.
 

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I had a similar issue and it was dirty carbs for me.  Could be the low speed jet is partially blocked, or just generally dirty carbs.  If you're careful you can take the carbs apart and reuse your gaskets, somebody just posted about how they used Pinesol to clean their carbs with the rubber bits still in them.  In the mean time you could maybe just turn up your idle speed so you don't have to worry about stalling.  Do you have an inline fuel filter between the tank and carbs?
 

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I've run into that behavior when the carbs are out of sync. It'll tick along just fine until you get low enough that one cylinder cuts out, then it's over. Just a thought --
 

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Discussion Starter · #7 ·
thanks again. makes sense. would try the pinesol trick, but can't buy it here. will turn up the idle, bidding on a spare set to rebuild atm. might have to experiment with the diy vacuum balance rubber tube contraption.
 

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Good thought about sync.



If the bike runs fine and has enough fuel at higher rpm under load, it certainly would have enough at idle/rest.



I'd think one of the idle circuits is plugged.
 
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