426 to 450

[Michaelcrf450r2002]

Hey I have a 426 and completely tore up the motor I am in news of a whole new top end and want to convert it to a 450 so my question is why exactly does everyone say I can't put an 03 to 05 450 cylinder and head on the 02 426 cases any help would be appreciated. Thanks

[four-twenty-sixer]

From my understanding of it the head will not fit a 426 cylinder and a 450 cylinder will not fit the 426 case.

[four-twenty-sixer]

Look up Marv02, he built a 452 or 3 out of a 426.

[grayracer513]

The 450 cylinder head will not bolt onto a 426, but as I recall, you can actually install the 450 head and cylinder together on the 426.  Then, you have to ask yourself why you would do that.  The 426 and 450 have the same bore size, so the engine will still be a 426 unless you change the stroke.

 

Way too much money to put into a 426 when you could just go buy an older 450 for under 2K.

[Michaelcrf450r2002]

I know it's way too much money but I already put a lot of money in the rest if the bike so I'm at a catch 22

[grayracer513]

Yes, but the 450 top end won't get you what you want.  Even if it works, it will still be a 426 unless you step up to a new crankshaft.  All that for 24cc? 

[jojo1224]

Yes, but the 450 top end won't get you what you want.  Even if it works, it will still be a 426 unless you step up to a new crankshaft.  All that for 24cc? 

If 450 parts will fit the possibilities are endless, there are so many big bore and stroker combinations available. Who is gonna step up and try fitting a  450 crank, cylinder and head with 426 cases? Id love to try it if someone donates some used parts, I have a 426 to try it in and tons of spare parts to experiment with.

Edited October 4, 2013 by jojo1224

[four-twenty-sixer]

If 450 parts will fit the possibilities are endless, there are so many big bore and stroker combinations available. Who is gonna step up and try fitting a 450 crank, cylinder and head with 426 cases? Id love to try it if someone donates some used parts, I have a 426 to try it in and tons of spare parts to experiment with.

I do to now that i can no longer ride, so it looks like it might be tinker time.

[jojo1224]

I found this just by doing a quick google search.

this cylinder is very different . it will bolt down to the block but you will not be able to put your 6mm bolt in the bottom. the stroke of the two motors are different by 3mm and the 426 engine is a physically larger engine. we built one engine for a houser chassis built for a 426. we used a 450 bike crank cylinder and head left the little bolt out and built custom gear for the counter balance but i dont think you could use the cylinder without the head and with the bores being the same there would be no gain. hope this helps .

From here: http://www.atvriders.com/vbb/printthread.php?s=adb7ffe622906958eb5d81df5eb33580&threadid=384789

[four-twenty-sixer]

That's interesting, I wonder what the difference is in the counter balancer on the 426 to 450. Anybody know?

[rangerclass7sx]

posible or not, keep it stock why cause additional headaches to the problem

[four-twenty-sixer]

Stock is fine but i can't ride and I'll be really bored so i might be able to ride by the time i get done, or i might just take my buddy up on buying his 06 for cheap.

[Michaelcrf450r2002]

Thanks for all the ideas guys. I am probably going to go ahead and buy a 450 head and cylinder rather than 426 pieces the prices are the same for used parts on eBay so

[four-twenty-sixer]

Let us know how it works out.

[jojo1224]

Well I guess its time to start on my 426 - 450 hybrid. Broke the connecting rod today in my yz426f at about 10k rpm in 5th. Took out valves, cylinder, piston, cases and crank. Had about 25 hrs runtime on a complete rebuild. Versah rod broke broke at the small end, must be a manufacturing defect because you can see where it has been slowly cracking.