bigbore

hi ive got an 06 rm250 and previous owner put a fmf pipe on it and i geared it 2 or 3 teeth less in back because i dont like shifting to often and ride dunes . im looking for alittle more power and was thinking about porting but im out of US and only quad porting is done here. so whats the best band for buck? is a bigbore kit the best thing to do and if so what company and cc is best? im looking just to get the same power as a slightly modded 450 (cams, pipe couple other small things). i ride about 80% dunes and 20% mx but might race mx and see how it goes.

i need to run pump 91 gas too. hows the reliability of bigbores? anything else would be a better option? or would a bigger piston and maybe something else give enough power?

thanks

Gday Duner,

I ride in the desert here in outback Australia and i can recommend a big bore for sand riding. I have a 285 kit for my 07 RM 250 and it hauls through the sand. Reliability has never been a problem with the correct jetting, and i also used AVgas 100 to keep the engine cooler in the heat and soft sand.

I am currently selling the cylinder and have it listed on Ebay if your interested.

Toolboy

Gday Duner,

I ride in the desert here in outback Australia and i can recommend a big bore for sand riding. I have a 285 kit for my 07 RM 250 and it hauls through the sand. Reliability has never been a problem with the correct jetting, and i also used AVgas 100 to keep the engine cooler in the heat and soft sand.

I am currently selling the cylinder and have it listed on Ebay if your interested.

Toolboy

seen your ad, 2.1 mm over is only a 265. what is the part # of the piston?

and i'm 99% sure it won't fit a 01-02. it might fit the 03.

Gday Don

I have a New Wiseco 743M06850, +2.10 mm over bore 68.50 mm bore.

What makes you say that the cylinder will not fit an 01 or 02 RM???

I know it will fit an 03 because of the cylinder stamping.

Toolboy

Gday Don

I have a New Wiseco 743M06850, +2.10 mm over bore 68.50 mm bore.

What makes you say that the cylinder will not fit an 01 or 02 RM???

I know it will fit an 03 because of the cylinder stamping.

Toolboy

that is the piston for a 99 rm 265. the rm265 03-07 's are using a yamaha piston. Wiseco# 804MO6850 and my 07 cylinder would not fit on my 01. i tried it.

the 275's are using a honda piston 526MO6950

here is a list

Big Bore 250 Piston and Gasket Kits in 265 and 275cc

Honda CR250 1986-91 265cc 614MO6850 $140

Honda CR250 1992-96 265, 614MO6850 $140

Honda CR250 1997-2001 265, 702MO6850 $140

Honda CR250 2002-04 265 801MO6850 $140

Honda CR250 2005-07 265 804MO6850 $155

Kawasaki KX250 1993-2003 265, 617MO6850 $140

Kawasaki KX500 1989-2001 525, 575MO8800 $150

Suzuki RM250 1990-95 265, 642MO6900 $140

Suzuki RM250 1996-98 265, 614MO6850 $140

Suzuki RM250 1999 265, 743MO6850 $140

Suzuki RM250 2000-02 265 756MO6850 $140

Suzuki RM250 2003-08 265 804MO6850 $155

Suzuki RM250 2003-08 275, 526MO6950 $140

Yamaha YZ250 1992-98 265, 677MO7000 $140

Yamaha YZ250 1999-2008 265, 804MO6850 $155

Yamaha YZ250 1999-2008 275, 526MO6950 $140

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