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2013 yz250f engine moding questions

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I have a 2013 yz250f and it's just lacking in the power department for me and I don't wanna spend the money on a 450. I just a ordered stage 2 hotcams for it and I was seeing what the preferred valves and springs were for it I've seen a lot of pro x but I was thinking kimblewhite valves

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Stay stock on the valves.  Yamaha uses TI for light weight which translates into higher revving.  The Stainless valves are heavier.  To control those valves, the springs have to be upgraded (added expense), you guessed it, to heavier pressure.  All that translates into more pressure on the valve train down stream... cam lobes, bearing surfaces, chain, sprockets....

 

You "pays your money and you makes your choice," but I would not and have not "upgraded" the valve train in any of my bikes for the above reasons.

 

Other guys can chime in on the 2013 bike, I don't own one.  But if I had to guess, I'd bet AIS removal, muffler, and jetting would cure any issues you have unless you are a heavier rider.  Even that, this bike will pull 200+ guys without problems.

Edited by ronbuell
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I didn't have time to look up the AIS data.

Backfire screen used to be on the air filter frame. I did not, would not, and do not recommend removal. There is no appreciable performance gain.

You can get the filters that have back fire protection built in. Twin Air makes one.

I still have the screen in my WR. It has the snorkel removed, AIS removed, a YZ pipe and the carb rejetted. Made a big difference.

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Sell it ... buy the '14.

I had a 09 ( motor basically the same as 13) and now have a 14. The 14 smokes the old motor but it is still a 250F. I do think the 14 stomps the 13 in the 250F motor world but in no way does it compete with my 350 or a 450. I suggest you figure out if you only need a little more power or a lot more power. If you need a lot, sell your 250F and buy a used 450 if you don't want to spend the money on new. Or try to find a nice 250 2 stroke. Lighter and cheaper than a 450 but more power than your 250F.

Edited by motojunkiedan

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