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Discussion Starter · #1 ·
Hi guys, I'm hoping someone can help me out a bit...

I've just bought a 55 plate 250 excf, awesome bike, runs like a dream...or at least it did! It's developed an annoying throttle glitch that once you shut off the revs don't drop down to idle speed but stay, sort of half revs (very annoying when you're heading down hill on a tricky bit and need engine braking!).

It gets better when I adjust the idle thumb screw (down), but then the bike stalls when I pull the clutch in to stop! All very very frustrating.

I've got an idea it may be a combination of a glitch with the carb and/or valve clearances...? I've also heard lots about this JD jetting kit?

Just wondering what you guys think...if anyone can shed any light or give me a few pointers, I'd really appreciate it.

Cheers
 

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Is the carb slide returning?? or sticking? needle worn or bent? Check main jets etc as well.
I dont have the JD kit, but its worth maybe contacting them, they may be able to advise a bit. If it was me I would sort it asap, if your coming over here, you dont want to `sling it away` and end up hurt

I had a very simular problem recently and it turned out to be a worn throttle tube!! I replaced the throttle tube assembly , now perfect, but from what your saying it may be the carb itself... I hope this helps, but there are many other more experienced guys here that will also advise I am sure.
 

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Discussion Starter · #3 ·
Thanks excman. I think I'm swaying towards taking the carb apart and taking a proper look before buying any kits or sending it in to get the clearances done.

Can't wait to visit your fair isle, be the 5th time, and the lanes keep getting better :D
 

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Make sure the plate in the slide is the correct way up, should look like this
 

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Discussion Starter · #5 ·
kevinyorks...thanks mate, pics and everything!

Is this a common thing to be wrong? Presumably the only way this could happen is by some numpty putting it in the wrong way??

Thanks again mate :)
 

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Yup, numpties not watching what they are doing ;)
 

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sounds to me like its ur mixture screw (underside of carb) start with it at 1 1/2 turns out and work ur way inwards a 1/4 of a turn at a time till u get it right ( ride it after each adjustment dont just fire it up and expect it to be right as the carb needs time to adjust to a different setting ) its a bit tedius as i know from personal experience but when u get it right its happy daze! (a good idea if u can get 1 would be a aftermarket mix screw that u can adjust with your fingers instead of twisting the carb to adjust the original screw unless u have the special tool to do it whilst the carb is insitu. hope this makes sense and helps . regards walesy1
 

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It might be stating the obvious but have you got both throttle cables fitted and are they free under the tank. Always start with the obvious and simple to rule things out.

If two cables are they adjusted correctly!
I tend to adjust with a touch of slackness, easy for the pull open side but I insert the tip of a screw driver between the stop and the cable cam tang to adjust free play for the return. (With the idle screw wound out so the slide bottoms)

Whip the air filter off and check to see if the slide does fully close.
Check the slide plate as Kev says; although the symptoms would of been there at the start; how long you had the bike in hours.

Just a few for starters, hope its of some use.

Cheers Nick
 
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