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Wont start......New Problem

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OK, here's the deal.

I have about 45 races (harescrambles) on my 250F. The compression is getting pretty bad. I can barely feel it while kicking (slowly). It is getting to the point where I have to "drag" it to get it running. Once it is warm it is alot better, starts fine (like normal, one kick). Here's my theory: the rings are shot, the bike gets up to temp, then the rings expand and compression is returned, bike runs fine. If I'm missing anything, PLEASE, let me know.

I have tried everything (carb,cdi,decomp,cable,plug,ect...) and nothing helps. I have not changed anything (mechanically) on the bike in 6 or 7 races. Only std race prep.(clean filter,lube,check everything).

The bike has Vortex, and Dr.D, the rest of the bike is BONE STOCK. (yes, even the jetting and filter).

I have been having this problem for the last couple of races (three weeks). I have one race left this year (Budds Creek next Sunday). If we can get through this race then I can tear down and rebuild if I need to.

If you have ANY suggestions, PLEASE let me know.



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I tend to agree with your rings diagnosis after hearing what you have already done. There is one way to 100% verify your suspecion. remove the plug and put a teaspoon of "Marvel Mystery Oil" down the spark plug hole. Hold the compression release and slowly push the motor over. Then release the comp and if it is the rings the compression should return. If it doesn't you could have carbon buildup on one or more valve faces, causing a bad seal situation.

The Marvel Mystery oil will not harm your engine but you will need another plug after you clear the cylinder. I run 2 ounces per 5 gallons of race gas just to keep the upper end lubricated.

If it turns out that it is a worn set of rings, the worst that could happen is that an oil ring could collapse and turn your ride into a mosquito sprayer. At that point I'd call it a day. Wouldn't want to score a cylinder.

Good Luck...

Bonzai :)

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