I have to Idle down as it warms up

[austincaferacers]

Ok, i have a 77 Suzuki Gs750. The carbs are clean and last week i put in new floats and all jets are to spec and floats are set right. Before i put in new floats, the bike would surge and spark plugs would be a dry black chalk color and my bike would bog down after an hour or less of riding and i couldnt ride it far unless i put in new spark plugs each time.
But now with the new floats it doesnt surge up to 5 or 6 rpms anymore and sounds good. But it will idle up to about 2 rpms after a few blocks and i will idle it down to 1.5 or 1. It does it every time i ride a street then stop. I havent ridden it long enough to see if it ever levels out. Is this normal in a bike 30 years old? I just put in new spark plugs gapped to speck and new oil filter and oil too. Thanks for any reply.
One more note. Before i put in the new floats last week, the bike would leak gas. About as much gas as would fill the float bowls. So i attributed it to the bad floats. Well today i noticed gas on the ground, about a 1 ft radius of gas, but my bike was on a slight down grade. The front of the bike was facing uphill. Was this just the gas sitting in the float bowls leaking into my airfilter box then onto the ground? Is that normal too?

[bwringer]

Rising idle speed as the engine warms is a textbook sign of an intake leak and/or too-lean mixture caused by removing or modifying intake and/or exhaust parts without rejetting to match the revised airflow.


What is normal for 30 year old bikes is to run like raped apes. Don't accept crappy carburetion just because the machinery is old. Your GS should start instantly in any weather warm up quickly, idle smoothly, and run hard all day, every day. If it doesn't, something is wrong.

[jabberjoe87]

there is a link on basscliffs website with four steps to tuning carbs. One of these steps involves teh float height

[austincaferacers]

Exaust mods

So you say an intake leak or modification to the exaust could cause this problem. The previous owner did put a silencer, i think thats what it is, on the end of the stock exaust pipe. COuld this cause the bike to idle up slightly? Also, the tightening clamps around the carb to the airbox and carbs to the engine dont exactly get super tight. I take it that i should be able to tighten completely with room to over tighten? At this point, they dont exactly tighten down as much as i think they should.

[austincaferacers]

So you say an intake leak or modification to the exaust could cause this problem? The previous owner did put a silencer, i think thats what it is, on the end of the stock exaust pipe. COuld this cause the bike to idle up slightly? Also, the tightening clamps around the carb to the airbox and carbs to the engine dont exactly get super tight. I take it that i should be able to tighten completely with room to over tighten? At this point, they dont exactly tighten down as much as i think they should.

[BassCliff]

Hi Mr. austincaferacers,

Please re-read the mega-welcome, paying particular attention to the "Top 10 Common Issues".

Sometimes, if a bike has been neglected for a while, you just have to do all of the proper maintenance up front. Then you won't be forever chasing down all kinds of pesky little problems.

Did you follow the carb cleaning bible religiously? Did you bench sync the carbs? Is stock airbox attached? Are there absolutely no leaks in the air intake system (i.e. new boots, o-rings, airbox sealed)? Keep us informed.



Thank you for your indulgence,

BassCliff