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440ex2001
07-31-2004, 10:22 PM
I am thinking about doing this swap on my 2003ex. I hear the engines are pretty high what is about the average price on these engines. How much could I get out of a 440 engine with ported and polished head? Does this engine have DOHC and 5 valves? Am i even talking about the correct engine. I have seen this swap mentioned here and there and just want to see what needs to be done to my bike.
bradley300
07-31-2004, 10:27 PM
you are mentioning two different motors, the crf is a honda, and only comes in a 450. the 426 in a yamaha yz motor. the yamaha 426 is the cheaper of the two motors and is alo older
4wheelboy
07-31-2004, 11:56 PM
yes the crf is 450 the yzfis a 426

heres a jrd quad with a 426 motor:)


http://img.photobucket.com/albums/v305/mx300exshift/camms_jrd_hola.jpg
440ex2001
08-01-2004, 05:22 PM
which one is more easily and commonly swaped to a 400ex?
maxamillion
08-01-2004, 05:53 PM
i dont think one would be much easier than the other. u need to modify your frame or buy an aftermarket frame made specificly for a 426 or 450 motor. my friend has a yami 426 motor stroked to a 440 and wow this thing rips! i could hardly go past second gear on his track cuz i didnt need to. ive never got the chance to ride a crf450 quad tho.
440ex2001
08-01-2004, 06:43 PM
Does anyone know what needs to be done to fit a crf450 engine on a 400ex frame?
4wheelboy
08-01-2004, 06:56 PM
Originally posted by 440ex2001
Does anyone know what needs to be done to fit a crf450 engine on a 400ex frame?

make motor mounts, guesset it. make a mount for a radiator. make sure the sprockets line up. ect im pretty sure the crfs are faster:p
440ex2001
08-01-2004, 07:41 PM
thanks for the info, I was wondering if someone on the forum has done a swap like this before and had any info.
Florida400EX
08-02-2004, 03:26 PM
The yamaha will be the faster quad, but the honda will be more dependable, in my mind. The conversion isn't TOO hard to do if you have access to a machine shop, and a buddy who can help you with the machine work.

good luck!
TC426EX
08-02-2004, 03:55 PM
The CRF450 conversion will definitely be faster than a YZ426 or even 440 IMO. Ive ridden both conversions and like the CRF better personally. To me, the built CRF conversion bikes are a little faster than the built 450R's Ive ridden actually...
Florida400EX
08-02-2004, 10:21 PM
Originally posted by TC426EX
The CRF450 conversion will definitely be faster than a YZ426 or even 440 IMO. Ive ridden both conversions and like the CRF better personally. To me, the built CRF conversion bikes are a little faster than the built 450R's Ive ridden actually...

I'm assuming, you haven't rode a piped YFZ? basically the same thing as a yz450f conversion. It would kill a 450R, which is pretty much the same thing as the crf450.
Mxracer53
11-30-2004, 07:02 PM
I'm assuming, you haven't rode a piped YFZ? basically the same thing as a yz450f conversion. It would kill a 450R, which is pretty much the same thing as the crf450. Not even close ive ridden a 03 crf , a yfz with a gytr pipe,jet kit, and open lid, and k&n filter,and my 450r(mods in sig) and my 450 is faster than the yfz(my friends) and the crf(stock) is the same as my 450.
a crf and trx motor are totally different.
pnut420
11-30-2004, 07:16 PM
It could go on and on all day. Generally a YZ450 is going to be a faster motor than a stock CRF, depending on the type of riding. Now the 426 is down on CC's and didnt have the same head design or stroke etc.... as the newer 450's. I know someone on here that is a sponsored racer and had hhad both YZ and CRf's and the YX was a little faster, either way cant go wrong, as far as manitanane/reliability wise, both are pretty pumped up stock and need regular maintanance... Top end once a season, etc...
Narly R
12-01-2004, 09:35 PM
My crf feels a lot stronger/faster then our yfz ever could be! Revs out WAY faster. It has tons more low end. Pulls way harder.

In the 250r it is a problem cause the engine is so tall in the R frame, but they dont have that problem with the ex frames. Maybe try talking to John Arens. he was going to make me a killer deal, but i didnt do it.. long story. But I think he can hook you up with an aftermarket frame like that pretty cheap, if you go taht route. Just gotta do what 4wheelboy said.

I have a high compresion piston, and stage 2 cam in mine.... it goes pretty good to say the least...:cool: