RM370 Piston

[JohnnyO]

You can bolt the 400C barrel onto the 370 but if someone see's the 400cc writen on the cylinder you won't be able to race it in pre '78.
The 370 cylinder will bore to 400 no problem, i've done it on mine because it's easier to source std 400 pistons than o/s 370 pistons.

[oldyzman]

Just buy a yz400D....

[Toolboy]

Is the 400 piston 1.0 oversize???

Oldyzman.... I havent noticed the yz400D as they are usually behind me... hahaha

Cheers

Tim

[Doc]

Tim, you would be hypothetically looking at a 3.0mm oversize 370 piston to get to the std 400 bore. An overbore radius of 1.50mm which equates to 3.00mm when measuring the diameter.

[Toolboy]

Thanks Doc, so is there plenty of meat on the barrel to go out to this speck if required???

Tim

[JohnnyO]

Thanks Doc, so is there plenty of meat on the barrel to go out to this speck if required???

Tim

Yes.. like i said earlier my 370 is bored to 400cc using a std 400 piston

[Toolboy]

Johnny O...did you change the jetting to help keep the piston cool???

Thanks
Tim