Idle raises the longer I ride?

[tommyz24]

Hey guys , a few rpm problems here. After I start the bike and let it warm up with no more choke, it will idle at 1500. After I ride around for a while it will start to raise up slowly 1750 then 2000 ..2200 up till about 2400/2500 rpm. It will continue to hang and not move higher or lower. Is this just an idle adjust or something else. 2nd what is the best way to adjust and idle on a gs400.

[tom203]

Hanging idle is often caused by air leak in area where carbs connect to head- leaky o-ring, damaged boot, etc. Your idle will not be stable till you ensure a tight seal.

[mike_of_bbg]

Hanging idle is often caused by air leak in area where carbs connect to head- leaky o-ring, damaged boot, etc. Your idle will not be stable till you ensure a tight seal.

Yes, this ^^^.

Also, that cold idle is too high at 1500. Should be more like 1100, but check the spec for your model, maybe the twins are different (I thought the spec was 1100+/-100 for pretty much all models though). There should be an adjustment knob between the carbs.

See part #41:

[Nessism]

Read this...http://www.thegsresources.com/_forum...d.php?t=171846

[tom203]

Confusing parts fiche layout, try this one (for 1978 ). lots of places for air to leak in at carb/head interface

http://www.alpha-sports.com/spst/1978%20GS400/01.htm

[GS(X)400]

If you have not reached the carb boot and carb boot orings do that.

[tommyz24]

thank you very much gents

[tkent02]

First things first. Get the engine good and hot, then adjust the big idle screw to 1,000 or 1,100, whatever RPM the manual advises. When the engine is still a little cold and the choke is off it will likely idle a bit slow, that's kind of how they roll. You can either leave the choke on a little bit until you get going down the road, or hold the idle a little higher with the throttle until it's warmed up enough to idle well.
Do the other adjustments also if you haven't done them yet, valve clearances, carb synch, and idle screws for a start.
You may have intake leaks, maybe not. Sometimes everything being just a little out of whack can act like an intake leak.

[BassCliff]

Hi,

CLICK HERE. How many of these maintenance tasks have you completed?

All carb adjustments, main idle, vacuum sync, etc, should be done when the engine is up to full operating temperature. Make sure your intake system has no air leaks, airbox, intake boot O-rings, etc.


Thank you for your indulgence,

BassCliff