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KX 250 Compression?

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I have a 2003 KX 250. Recently the compression has gotten real hard to kick over. It wasnt this way before, I took out the plug and it kicks over freely. I thought it might be starting to sieze or lock up. It will start and run good, just really high compression. Any ideas would help out a lot thanks!

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I have a 2003 KX 250. Recently the compression has gotten real hard to kick over. It wasnt this way before, I took out the plug and it kicks over freely. I thought it might be starting to sieze or lock up. It will start and run good, just really high compression. Any ideas would help out a lot thanks!
If the compression is going up, there must be a lot of deposits inside the combustion chamber.

You could also be losing a wrist pin bearing or rod bearing. They can seem to move freely when no pressure is applied (no plug means no compression to push against the bearings) but be binding when they are under pressure. This isn't very likely, but it is possible.

Time to pull the top-end for an inspection.

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I figure out that my power vavle was all gummed up with in burnt oil. I cleaned it up. Seems to be working better. I run 32-1, seems like I have lot of oil. Is that normal or should it be buring off.

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I got my bike back together and it didnt seem to fix my problem. The exhaust valve is working smoother, but its still has really high compression. When the plug is out it kicks over easy. Any ideas where i should look next.

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Put a gauge on it and see what it really is, maybe before the power stuck open and now it's working correctly and your now normal. Just a thought.

Ed

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ya Im not sure the exact compression but its def higher than normal, It doesnt have a smooth kick either. I know these are hard to kick, but it us to have that smooth kick all the way through. Feels like im gonna break the kick lever and it will miss a couple stokes. I can get it started. and it runs pretty good. Seems to be smoking alot more tho. But its hard to tell with this bike and the cold/ being a two stroke

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If harder than what seems normal or what used to be, Chokey is right. You really need to get in there and check things out. You could have a blown ring which binds with the plug in because when you add to resistance, it's gets really bad. I know ours is hard as hell to kick but it also has a bit more compression that a stock motor.

If you don't have one, go to any auto parts store & for about $30, get a compression tester. If not sure how to use it on a 2 stroke, post up and we'll help ya out.

Good compression is 180-210psi. Anything below 145-150, it's due a topend.

Also, sending a PM.

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On page 6-10 of the service manual for the 250, there is the governor shaft. I believe it operates the KIP Valve. Im not sure the operation of the governor shaft. When i kick over the bike should that rod be moving so the kip exhaust valve is opening and closing? When i do kick it over nothing happens with that lever. I doesn't move, Before i take the cover off and look whats up just wanted to see if anyone knows the normal operation of it.

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Stays in (closed) until the motor gets to around 4500rpm then it moves out to open the PV so what you are seeing is normal.

Ed

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On page 6-10 of the service manual for the 250, there is the governor shaft. I believe it operates the KIP Valve. Im not sure the operation of the governor shaft. When i kick over the bike should that rod be moving so the kip exhaust valve is opening and closing? When i do kick it over nothing happens with that lever. I doesn't move, Before i take the cover off and look whats up just wanted to see if anyone knows the normal operation of it.

You won't be able to kick it over fast enough for it to move.

Stop playing with it and take it apart :busted:

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I took a compression reading and it is around 225/230PSI. The manual says 185, but i did it when it was cold, carb off but the reeds were in, and the exhaust was off. Is this high? i read that some peoples were around 210psi.

My bike is pretty much stock besides, some jetting, exhaust and a air filter

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WAYYYYYY too high. Something is wrong somewhere. Even with ours having an aftermarket head with a smaller chamber, it was never that high. You have issues somewhere. Chokey may be right about the smallend bearing or somewhere in that area.

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how can a bad bearing affect compression. i can see how it can affect it its hard to kick over, but the compression should still be the same right? If it was around 185psi and it hard to kick then i would assume the bearing binding/siezing up. it sounds like the exhaust is not coming out, its almost making a thumping noise. I guess i'll have to look into that.

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how can a bad bearing affect compression. i can see how it can affect it its hard to kick over, but the compression should still be the same right? If it was around 185psi and it hard to kick then i would assume the bearing binding/siezing up. it sounds like the exhaust is not coming out, its almost making a thumping noise. I guess i'll have to look into that.

The bearing "could" or "can" cause a problem, not we are sure 100% that's you problem. It "could" be any number of things causing you to have this problem of yours but, in till you take the time to tear in to the bike your never going to know what the problem is......:busted:

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You said it was smoking maybe your sucking trans oil in thru the crank seal, which would decrease the volume available in the crankcase for fuel mixture raising the compression and making it smoke more as it burns the excess oil.

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