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matte30is
03-20-2009, 11:08 PM
Hi guys I have a 250x that I just got done rebuilding with a high compression piston. The motor used to be stroked out to 350cc but I took that crank out to return it more to stock specs so my wife could ride it. The previous owner ran 14/33 sprockets on it and with the motor being back to 250cc the gearing seems a little to tall.

What would be an ideal ratio? Stock is 13/39 so could I get a 36 tooth and keep the 14 and gain some pep?

thanks,

Matt
jason85atc250r
03-23-2009, 02:43 PM
want to sell the crank?
matte30is
03-23-2009, 04:33 PM
sure but the rod takes a weird piston pin size. Its a 20mm wrist pin. I couldnt find a piston to fit it. The only piston I found that uses a 20mm pin is a 400ex and well that wouldnt work. I still have the piston and pin but the piston skirts are cheesed.

Let me know if you want pics.
jason85atc250r
03-23-2009, 05:05 PM
the motor was probably from one off the major motor biulders like Tc racing of four stroke tech. they would have custom pistons made for there really big motors.

post up some pics of it.

just letting you know 13/38 if stock on a 250x quad. if you are running 20" rear tires the 14 front will work with the 38 or 39 rear. i have 3 old 250x's and they all came with 38 rears.
matte30is
03-23-2009, 07:01 PM
http://i118.photobucket.com/albums/o111/matte30is/100_2180.jpg
http://i118.photobucket.com/albums/o111/matte30is/100_2181.jpg
http://i118.photobucket.com/albums/o111/matte30is/100_2183.jpg

Thats the piston and pin in the pic. The guy said it was built in california and thought the rings were bad because it started smoking. I took it apart and the exhaust valve rocker broke off and well you know the rest. lol The crank has some gouges on the bottom of the weights but dosent have any play at the rod and spins smooth.

Thats the head that was on it. A valve seat came out on the exhaust side and I couldnt find anyone around here to fix it. Its massively ported with bigger valves. The exhaust valves were trashed from the broken rocker beating the stems to death.

If you want it make me an offer its just sitting in a box in my garage.
matte30is
03-23-2009, 07:03 PM
oh and im running 18 inch tires, check my other post in here it shows the quad the crank came out of.