sleeve question

[kc7314]

my 426 is ruined so can the same sleeve be bored to 440 range? there is roughly 4mm thickness left at top of sleeve and there is still an o-ring at bottom of cylinder.

[igmif]

Sure you could bore it to 4mm over, and your engine might run 15 more minutes. You really have to get it resleeved. A 426 bore was already pushing the end of the sleeve's limit.

[underpowered]

stock sleeve.....NO. if is a re-sleeved 426 then yes it should be able to go to a 440 but no way if it is on the stocker.

[kc7314]

How do I know if it is not the stock sleeve? measurements or marks.

Or would I be better off putting my CRF450R motor on the ex frame?

[guinness77]

How did your 426 get ruined?

[kc7314]

let someone borrow it & they locked it up
- broke all 4 valves, 3 stuck in piston 1 shoved in head
- decent hole through piston
- sleeve has galling all the way down in piston travel
- rocker arms started to get eat up (I dont think from this)from cam being Web

[underpowered]

how much material is left at the bottom of the sleeve? a 426 on a stock sleeve should be getting thin, on an aftermarket sleeve there should be plenty of room for improvement. also is the sleeve into the bolt holes at teh top? a 440 sleeve will most likely slightly protrude into these holes.

[kc7314]

I guess the sleeve is stock because it is on the thin side on the bottom, close on holes up top but not in them. plus it is bent down low so a re-sleeve has to be done to do right.

would it be more reliable to go back 426 or bump to 440?
It ran like a scalded dog the way it is setup right now and don't want to change that unless it gets better w/440.