yz400F vs yz426f

[ZRider400]

I recently picked up a 99 yz400f motor... Going to run it in a 250r chassis.

Wondering if any one has experiance swapping parts between the 400 and 426 motor. Im looking to possibly swap cylinders/pistons, and maybe get a cam that has auto decompression ( to eliminate the decomp cable).

Also this motor has 2 inlets on 1 pipe going into the water pump.... i dont know what is up with that, id imagine its from both radiators.(on the bike). Anyone try using the inlet pipe from a YFZ450 on these ? So that it re directs the hose away from the header.

[Slinky]

do you have the motor in the bike yet?

if not we need to look to see if one of those will fit in my chassis....i think i wanna drop a bigger motor in it since i dont think its going to sell.

[ss440ex]

here is an idea...
For the water pump.

[wishmasstir]

Originally posted by Slinky
do you have the motor in the bike yet?

if not we need to look to see if one of those will fit in my chassis....i think i wanna drop a bigger motor in it since i dont think its going to sell.

i think i might know someone selling a complete hybrid setup *wink wink*

Ive seen people use the yfz450 inlets, I had a yz400f bottom end with a 426 top end on it. I didnt convert it myself but i guess its just a bolt on ordeal. The yz450f cams can be used to get rid of the decompression cable also. The two inlets on the water pump are for both radiators though

[jrspawn]

Hey whats up. Both the 400 and 426 are very strong running engines. As for switching a 400 to the 426, its pretty straight forward. Just swap your cylinder/pitson and rings fromt he 426 over. Make sure you use the correct gaskets though and replace the timing chain while in there. And the yz450f cam is what you want for auto decomp. I normally dont run these though, i just run the stock cams most of the time and remove the decomp. mechanism. Once you learn the trick to starting these engines its not an issue! Hot or cold i can fire em up right away:D Not sure what you have for a carb, but id suggest running the 426 FCR carb. Some of the 400's were the older style carb setup. Feel free to get ahold of me with any questions you might have, ive got a good bit of exp. with these setups.

Thank you
Justin

YFZ450 inlets work. I used the yfz450 inlet for the top and the bottom one by the header I just cut right below where it goes into 2 and then just clamped the radiator hose over it and it worked fine.

[toobuzy4suicide]

I just had my 426 motor rebuild, now im ready to throw it back in, but the person who originally did the swap, didn't do a very clean job. He welded an aluminum flange on the head so you can run a small rubber hump hose to the carburator, then he glued the air filter joint to a piece of aluminum tubing that is pretty much a 90 degree angle prob because of fitment issues(dont know how air got thru but whatever)..Now i have a new head on the block, with new valves and a hot cams auto decomp exhaust cam, my question is can i run the factory clamps and connecting joints from the 426's head to carb, then run the 426 filter joint and clamps to a 250R intake tube and air box? and how do i delete the manual decomp lever?

[brian250racer]

I am pretty sure the connecting rod (small end) is a different size on the 426 motors.
I used the YZ450F cam on my hybrid and it worked great, but I ended up changing the cam chain 2-3 times a year due to the small difference in the tooth size between the two.

[ss440ex]

and how do i delete the manual decomp lever? [/B][/QUOTE]


Several companys sell a plug for the front R/H corner of the head.
It blocks the hole where the oem cable went to the head.
Its a aluminum plug with an O-Ring.

[hontrx265r]

you do have to do the connecting rod unless you run a bigbore 400 piston in the 426 cylinder.. but less reliable and harder to get the pistons