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2001 WR250F big bore refit

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Hi,

The above bike is suffering low compression and hard starting when cold... about to check the valves... just wondering when fitting a 290 kit to a fairly stock bike ( has an after market pipe) what also needs to be looked at changed or can you bolt straight on !!!

Benny

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The kits are just bolt on and go. Should change the timing chain while you're in there as cheap insurance. Hard to start cold is usually tight valves. Your bike being and 01 you might want to look into changing the exhaust cam to an 03+ so you can have auto decompression.

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I wouldn't recomend going to the Athena 290 kit on your bike without upgrading to a '03 or later crankshaft.

The '01 and '02 YZ and WR 250F's had a smaller crankpin that '03 and later bikes. Yamaha went to a larger crank pin in '03 to address reliability issues with the early cranks. Going to a big bore may put your 10-year-old-crank over the edge and cost you a lot of money.

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Oh, btw, if you do upgrade the crank, you would have to use an '03 or later YZ crank. The '03 WR crank was changed on the left side to accomidate electric starting and will not work on your machine. You would aso have the option of using the Hot Cranks stroker YZ crank and getting 306cc with the Athena 290 kit.

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Thanks for the info guys...i checked the valves and the inlet i could not get .05 mm under them so they are probably stuffed. Might just get new rings and a valve overhaul for the old girl and leave it at that.

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I just did a complete crank assembly and bearings, '03 auto de comp cam and new timing chain with the bolt on Athena 290 kit and tonight was the first ride........Awesome! Even starting while hot is easy as can be. The power delivery is very noticeable all through the range. It was the best investment to breath new life into my 2001 WR. I live in Northern Michigan and the rebuild has put a huge smile on my face. Good luck. Money well spent I tell ya

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