03yz450f motor for a 03 wr450f-will it work

My buddy blew up his motor on his 03 wr 450 f and we found an 03 yz 450 f motor for sale for much less than what we guess the rebuild will be. Will it work? I know the differences are the cams and gears but will it bolts up and plug in, also any carb issues?

I have a 03 WR450 and used to have a 04YZ450. The engine should bolt up just fine;however the clutch cable and where it mounts on the engine is different. As far as the carb;it dosen't have the air cut valve like the WR does--I would recommend using the WR carb on the YZ motor(with jetting adjustments). I am not sure if the CDI boxes are the same--may want to use the WR one. What kind of damage does the blown up WR motor have?

looks like the rod is threw both cases in the front, so rod,piston, both side crankcase and who knows what else, it is not torn down yet. I would think it would be a $1000-$1500 bill to have it fixed. We have a good dealer who's hourly rate is $50 but the parts are gonna hurt. Do you have any thoughts?

If it was my bike this is what I would do:remove engine from bike---teardown the engine to the cases (remove valve cover,cylinder head, and cylinder). After these parts are removed you could make a better assumption of how much the repair cost would be. Depending on how bad the cylinder is it could possibly be repaired--or you could do a big bore kit:thumbsup:

Here is a big bore kit for a 450 (which includes cylinder,piston,i would guess rings also,and gaskets for $630 http://www.dtdyno.com/shop/motocross/athena/

That makes sense, but if he could get this motor for $700 I think that would be the way to go assuming it bolts up and works with the gearing the only difference.

The 4 speed tranny sucks dicks. The gears from the WR will swap into the YZ engine cases (for these model years listed) though and if you look in the YZF forum you will see the parts list and instructions on how to swap them out.


I'd buy the YZF engine and swap out the gears from the blown motor.

All things YZF..


The only problem is that is an old engine as well and you might need to freshen it up as well.

Good luck.

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