Bored to 340.. (250r question)

[300excrazy98]

Hey guys, I am buying this 250r and the guy tells me that the cases were machined out by duncan racing for a 340 cylinder. my question is can you still run a stock cylinder? stock bore? or do you have to run the 340?

I dont know about the R but I like you sig, g unit haha

[300excrazy98]

ha thanks.. bump

[stocktires]

Yes, a stock cylinder is fine. You just now have the option of running a 340. I can't remember all the details of case machining because it's been so long since I had my R :(
For some reason I want to think there's a negative side effect to having the cases machined.

[300excrazy98]

thanks

[trx250rkid]

theres no negative side affect that i know of. you can run any cylinder you want.

[matt250r21]

The only thing I can think of is a very slight loss of crankcase pressure.

[C-LEIGH RACING]

Running a stock jug on cut out cases causes just a bit lower crankcase presure which will lower the top rev some but makes up for it with a bit better bottom end responce.
If your running a 38mm carb, you can over come the extra volume that the case cutting added by clamping on a 39/41.5mm carb, but then the power will be different, little sluggish on the bottom.
Neil

[Eddiesanders250]

can you have the cases machined without splitting them?

[C-LEIGH RACING]

Originally posted by Eddiesanders250
can you have the cases machined without splitting them?

No sir,

All the shavings & chips that the machining will produce from the cutting process will end up in the main & crank rod bearings, + the crank webs will be in the way of the machining tool bit.
Neil