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Brand new wr 290 jetting?

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I just bought my Dad a brand new 05 wr 250 and will be installing an athena 290 kit before the motor ever gets started. I will also be installing the yzf exhaust cam and doing all the free mods including removing the exhaust baffle or installing the yzf pipe. Is the #40 leak jet still the magic number because I will also be installing one of them? So what is a good baseline jetting for 70 to 80 degrees near sea level? I will be using the stock needle for now to get started with. Also is the air cut valve mod worth doing? Thanks.

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I just bought my Dad a brand new 05 wr 250 and will be installing an athena 290 kit before the motor ever gets started. .

Can't help you much with your questions.................but how do you feel about adopting a second Dad????:applause: :applause:

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Well, I finally got him on a Yamaha but it is going to cost me. I'm not covering the whole bill but I am covering the upgrades and I never have been one to be satisfied with a stock bike. He is 65 and this is his first 4-stroke. He has been riding KDX's for over 10 years now.

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Thanks for all the replies!

I don't know how the Yamaha getting is to start with (I suspect very close to perfect) but making the engine bigger is going to have the effect of making it very slightly richer at more air flow sipons gas more efficently. So put it together stock, go ride and after its broken in consider very slightly smaller jets

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Do a search under my username. I had a lot of problems getting mine dialed in. I have it close now, but can't recall off top of my head the exact jets, but pretty sure I posted it (I think on the WR/YZ 250F forum). I had to go a good bit leaner on the jets (I think 165 or 168 main).

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