YZ250H

[VMX Andrew]

Just had my YZ250G motor completely rebulit from top to bottom
but used the outer cases of a 250H with a six speed gearbox cause
the front sprocket cover holder was still in place and got em dirt cheap.
The H cases had the 4v3 prefix number on the outside but on the inside
it had the prefix number 3r4.

[Viper666]

The H cases had the 4v3 prefix number on the outside but on the inside
it had the prefix number 3r4.

As do many Yamaha parts.

I got a NOS YZ250/400 side cover for $35 coz it was advertised with its IT425 part number.

[Simo63]

So Whitey how have you gone with resolving Carl's detonation problem?  He rode my 250H on the weekend even though it was detonating like a bastard at full throttle ... just had to short shift and ride around the problem.

I must confess that I realised on the way home that the fuel I was using was regular unleaded and not premium.  I expect that will make a difference and hope the problems disappears altogether.  if not then I'll look into getting the head remachined.

Anyone know what volume (cc's) the head is standard and what is should be when relieved to stop detonation?