Yamaha Jetting Recommendations

[Flatlander78]

I was wondering if anybody has had bad results with yamaha's jetting recomendations listed in the factory service manuals. In your experience, are they typically on the rich side, lean side, or right on. I talking on a completely stock engine obviously. The reason I ask, is I bought a 01 Mountain Max 700 and was told it had the factory jetting. I have ridden about 350 miles around my home area (2200 ft elevation) and it didn't seem to run to bad. Plugs looked good. We'll I took the carbs off to clean them and rejet to my elevation here since we are a little higher then what the factory jetting is and I am also installing an ATACC. What I found was 132.5 main jets (8000-10000 elevation according to yamaha), #55 PJ, needles on #2, and the air screw two turns out. According to that I should have been really lean with that jetting at my altitude. Wouldn't this be noticable on the plugs or shouldn't I notice something in the engine? I don't really know what to make of this. I can't believe I didn't melt a piston. Any thoughts???

 

[theultrarider]

My exwife had an 01 mmax 700. I want to say I was running even leaner mains than that here at 0-3000'. I will try to see if I can find my notes. But that said, yes yami like Polaris and most others are way too conservative in their jetting reccomendations. They don't won't to have folks burning them them down. If I remember right, the guys that were adding slp tripple pipes on thme around here were running the jetting that they came with for the stock single and they were still too fat!

 

[Flatlander78]

ttt

 

[PowderTrax]

Jetting

Look at your spark plugs, piston wash to get to know exactly how your're running. Lean down with main jets, drop you needles, change out pilots if you can.

All sleds jetting charts are listed to rich IMO. My old AC ZRT 800mc show 450 for main jets and I ran 400's around home and leaned down the noozles with smaller ones. In the mountains I ran 360's thru winter and 340's in spring. The one year I forgot to change out the 340's and for my first ride we were in Valemont (December) and my sled rocked!! I was a little lean leaving the parking lot but up top at elevation it was great, just had to be careful not to race too hard to the trucks at end of day.

My modded MNT Viper runs great... just did a ride on saturday and it got to +12C and we were riding near home @ about 1800-2000ft. She ran rich and could of rejetted as the ATTAC system didnt compensate enough due to settings for colder conditions.

 

[sledmaniak]

136,136, and 137.5on pto side works good on all stock at 6000 ft. I am pretty new to the 700 so i dont have a clue about the pilots or the needle settings.