03 YZF450 Bottom end

does anyone know if the bottom ends on a 450 are the same as the 400/426? With the exception of 5 gears vice 4. Broken cases on bottom end.

Nope, the 450 cases are entirely different, and will not interchange. YZ400 cases will work, however.

So you are saying the 426 cases are different and I would be able to use a bottom end from a 98/99 400?

Yes, I believe that's exactly what I said. The cases are the same, but most of the internal parts are different.

then theoretically I should be able to bolt up my top end to a 400 bottom end and go?

What happen with my cases was were the kickstart shaft seats into the right case the whole back of it broke out. So I'm trying to do some research to see what my options are. Do you have any other helpfull info that I may need to do this swap?

I belive you will need the Crank assembly out of the 450 motor to keep it a 450. I was told that the rods are different lengths.

Nick

OK, wait a second. I think I see a problem here. The way you originally asked the question, it sounded like you were trying to repair a 426.

HOWEVER, if you have an '03-'05 YZ450, that's a whole different thing. The crankcases for those years will neither fit anything else, nor can they be replaced by anything else. The are unique.

Yes I have a 450. Thanks for the info.

What are the major differences of the cases for the 06-07 450's

versus the 05's. If an 05 case is cracked coul I use a 06.

thanks

What are the major differences of the cases for the 06-07 450's

versus the 05's. If an 05 case is cracked coul I use a 06.

thanks

The '06 case is again, entirely different, and won't interchange with earlier models.

The '06 has the oil reservoir built into the engine, a different cylinder angle, different ignition layout, internal top end oiling, and a wider transmission.

Didn't yamaha go to an aluminum frame in 06 or was it 07? I think they used different mounting points.

Didn't yamaha go to an aluminum frame in 06 or was it 07? I think they used different mounting points.
They did start the aluminum frame that year. The hard points are all in similar places, but may not match up. Either way, the crankcases won't interchange.

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