crf 450 motor

[scottsworld]

what are the best year crf450 motors and why

[stocktires]

I'd go with anything but an 02' personally, but even those motors are pretty good.
The newer the better, but I believe the 05 and ups mount a hair different, don't quote me on that though.

[protrax]

02 is the same exact engine as an 03 . In fact the 02 has more valve lift and duration then 03 . The big difference is 03 has a better CDI
Any CRF engine is a awsome powerplant
Good Luck!

[stocktires]

There's quite a few other differences if remember correctly when rebuilding mine. You may know more than I do though.
Wasn't the piston different, more compression in the 03'? The crank was different as well was it not? I just remember alot being updated after their first year.

[400exMO]

I believe the 04 was when the compression was bumped. Really the newest, best maintained 450 is the way to go.

I bought an 03, had to rebuild the water pump and the head. Those are things you'll probably run into on any year.

[protrax]

Originally posted by stocktires
There's quite a few other differences if remember correctly when rebuilding mine. You may know more than I do though.
Wasn't the piston different, more compression in the 03'? The crank was different as well was it not? I just remember alot being updated after their first year.

Yes you are correct 02 comp was 11.5:1 03 comp was 12.5:1
The cranks are the same though . I was just assuming the engine was going to be built and would think everyone stopped using the 02 piston as soon as 03 were available . Definitelly no flaws either way , tear it down and build it for your purpose , if your running a stock bore stock 03 piston is great , You can run it on pump gas and pulls like a train

[stocktires]

I agree, any 450 will be more power than most can use on a track anyway.

[Rootar]

go for an 05 or newer the harness, cdi, coil, and stator were all improved, the mounts are diffent on the front but thats easily fixed. plus when you buy anything older than a couple years there is no telling how hard its been beat on espically the tranny and other stuff such as the water pump and little things will usally need repalced also.

[400exMO]

Originally posted by Rootar
go for an 05 or newer the harness, cdi, coil, and stator were all improved, the mounts are diffent on the front but thats easily fixed. plus when you buy anything older than a couple years there is no telling how hard its been beat on espically the tranny and other stuff such as the water pump and little things will usally need repalced also.

How far off are the front mounts on the 05+ crfs?? I have an 03 JB frame, sometime down the line I was gonna get a newer crf engine and build it up. How would I have to modify it for the older front horns?

[deathman53]

the bottom motor mount on 04+ is wider, I don't believe it uses the spacer that 02/03's did. If yours uses that spacer, your good to go, if it doesn't, you'll need the bottom mount moved wider. My lsr frame is just wide enough to fit the 03 motor, frames from 04+ probably can accept a 04+ motor.