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Discussion Starter · #1 ·
hi Guys, Hope someone out there knows what the problems are on my newly aquired bike. This is a track bike that I just picked up and there is no engine modifications other than the carbs being Jetted. I asked the owner what type of jets were installed and he was not sure only that it is not a Dynojet kit. He did say though that the guy who did it, jetted the $hit out of it. With that being said..Here's the symptoms.

Being it's a carb bike, I apply the choke to start it. It idles there for a second or two then dies. I then have to restart it. I have to do this at least 10 times before it'll sit and idle by itself, all the while the choke is still FULLY on. ( Wierd since most jetted bike, you don't need the choke to start it) If I try to take off the choke, it'll die. I let the bike warm up for about 10 minutes. With the choke still on I roll on the throttle. It bogs down a little then picks up ONLY if I take off the choke. Once the choke is fully off, I can rev the bike. But as soon as I roll off the throttle, it'll die if the choke is still off but will remain running if I put on the choke. Wierd huh? :headscratch

Do you guys think it's an air issue? gas issue? vaccum issue? carbs needed to be synch or cleaned or both? Not quite sure what it could be but I know someone out there has to know how to troubleshoot this. Someone please help before I lose my mind trying to figure this out. :banghead

Thanks in advance guys!
 

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Hmmm this rings a bell, vapor lock?? timing may be out.... actually that is something to check, being a race bike he may have advanced the timing also did he put a new can on it for street?
 

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Discussion Starter · #3 ·
slim1100 said:
Hmmm this rings a bell, vapor lock?? timing may be out.... actually that is something to check, being a race bike he may have advanced the timing also did he put a new can on it for street?
Slim1100, I contacted the previous owner and asked him what was done on the bike. He replied with saying that the motor was stock except for the carbs, which were jetted. The jets though are not Dynojets. They are something else and he couldn't remember the name of it nor how big the jets were. He did say that the guy who did it, jetted the shit out of it. I don't think it's vapor lock as the bike will run when you start it, but then quickly dies. I have to restart it about 5 times before it'll stay running with the choke fully on. Once it warms up a bit, I can rev the motor as long as I take off the choke. If I let go of the throttle after revving, and the choke is off, it'll die so I have to quickly put the choke back on for it to idle. Doesn't make sense to me. What do you think?
 

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Dangeris
Do you know if the bike sat for very long without being run? It sounds like the some of the jets may be partly plugged. This can happen over time due to build up of varnish caused as the gas in the fuel system breaks down. Can happen in as little as two to three weeks.
 

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I would say you are experiencing a fuel issue.
Bike is running too rich and flooding out the cylinders when throttled.
However, when was the bike running fine last? This might help disprove the idle circuit
 

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The first step is to find where the engine is running poorly...which you already know at this point. Carb jetting is determined by the throttle position, not engine speed. If the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem.
Here is a chart breakdown.
 

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if a bike is running too rich how do you adjust that. I think I am having issues with my bike running too rich. Would you guys put fuel/carb cleaner in the tank or clean the carb or just adjust the fuel/air settings?
 
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