It just wont rev out

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It just wont rev out

Postby ridinredneck » 08:36 pm Jan 17 2015

i picked up an old 98 kdx200 recently. it needed a cdi box to run. got one for it and sure enough it fired right up. but it has a rev problem. it simply will not rev past 1/4 throttle. i have rejetted several times, tried different needles, put new reeds in, checked the power valve ( its working), fresh gas and cleaned the carb. it starts 1st or 2nd kick every time and idles great. compression is good it just wont rev out. it sounds like it is hitting a rev limiter. just ding ding ding ding. i noticed it has an exhaust leak where the pipe goes in the cylinder. the copper gasket and o-rings are there but it still has a leak. would this cause it to run like that? or any thing else to check.
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It just wont rev out

Postby canamfan » 09:27 pm Jan 17 2015

Have you checked the silencer, to see if it is plugged. If it is, it could cause your exhaust leak. To much back pressure. Also is the cdi box the correct one for your bike, could be retarding the spark at higher rpm's . Make sure the plug wire and cap are in good shape.
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Re: It just wont rev out

Postby ridinredneck » 09:37 pm Jan 17 2015

it is rather quiet out the silencer so i will check it to see if its plugged any. i can see a little smoke but not shooting out like it should. mostly just kind of rolls out. the spark plug is new and the cap looks good. the cdi was listed as for a 95 model. should be the same as a 98 model right?
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It just wont rev out

Postby canamfan » 11:32 am Jan 18 2015

I would think the cdi would be good. H series should be all the same. Quick check for the silencer, just pull it off and see if it revs.
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Re: It just wont rev out

Postby dingerjunkie » 12:51 pm Jan 18 2015

As crazy at it sounds, perhaps check the silencer itself. The KDX250 I picked up running was a foul mess...both the silencer and the chamber had standing fluid (oil spooge)...easily over a pint between the two. The motor was literally bubbling through oil to try and run.
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It just wont rev out

Postby ridinredneck » 01:37 pm Jan 18 2015

to all those pointing to the silencer, you were right. cleaned it out and revs right up. now i have to go back through the jetting again lol.
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Re: It just wont rev out

Postby KarlP » 09:46 am Jan 19 2015

'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
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Re: It just wont rev out

Postby Jason » 12:04 pm Jan 19 2015

Wow.

glad you got it going
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: It just wont rev out

Postby ridinredneck » 05:55 pm Jan 19 2015

KarlP wrote:It happens:

viewtopic.php?f=110&t=4485


glad to see im not the only one lol

and thanks jason
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