Stroker Crankshaft?

I have a 2009 Wr250r and thought this might be a good mod, but wanted some opinions as to how this mod will affect the bikes reliability. I found a website with a +3mm crankshaft that brings it up to 263cc and uses the stock piston. Is this really a "Bolt in and go" mod or will I have to change other parts (cam, valves, etc..)?

I already changed the gearing but figured this crankshaft would add some low end grunt.

I don't do alot with 4 strokes but I think the cam would stay the same unless you want to put a more agressive one in there and give it more to brethe. The jetting will need to be changed for the same reasons as going overbore.

Since it's fuel injected i'd have to buy a programmer. The bike's rev limiter is at 10,800rpm so it has good mid to upper range power and likes to rev. Not sure if it would need a more aggressive cam.

DR. You only need to re-jet if going over bore, not stroke because you are not changing the piston surface area. You may have to adjust the fuel screw some.

To do the stroker, it is a bolt in, but you have to split the cases to accomplish it. I have experience doing strokers (not the YZ or WR) and its old hand for me, but i've done it before. With that said, doing an over bore cylinder is much simplier and quicker and less involved for the same gain. Buddy of mine did a 262 bore and his runs like a 450. I've got a 262 bore kit to go into mine and looking forward to it.

To me, if you go stroker on this motor, you are negating the design of the motor. Its designed to be a short stroke quick revving engine, and increasing the stroke will slow down the response, all be it only slightly and probably imperceptably.

Do the free mods, change the muffler out, get a JD jet kit, then come back to me. I really like the way my 04 runs now.

I thought it was the X that was fuel injected, not the offroad version.

The X has road tires and R has on/off road tires, both fuel injected. Most people that put a pipe on notice more mid and upper rpm power, not much low end improvement for the money spent.

Sounds like a big bore is a cheaper option but not sure about the reliability.

Figured a stroker crank would be more reliable. I think that adding 3mm to the crank would be less stress on the motor than a big bore kit. Sounds labor intensive to put in a stroker crank but if no other mods need to be done this might be an option.

Anyone else have experience changing a crankshaft?

I thought it was the X that was fuel injected, not the offroad version.

The off-road dirtbike based on the YZ is the F. The R and X are the street legal 250s, the R is the dual-sport and the X is the supermoto version. The R/X engine is different from the YZ/WR250F.

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