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Strange problem with throttle staying open


Jedi Knight
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Hey y'all,
Haven't posted for a while, been reading posts, but can't believe it has been so long since I posted. Anyway, got an unusual problem.

The throttle on my 100M has been sticking open occasionally and got me stumped. Not all the time, could be cold engine or hot engine. Go to shift and engine revs stay up, not high enough to damage anything but not right. It will return slowly by itself so doesn't remain stuck open.

Checked to make sure it wasn't something very simple like gas pedal hanging up on the carpet or the pedal was sticking at the small shaft it pivots on. Everything okay there. Checked all the throttle linkage and nothing sticking there, spring on throttle shaft not sticking, and return spring connected and still "springs" okay. Linkage is relatively stiff but always has been. Checked the carbs, cleaned up the pistons, checked oil level in damper assembly. Even ordered new springs for the pistons/chamber assemblies but those are not in yet as just ordered. Hoping, that might be it but any ideas ???

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... ordered new springs for the pistons/chamber assemblies but those are not in yet as just ordered. Hoping, that might be it but any ideas ???

Doubt that's the cause of the problem; this sounds like the throttle plates are being held slightly open for some reason. Suspect something is binding; either in the carb-to-carb linkage or in the throttle linkage. Just reworked the throttle mechanism on my BJ8; it's possible, if the linkage isn't adjusted correctly, for the the linkage to bind up in an 'over center' position (but not particularly likely). If I had to guess, there's gunk or a worn bushing(s) in the throttle shafts. I have a BN2/100M as well, and never felt the coaxial return springs did a good job of returning the throttles to closed; when I let off the gas pedal, sometimes the RPMs will drop to an above-idle speed, then gradually slow down.
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How's the throttle shaft to bore fit? If the shafts are worn, they could allow enough misalignment for the plates to get slightly cocked in the throats, dragging to the closed position.

That's something you can check when you open them up to replace the damper springs.


Jedi Knight
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Thanks Randy and Bob - I'll let you know after I replace the damper springs as well as main return spring if it solves the problem or do I need to look into your suggestions. Don't think it is gunked up as have sprayed enough carb cleaner on the linkage to qualify for an EPA superfund site !


Jedi Knight
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Well y'all,got new damper springs and a new return spring and has helped but still seems to stick sometimes. Not as bad but suspect it's a combo between what Randy and Bob have said. Guess next step is to take the cold air box off AGAIN, and double check all the linkage and see if it is binding somewhere. Will let you know what solves it.
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