426..Bigger Displacement Options/Questions

4 replies to this topic
  • racerx573

Posted January 12, 2006 - 08:17 PM


Was looking at going with a bigger displacement in my '01 426.. (quad chassis)
I have heard of issues with pistons cracking in the 440 & 444's. Anyone have any experience with this?
Was also looking into possibly using a YZ450 cylinder if it will bolt on, or maybe stroking it. (if a YZ450 crank would fit??).. or maybe even a YFZ450 ATV crank/cylinder..if that would also fit..

I was checking out the ice cube cylinders, and see they don't make one of their own for the 426, but they have some nasty kits for the 450's..

  • TeamScream

Posted January 13, 2006 - 12:06 AM


I have several thousand miles on a 444 kit in an 01 (WR426) core.
It was flawless when I tore it down 2 weeks ago.
The piston was starting to slap a little bit (noticeably) but I now know there is good reason for that.
The trick with a big bore is to run tighter than prescribed piston to wall clearance as long as you can keep the heat in check.
I had the cylinder honed to what wiseco then recomended for clearance (.003 in.) the new build is going together at .0012 in. (.030 mm) and aparently that is the magic number from my sources.
Falicon can stroke the stock 426 crank 2mm with no case mods required, and if you run a big bore (JE 97mm piston) you will end with a monster.
That is my next path.....it just sounds like too much fun not to do it.

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  • Pincushion

Posted January 13, 2006 - 09:53 AM


I've also got a 2mm bore on my 426 (=444cc's) w/ Wiseco 12.5:1. The motor certainly pulls harder from the bottom through the mid and the top feels about the same. It pulls my 14/47 gearing harder than it pulled 14/50 before the rebuild. I got the kit from Lukes Racing and have had no issues since I rebuilt it last summer.


Posted January 16, 2006 - 05:26 PM


i also want to step up to 444 on my '00. it just needs more power at the dunes(definately noticable this past weekend at glamis). would i be able to run a 13.5:1 oversized piston with the big bore? i want to keep the compression up to make as much power as possible. if so, would it run on pump gas? that is a big concern. thanks.

  • TeamScream

Posted January 16, 2006 - 05:42 PM


It will run on pump gas no problem, but with 13.5:1 compression getting the jetting spot on is more important.

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