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Bike Revs Slightly At No RPMs/Low RPMs

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I just picked up a 1998 RM250.  If I lay off the gas, and coast while in gear the bike sort of "jumps" a little every second or two.  It just kinda jerks a little.  When I'm idling, it does the same thing and kinda jerks a little as well.  It's not revving up crazy like an air leak, just sorta jerking until you give it some gas then it's fine.  Not real sure whats going on.  I'm gonna rip the carb apart and clean it out and see if that helps.

 

I was messing with the choke and didn't realize that rotating the knob affects the idle.  It didn't do it before I messed with the choke knob (at least not from what I remember).  Can't really remember perfectly as I've only  had it 30 hours now.  

 

 

Any help would be greatly appreciated!

 

If you need me to get a video of it to show you what's going on I will, but I assume that I'm not the first person this has happened to, and I'm assuming someone knows how to fix it LOL

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I'll add this bit of info.  The previous owner ran 36:1 and I mixed at 32:1.  I don't know if this could cause the problem or not since it was jetted to run at 36:1 but figured I'd add that info.  I just pulled the plug and noticed it's pretty wet.

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so the bike jerks while you're idling ? do the rpm's pick up when it jerks ? or do the rpms stay leveled and the bike jerks on its own ?

 

if the rpm's don't pick up i would be looking at the clutch and the clutch actuator

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The rpm's go real low, then it jerks as they come back up a little, real low, jerks as it comes back up.  It's almost like it's trying to stall, and then it kicks back up to idle and that's when it "jerks".  

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Check for any obstuctions in and around the chain, the rear wheel and both sprockets first

 

second check the slack on the clutch cable, you gotta have it just right where it disengages and engages cleanly without any gaps in friction

 

next suspect clutch assembly if all else fails gonna have to pull the clutch cover and check the plates

 

also make sure air/idle screw is properly adjusted put it on the lowest setting

Edited by 78SuzyQ

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Well, the guy I bought it off of just installed new Tusk clutch plates.... if that tells you anything...  

 

Guess I should have mentioned that earlier.

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I'll check the air screw in the morning.  It's 1 1/2 turns out for the air screw, correct?  Also, how should I adjust the choke knob... is there a set number of times that i'm supposed to turn the knob to adjust the idle specified by Suzuki?

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Well, the guy I bought it off of just installed new Tusk clutch plates.... if that tells you anything...  

 

Guess I should have mentioned that earlier.

 

 

tusk ? isn't that knockoff ebay garbage ? that could be the main thing that the plates are just garbage or it could be he changed the friction plates and not the springs i always go with oem

 

but if the clutch plates are slipping then grabbing  at low rpm / idle then it could be a mix of problems could be theres anti-friction lubrictation in there, could be the clutch isn't compressed enough, poor quality plates etc.

 

theres an old trik where you take spark plug washers and you put em down underneath the clutch springs it preloads the compression and cures slipping

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As far as I know tusk is quality stuff.

I just noticed the gear oil was a little low. I'm gonna get some bel ray in the morning.

The problem happens even in neutral, would that still be a clutch problem?

Sorry for all the questions, just wanna make sure I do everything right and get it running the way it should be.

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hmmm not really familar with this problem someone with a little more expertise may know but i've had issues before where the bike would be slippin in and out of neutral like it's caught between both neutral and first or neutral and second and it sort of sticks in and out. Also see if the jerking is affected by leaning the bike to each of its sides lean it down to its left then lean it down to its right see if it affects the jerking.

 

That's all i know i wouldn't be able to tell unless i actually looked at it

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