Idle Issue

[Jimmbuzz]

I have 1982 GS750T (TSCC). Carbs have been cleaned/rebuilt by a local shop. Bike starts and runs ok, but while riding, the idle likes to creep up to 3000 rpm when I come to a stop. I usually turn back the idle screw and set it back into range, but by the next stoplight/sign, it will have crept up again to around 3000. I don't usually have to turn it back when starting the bike. The only other issues I'm currently aware of is a head-gasket oil leak, and an oil plug leak, which I plan on addressing both later in the summer with an engine tear down and rebuild. I would like to weed out this issue before then. Any suggestions to what could be the cause is much appreciated. -Thanks

 

[Big T]

Air leak at the carbs is causing the rising idle

Did you install new boots and O rings?

As to the oil leak at the head, degrease the motor, spray with foot powder, start the motor and trace the leak

Much more likely to be the valve cover gasket than the head gasket.

 

[tom203]

Welcome aboard... disturbing the carbs (to hopefully clean them properly) probably left the intakes pipes /clamps unhappy. Did your shop replace them? If they leak, you'll get this issue of increasing idle as engine warms.
See part# 22 and 23 in this layout . 37 yearold rubber parts are suspect

https://www.partsoutlaw.com/oemparts/a/suz/50d400abf8700230d8b4e32e/cylinder-head

 

[Jimmbuzz]

I do believe you are correct. I just sprayed some carb cleaner around each boot while it was running and I did get some change in rpm so that must be it. Thanks!

 

[Steve]

Air leak at the carbs is causing the rising idle

Did you install new boots and O rings?

I agree with the air leak concept, but his bike does not have o-rings. :-k

The port in the head ends up as a cast tube, there is a simple rubber tube (hose) that joins that with the carb output.

.

 

[Big T]

Yes, but O rings would include the carbs