87 idle speed

[Jhonno]

My 87 classic is dedicated gas, no ecu present, still has original plenum, fitted with an impco 200.

My problem is that I can't get the idle below about 11/1200:(, (cold start 13/1400). Have moved the small allan headed screw under the throttle stop so it no longer touches, made sure the accel cable has slack, tried adjusting the air screw (I think thats its name) on the mixer??? Rechecked diaphragm and plate, severely bent during early backfiring episodes:eek::eek: On the odd occasion after a run she will idle perfectly around 600, when the air con is switched on the idle increases to compensate, haven't really paid attention to see if this happens when the idle is high.

Right from the outset she has caused me grief but slowly the problems are diminishing, no more backfiring, the rest aren't relevant to this forum and I hate crying.

Any help with this annoying problem would be greatly appreciated.

Thanks John

[bee utey]

My 87 classic is dedicated gas, no ecu present, still has original plenum, fitted with an impco 200.

My problem is that I can't get the idle below about 11/1200:(, (cold start 13/1400). Have moved the small allan headed screw under the throttle stop so it no longer touches, made sure the accel cable has slack, tried adjusting the air screw (I think thats its name) on the mixer??? Rechecked diaphragm and plate, severely bent during early backfiring episodes:eek::eek: On the odd occasion after a run she will idle perfectly around 600, when the air con is switched on the idle increases to compensate, haven't really paid attention to see if this happens when the idle is high.

Right from the outset she has caused me grief but slowly the problems are diminishing, no more backfiring, the rest aren't relevant to this forum and I hate crying.

Any help with this annoying problem would be greatly appreciated.

Thanks John
Two things control the idle speed, not the throttle stop. First is the base idle screw (3/16 inch allen key) in the top of the throttle body area. Second is the thermostatic idle control valve in front of the manifold. Either way you shouldn't ruin the idle mixture by leaning off the screw on the mixer.

[Jhonno]

Thanks I'll check it out as soon as the 93 is up and running from the service station at Coolongalook

[willvine]

Hi mate I have the same set up on my 88 classic. Check all the vacuume lines and connections on the plenum as leaks will cause extra air to be sucked in. This is what i found when i had the same symptoms.

Cheers Will.

[Jhonno]

Thank you, more things to try as soon as the knee allows, I'll be putting them to the test.