265 mm dimensions

[R-Crazy]

I just picked up my 250 3 weeks ago. its bored to a 265, or so the guy says, he says he running stock head gasket, but only using one layer, and says he using a wiseco piston. Im pretty sure 265 id a .80 overbore, but wiseco only sells pistons in a .75 over bore assuming the stock bore size is 66mm for the 250. I think i can use a stock gasket too. Clue me in here. Im wondering if i should get a stock jug on ebay and then do my own work, but i wanna get a ESR 265 PV soon anyway. Tell me what i need to get for a top end rebuild, and anything else. thanx

dave

[R-Crazy]

bump

dave

[methyman]

First of all you need to get a stock gasket cut for your 250r. The bore on a 265 is 68.5 mm. Tha stock head gasket is about 66.5 mm. Do the math, too small. Wiseco makes pistons up to .140 over which is a 273cc motor for a 85-86 cylinder and .80 over for 87-89 cylinder. If it is running good I would leave it alone since you plan on getting a power valve cylinder. Also the head needs to rechambered when the bore size increases.


Later


Matthew

[airheadedduner]

One layer, he is probly using a cut CR headgasket. I tried milling a stock gasket to get it to fit a 295 cylinder and couldn't get it to stop leaking, I don't know if I did something wrong or because of the pleated gasket you can't mill it, I am not sure though. I think cometic makes head gaskets for the 265 overbore but I havn't had the best of luck with cometic gaskets. What kind of cranking compression are you getting right now. It sounds like you best bet to me is to run a cut CR gasket if the compression would be okay for it.

Pro-X also offers pistons for the 265 overbore. I would be more tempted to run a cast piston as opposed to forged to get the most life out of that sleave. But thats JMO:)