Help identifying 247cc cylinders

[Pravin]

Thanks Ed .. good thought .. keep looking for heads ..
Can this top end be installed on our rd350s?

Cheers
Pravin

[Pravin]

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.de%2Fulk%2Fitm%2F260944985178


Are these the ones ?

Cheers
Pravin

[EE]

Yeah those are the heads.  Yes RD250 and RD350 bottom ends are identical  accept early 73-75 250's had a different primary gear ratio meaning the crank gear and clutch basket gears but you can use either one. But Yamaha went to the "RD350" ratio on all the RDs, LCs and RDs after that.

[m in sc]

SUPPOSEDLY THE 250s had slightly shorter cyl studs as well. if so, i've never had it be an issue. just an fyi. no need to swap them.

[EE]

Good catch Mark, true.