esr 330 cylinder question

[kiesta00]

I was looking at esr's website and noticed that the 310 and 330 big bore kits do not require case machining, but it says the 330 kit requires the use of a "long rod crank ('87-'89)" ...I thought the only difference b/w the 86 and 87 bottom ends was the rod length, not the crank? Why would I have to use an 87 crank with the 330?
Thanks

Keith

[250R-Dee]

All the of the OEM ATC/TRX 250R cranks have the same 72mm stroke.

330cc without case machining sounds kinda weird. I guess that setup uses a +5 stroker crank but it will still need a 74mm piston to get to 330cc.

[hang1p]

the reason is the sleeve wiil not fit into the base with out the cases being machined so esr cuts the sleeve enough so that the sleeve does not go into the cases and stops at the end of the spacer plate so you need a long rod to incorperate the spacer