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KTM 380 EXC runs 'full throttle'!!

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Hi all . . . I've got a question that maybe you can help with - Got a 98 KTM 380 EXC that's running at full throttle at times when warmed up - (with throttle off - only way to stop it is with the clutch - kill button is useless when the RPM's are up there) Just finished putting this back together, so the maiden voyage has been maybe 1/2 mile, before it started to rev out of control! - I replaced the intake, reeds, both crank seals (flywheel & trans side) clutch, pretty much everything over the last year - (This thing is FULLY restored, & mint) - It's street legal, but I can't seem to get this over-revving thing figured out - Could it be a carb issue, or an air leak from somewhere? Also seems to smoke excessively, (running 50-1 mix) & won't run smooth at lower RPM's - Any advise would be MUCH appreciated! Thanks, Nitz

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Hi all . . . I've got a question that maybe you can help with - Got a 98 KTM 380 EXC that's running at full throttle at times when warmed up - (with throttle off - only way to stop it is with the clutch - kill button is useless when the RPM's are up there) Just finished putting this back together, so the maiden voyage has been maybe 1/2 mile, before it started to rev out of control! - I replaced the intake, reeds, both crank seals (flywheel & trans side) clutch, pretty much everything over the last year - (This thing is FULLY restored, & mint) - It's street legal, but I can't seem to get this over-revving thing figured out - Could it be a carb issue, or an air leak from somewhere? Also seems to smoke excessively, (running 50-1 mix) & won't run smooth at lower RPM's - Any advise would be MUCH appreciated! Thanks, Nitz

Have you tried taking it apart to see what is wrong??

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Air leak. Crank seals or base gasket. My guess would be crank seals if it is smoking excessively as well. Do a leakdown test to see were its leaking.

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Unless that thing is dieseling lol, the kill button should work at any revs

as above have you looked at your gear oil to see if its gone through the motor (smell it) should not stink of fuel

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I can tell you from personal experience, the killswitch does absolutely nothing on a 380 above about 1/4 throttle.

Check your throttle cable/slide action first. Then make sure your air filter, and airbox/carb boots are all sealed correctly. Then, leave it idling with the stator covered removed and spray some acetone behind the flywheel and see if it revs. If so, you have a crank seal leak. Repeate with the base gasket and the head gasket, or put some baby powder around both those junctions to look for leaks.

Btw, don't expect that 380 to run smooth at lower RPM's without a bit of head work and a leaner pilot jet. I ran a 35 pilot on mine at 2000-6000' after the RB mod. Best mod for the money.

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Crank seals are pretty easy to damage whEn you install them without oil. I would check there first. If you don't want to risk blowing up your engine, you can google how to make a leak down tester. It's pretty easy to do aside from hollowing out a spark plug. If you do get the engine sealed up and pressurized, you can use soap mixed with water in a spray bottle to find the leak. Just spray around the seal and base gasket and you'll find it right away.

Another alternative is that you're throttle is sticking. Lube the cable and make sure it isn't binding, and check visually to see that the slide is closing all the way until the stops.

Hope it helps,

Cal

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