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Is this unreliable?

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Hi I own a 2010 crf 250r and i want more power out of it, my decision was not to put a big bore kit in it because ive heard they are unreliable. I was wondering if i had a mechanic put in bigger cams and port the head. I was also wondering how much this is?

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The big bore is not unreliable if done right. There are a privateers running big bores in the lites class without issues. You need to have the crank ballanced with the bigger piston.

If you do a big bore you allso really need to do the head, cam and valve springs as well. Just bolting on an Athena 280 or a cylinder works kit makes more torgue and hp but they are really flat without the head work.

A stock bore crf250 with a good head is much better than the big bore with stock head and cam. Try the head work, cam and springs first if you need more add the big bore and ballance the crank.

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