Did the YFZ your rode with the 13:1 piston seem to have any more power than yours. Mine should be in this week and I am hoping for some power gain after ripping it all apart.

 

With full mods (pipe/AB/timing) adding the pistion made it feel much snappier. The dyno chart showed a 1 to 2 Hp gain from 5400 rpm to 9000 rpm. But it felt much more then that (seat of the pants). Riding in any gear at 1/4-1/2 throttle, you can just blip the throttle and it just roars.

PS IM 4wheelfun at BT.

Let me/us know what you think, You wont be dissapointed.

 

Well I called my dealer today and he says the pistons are still 2 weeks out so I called a yamaha dealer back east and they had 1 piston in stock. They said they ordered it 3 months ago and they next day aired it to me so I will have it tomorrow. I will post results tomorrow night (late) when I get it done. DO you know if they had to jet it up much to run the 13:1 piston. Also what pilot jet are you running in yours.

 

Your dealer is on drugs.

Anyway we are running stock pilot, 165 main, GYT-R needle 4th position. Runs great, Actually I just got word Kory is out at Glen helen right now testing the piston in his race bike. Reports are he is Loving it. He will be running it in the next GNC race.

 

Are they running 165 main with the 13:1 piston. I know you said they were just running pump gas, how is this working out. I live at 5000 ft so I do not think I will have a problem. I will probably kick it up 6 points with some klotz octane booster.

 

Yes the 165 with the 13:1, on pump gas. That was at 3000'. We did not need to change it from where it was at without it. Whatever jetting you are running now will probably be just fine.

 

Thanks for all your help. This forum is pretty cool.