Standard main jet#135

[Vmax4]

My Jetting Life

Well, here is my story. I run in the 2000 - 6000 elevation area. It is mostly 20 degrees F and warmer. I ran 135's all year with great success!!!

Now as you go up in elevation air gets less dense and you need to downsize jets. As air getts warmer you need to downsize jets also. I am correct in saying this??

Now with that said, I tried 132.5 MJ and found mine to be running so LEAN that there was no color on the plugs at all. That bothered me, cause in the service book, the elevation and temp I was in was calling for smaller jets. AND TO MAKE THINGS EVEN WORSE!!! I lost top end by moving down to the 132.5 MJ

So in reflection here, I think the 4 stroker likes it's gas, and is not particular to small changes. I think everyone running at sea level and cold should be finding more success with fattening it up a jet size. 4 Strokers are different than what most of us sled guess have been use to. Now to give some credit where credit is due, my brother "birdman" has helped me out in this area, so this info is from him also. Let me know what you guys think.

Thanks,
Steve

 

[grapeape]

How long did you run your sled before checking plugs?

 

[Vmax4]

Main Jetting

I ran them about 80-90 miles, and they showed nothing. I was mostly 1/2 to full throttle all day. The 135 jets made the plugs black, and I thought the studdering problem was that I was fouling plugs. turns out it was the steep terrain, and the updated float bowl solved the problem, THANKS TO THIS SITE. Anyway, about 80-90 miles and no color.

Thanks,
STeve

 

[tcsrx]

r1 bikes come with stock jetting at 130 mains

 

[Vmax4]

R1 Jetting

I would question the differences in air pressure on the motorcycle verses the sled. Also the air box is a bit different I would think. Who knows I am only guessing. Some one out there probably knows.

 

[snowbeast]

I can truly say when it gets warmer,i mean 30-40 above farenheight 137.5 to much even 135 r to use 132s but honestly,u can leave it along and be just fine,maines r not cheap if u buy yamaha,best way to improve milage drop needles.