i have an 04 yfz and want more power. im looking at high copmression piston and 470/480 big bore kit. what is the diference in reliabilty, and is the mod worth it?

 

if i were you. do both the cam mod AND a high comp piston. now THAT will add some power [img]i/expressions/face-icon-small-smile.gif[/img]

 

True.
The big bore increases volume, but the compression supplies the pop! None of this will make a real big difference if the old cam won't let the engine breathe to take advantage of it. Performance is not a single part, but several working in concert.

 

I would go big bore or add some aftermarket cams. If you bump the compression up to high you will have to run race gas

 

Wouldnt you have to get a heavier duty clutch kit for it with all the added power, it would rip the stock one apart wouldnt it?

 

deffinatly go with the cam but why dont you just find a big bore kit that has a hi compression piston that way you get more compression and more cc's. Check out www.cycleworksracing.net. They have a 500cc big bore kit and i think it has i hi compression pistion that brings you up to 13:1 from the stock 10:5:1 and while your in the engine you should get the oversized valves too, that will give you another few hp too

 

both would be best... but in yur case, get a big bore kit. just my .02

 

stock compression is 12.5 to 1

 

Stock compression isnt 10.5:1 Holeshotz, and its not 12.5:1 either. It's 11.9:1 and always has been on the yfz.

 

If you go much past 11:1 compression, you are looking at Octane problems (just to be aware).