Bike revving high no apparent reason

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Bike revving high no apparent reason

Postby northman1 » 10:39 am May 18 2017

Hi, new to the forum. i bought a resto '87 KDX00, the guy did everything right but get the engine to run smoothly. Compression, spark, fuel\air at carb all check out. No funny cable routing. Carb was cleaned, stock jetted. No mods. It will start, run OK for awhile and then rev uncontrollably. All mechanical causes like throttlle, etc. have been checked. Suggestions for next step? I'm thinking crankcase leak but no evidence. New to this bike so any suggestions welcome. Cheers
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Re: Bike revving high no apparent reason

Postby david » 12:26 pm May 18 2017

Air leak. Check cylinder base gasket, intake manifold for cracks, reed valve gasket, crank seal under the fly wheel. You can spray some WD-40 in the suspected area and it should bring the idle down as the leak picks it up. Try using the choke to keep it from running away and don't let it run lean for too long, you don't want to burn up the motor. Others may chime in with other suggestions. Also check the fuel flow from the petcock. The strainer in the tank may be stopped up with junk and it can't keep up with the engine.

And welcome to the forum
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Bike revving high no apparent reason

Postby MotoLoco » 02:36 pm May 18 2017

First thought was air leak too. As said wd40 or such trick is great for finding where its at.
Fingers crossed for quick fix.
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Re: Bike revving high no apparent reason

Postby Jason » 03:18 pm May 18 2017

air leak

Also, A friend and I worked on his 1987 KDX200. The woodruff key sheared, allowing the flywheel to come out of time. It revved to the moon and we let the clutch out to get it to kill the engine. It would not stop just by the kill switch. In a state of panic, I had my thumb on top of his thumb on the kill switch! :lol: :lol: :lol:
THANK YOU, JulienD, for your ...waking out of a coma??
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Re: Bike revving high no apparent reason

Postby northman1 » 06:28 pm May 18 2017

Thanks guys. We found woodruff key sheared, magnets in flywheel loose. Anyone know a source for '87 KDX200 flywheel?
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Re: Bike revving high no apparent reason

Postby Jason » 11:04 pm May 18 2017

Sorry it turned out to be the same.

Check the stator coils for damage.

There was someone on eBay selling flywheel and stators. Another option is if you will search on here, some have had success to use a 1995+ flywheel and then mill out some slots in the stock stator plate. There are a few threads on it.
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Bike revving high no apparent reason

Postby northman1 » 10:15 am May 19 2017

Thanks everyone for the advice. Does anyone have a source for the follwing: 1987 KDX 200 - flywheel (21007-145) and carb boot (16065-1138).

Best,

Everett
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Re: Bike revving high no apparent reason

Postby david » 11:45 am May 19 2017

'81 KDX 175
'90 KDX 200
'07 Vulcan 2000 Classic LT (totaled 4/25/15)
'82 Honda GL500 (sold)
'96 ZXi 1100 JetSki
'98 STX 1100 JetSki
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Re: Bike revving high no apparent reason

Postby northman1 » 03:31 am May 20 2017

Thanks again everyone for the advice. Spoke with Jeff Fredette, I'm sending him flywheel and stator for re-build. He also has the carb boot in stock.
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Re: Bike revving high no apparent reason

Postby Jason » 03:33 am May 20 2017

Good luck on the rebuild. Thanks for keeping it going.
THANK YOU, JulienD, for your ...waking out of a coma??
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