engine idle

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johnbirchjar
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engine idle

Post by johnbirchjar » Sun Dec 24, 2017 10:56 pm

Hi guys(honest,fitting this Commander engine in the Classic frame is quite a project evil)anyway,I am having trouble getting the engine to idle at 800rpm without "Hunting"(and this causes the transmission to snatch when trying to just trickle along on a whisper of throttle,)If I open the throttle just a wee bit(and I do mean "a wee bit")to a 1000rpm the engine idle is lovely and smooth(just like an air cooled)but I can't seem to get the same responce using any other methode,I get no response AT ALL from the "idle screws",ditto with the Idle Rod,If I use the Throtle Cable adjuster I get the desired result,but the revs rise alarmingly when the handle bars are on full lock to the left,so that's a no go,using the Throtle Cable raising the revs to about 1200 and adjusting the mixture screws also has the desired affect,but setting the Throttle Cable back to where I get no responce on left lock the revs return to 800 and Hunting evil,and before you ask,I have replaced every single "O" ring in the Carburation system cool.
I have an IP2 W/Shop manual which explains how to set the Carbs,so I assume the method is the same for Commanders?
After all the thousands of miles (and the occasional Carb "Tweek")with the Classic I thought I had the old SU's well sussed,
obviously not exclaim,so what am I doing wrong? advice please,I am a very frustrated roterian,J.B.

fogrider
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Re: engine idle

Post by fogrider » Mon Dec 25, 2017 12:31 pm

Hi John, I had all this with my F1 Sport, by the time I had sorted it, too late to get her to the Manx, it sounds just the same and it was all down to air leaks. I'm not familiar with the Commander set up ,but if the idle screws were not playing on my Sport it would be air leaks for sure. I replaced all the O rings but it was mainly the idle by-pass pipe rubbers, carbs to plenum chamber (distortion) and intake tube sleeves. Carb settings for idle become way too rich with just a slight air leak, that cocks everything else up.
Sounds like the slack in the cables and the cable runs also need a sort, instant Mot fail if the revs change on handlebar movement.

I ended up stripping it all off again and going through it looking for things I had missed by assuming " it must be OK, it looks OK."
Put right everything I'd missed , re-set the carbs and away she goes.........
keep at it,
Regards, Terry.

johnbirchjar
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Re: engine idle

Post by johnbirchjar » Tue Dec 26, 2017 1:31 pm

Hi Fogrider,Thanks for confirming what I already suspected that it was all down to air leeks evil.
In the new year I shall buy and fit all the necessary "O" and rings and pay particular attention when re-assembling twix Carbs and Chambers.
Resetting the Throttle Cable was not a problem,full left lock and screw the cable back in till the revs were at Idle Very Happy,I shall report anon,ride safe,J.B.

johnbirchjar
moderator
Posts: 1117
Joined: Sat Mar 07, 2009 11:20 pm

Re: engine idle

Post by johnbirchjar » Tue Dec 26, 2017 1:32 pm

Hi Terry,Thanks for confirming what I already suspected that it was all down to air leeks evil.
In the new year I shall buy and fit all the necessary "O" and rings and pay particular attention when re-assembling twix Carbs and Chambers.
Resetting the Throttle Cable was not a problem,full left lock and screw the cable back in till the revs were at Idle Very Happy,I shall report anon,ride safe,J.B.

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