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98 yz 250 cutting out at top speed

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I just bought this bike about a week ago and every time I pin it in 5th gear she dies about 20 seconds after doing so. When it cuts out, it dies completely, can't jump it or kick it over for about 5-10 minutes. It only happens in 5th. Engine was rebuilt about 8 hours ago (top and bottem end), compression is fine. Just had everything serviced, including fresh oil and coolent. Seems to hesitate a little bit in 1st and 2nd but it isn't to bad. I was reading around, and i've got 2 ideas as to what it could be, either overheating or a bad cdi box. I can't see it overheating, as I am riding in weather thats almost 0C (or 32F), and the cdi box was replaced about a year ago. Any idea as to why this is happening? When I try to kick it over right after it dies, there is little to no effort to kick it over. I have to wait a bit of time for it to be able to kick over again. Once it kicks over, she is perfect.

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by whom? You or the seller?

Seller. But the seller was good friends with a co worker of mine, and the person who rebuilt the engine is a reputable guy in town. Has great compression and doesn't have any knocks. I had brought it into my small engine mechanic for a complete look over, and the only thing he found that could be off is a bit of gunk on the power valve which he cleaned up.

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I would be testing the cdi and the coil per the manual with a description like that.

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I got a cdi and coil on order. Think it may be a bad seal somewhere? Where the engine when revving very high loses compression and thats why I can't start it for 5-10 minutes?

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Sounds like the coil is the issue. Try that before you install the CDI, you may be able to save yourself some money by returning it.

Edited by BDubb106

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My 98 was doing the same thing when I got it turned out to be a broken bottom ring .

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Thanks for the help guys. I'll update the tread when I pin point the problem for future reference. I'll start with the coil, then cdi, then clean the carb, then open the engine if all those fail.

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