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high comp. piston
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Posted by: 300_dude

I would like to install a high comp. piston on my 300ex I know the best thing would be a 400ex but in the meantime..... can anyone tell me maybe exactly what needs to be done as far as what size piston I need to buy. I do a lil bit of everything. trails, jump ramps ride around, and sometimes race. so there is an idea of what I do and maybe what size piston I need. should I stick with stock bore or is it that as soon as you upgrade your piston you have to change the bore? I have jet kit, aftermarket exhaust and header, aftermarket rev box, monster ignition coil, k&n filter air box lid off. any comments will be greatly appreciated

Posted by: 250X_project

The 250X and 300EX are great machines!
When you put in a new piston, you need to hone it to deglaze the bore and regain the cross-hatching. If after honing there is still scratches than you need to bore the cylinder. Stock bore for your engine is 74mm. Remember if you did not buy it new you have no idea of really telling if it is stock bore still. Measure (or have measured) to be sure. Good luck building.