yz250f frame, yz250 motor?

Would it be possible and if so how difficult would it be to take one of the new generation yzf frames and put a yz250 two stroke motor it?

Ive only ever seen one and that was a demo bike for shows done by a custom builder which consisted of a 2007 motor in a 2010 yzf frame, he also had an 01 cr250 motor in a 2009 CRF frame, both were sick bikes... When I asked him about the Yz all he would tell me was that "it wasnt easy". He did say he had 76 hrs worth of labor time in the Yz and over 100 in the Cr which was his first mx conversion. He said both bikes were ridden by a pro test rider and the yz motor in the yzf frame handled quite poorly. He said he was going to be making chasis adjustments and once the bike was dialed in he would be auctioning it off to the highest bidder.

So if I had to guess it would be a rather difficult task for the average builder without specialized equip and resources to ease the process, not to mention A DEEP WALLET.

Im seriously cotemplating doing the 05+ frame swap on my 03 yz though but that doesnt seem to be an extremely difficult task in comparisson.

My project started out as an 04 CRF250 chassis and an 87 CR500 motor. After getting it running the kick mechanism messed up resulting in the right inner and outer case busting. Now I have a fresh 02 YZ250 motor in it and it's actually a little harder than the 500 in some aspects. The intake to airbox is the real bitch so I'm ending up with mostly aluminum duct and even found an aluminum expansion chamber that fits nicely. Not sure if I'll put the 500 motor back in as I have a Max Power 285 jug I can put on it, but this has a brand new 250 jug, milled head and a Rad Valve and should run strong. It should be running in a month or so. The alloy tank was necessary for the 500 to fit but the stock plastic will be fine for the 250.




You post that in the honda section yet?

Only when it had the 500 motor in it. I'm real gun shy of the 500 engine so I'm going to leave the YZ engine it it and sell the 500. I'm partial to YZs as I also have a nice 01 250 and a recently turned yellow 06 YZ125.


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