idle problems

[thrashin88]

hey everybody, heres a little background. i got a 1980 gs 750 for $100.00 from a friend that was chopped into a hardtail but never finished so i got it in parts. the airbox wouldnt fit anymore so i used a dynojet kit to rejet the carbs for pod filters and the bike finally runs and drives good with full power through all the gears. the question i have is this... basically the idle seems to fluctuate a bit. for example, today i started it and got it warmed up and the idle seemed to be solid and i went and drove it for about 10 minutes and when i pulled back into the driveway i stopped and for about 10 seconds the idle stayed nice and low (about 800-1000) and then it slowly started revving up to maybe 1500-1800. it seems to do this alot. also if it starts idling low and i turn in the idle screw a tiny bit sometimes it will do the same thing and start revving up. i refit the boots to stop any potential leaks and it seemed to help but its still not perfect. i also synched the carbs at the same time i did the boots but i did it with a kinda ghetto homemade carb sync so its still not perfect but its better than it was. could a legit carb sync fix this or should it be something else? thanks, i could use ideas.

also just for fun... on the front of the engine theres a spot where it seems to be leaking a little bit of oil out of the head gasket right in the middle where that little bolt is. is this a problem? i know its an old bike so if its not a big deal im not worried about it, i just wanna drive the thing. also the pipes i have are 4 into 2 and the pipe for the right 2 cylinders has oily residue in it. should i be really concerned or is it normal for a bike this old to burn some oil. thanks again, you folks are lifesavers

[nisom512]

hey everybody, heres a little background. i got a 1980 gs 750 for $100.00 from a friend that was chopped into a hardtail but never finished so i got it in parts. the airbox wouldnt fit anymore so i used a dynojet kit to rejet the carbs for pod filters and the bike finally runs and drives good with full power through all the gears. the question i have is this... basically the idle seems to fluctuate a bit. for example, today i started it and got it warmed up and the idle seemed to be solid and i went and drove it for about 10 minutes and when i pulled back into the driveway i stopped and for about 10 seconds the idle stayed nice and low (about 800-1000) and then it slowly started revving up to maybe 1500-1800. it seems to do this alot. also if it starts idling low and i turn in the idle screw a tiny bit sometimes it will do the same thing and start revving up. i refit the boots to stop any potential leaks and it seemed to help but its still not perfect. i also synched the carbs at the same time i did the boots but i did it with a kinda ghetto homemade carb sync so its still not perfect but its better than it was. could a legit carb sync fix this or should it be something else? thanks, i could use ideas.

also just for fun... on the front of the engine theres a spot where it seems to be leaking a little bit of oil out of the head gasket right in the middle where that little bolt is. is this a problem? i know its an old bike so if its not a big deal im not worried about it, i just wanna drive the thing. also the pipes i have are 4 into 2 and the pipe for the right 2 cylinders has oily residue in it. should i be really concerned or is it normal for a bike this old to burn some oil. thanks again, you folks are lifesavers

if you didnt rebuild the carbs before you got the bike running I would do so. check float levels as well.

Go here for a picture walk threw

http://members.dslextreme.com/users/bikecliff/

Then get intakeboot o-rings(the likely solution to your problem) along with a carb o-ring kit as well. you have CV carbs also known as BS carbs

http://cycleorings.com/

Good luck

Jake

[thrashin88]

the bike i have doesnt have intake o-rings, they are just rubber boots that clamp the carbs on one end to the engine on another, its a 1980 thing i think. and those look really new, they arent dry, cracked, or worn in any way but i still think its possible they still might not be getting as quite good of a seal as i want. is there some kind of sealant that i could put around the inside of the boots to make sure im getting a good seal? cause somewhere along the line it seems to have a leak unless theres something im not thinking of

as far as the float levels go... could that affect the idle fluctuating? as i understand it that shouldnt affect it but im no expert by any means?

also could a legitimate carb sync possibly help this. i just used a homemade 2 carb sync device to sync all the carbs to number 3. (1 to3, 2 to 3, and 3 to 4)

[almarconi]

as far as the float levels go... could that affect the idle fluctuating? as i understand it that shouldnt affect it but im no expert by any means?

The float level/ fuel height will have an effect on all the jets of the carburetor.

Sounds to me like you have some air leaks. Take a can of carb cleaner and spray your intake and exhaust boots. Listen for changes in the idle. The carb boots have a right and left, they must be oriented correctly for everything to seal. If they are old they should be replaced.

The vacuum sync will effect the way the carburetors perform. Sync the carburetors correctly. If you don't have the right tool, either borrow one or pay someone to do it for you.