mod-it
Member
Trying to help a guy with above sled, he's overturning his rpm's at 9100. Rides at 7000'-8000'. Stock clutches, I've heard they over-rev pretty bad with stock set-up. It has 10.3mm inner hole, empty outer. What's a good starting point to get this thing down to 8500 rpm? Oh, he's running a can on it also.
A K MtnViper
New member
2003 Mtn Viper set up.
Here is what I'm running. I ride at 8,500 to 11,000 with this set up and get about 8-9 MPG. I'm a hair lean at 8,500 and a hair rich at 10,500. Carb heaters off.
PTO 145, CENTER 147.5, MAG 147.5, Pilots 45, Needles 2.0, Air screws 1 7/8.
Torsion spring silver, Torsion cam 43 degrees, 90 degree twist on secondary.
13.3 steel outer rivet, 13.3 Alum inner, 8DN 10 weights, Green-White-Green spring
I engage at 4,050 rpm and max out at 9,100 out of the hole and settles to 9,000
21 x 40 gearing. I'm jetted for 20 to 0 degrees air temp. If its colder out I my sled runs a little lean, warmer is richer of course. On deep powder hill climbs I can hold about 45 mph track speed. I know the MPG sounds low, butttt most my riding is off trail in untracked powder.
Keep in mind that with SLP pipes you want to run at 9,000 rpm ish and he is going to be 30 less hp or so. Hope this helps.
Here is what I'm running. I ride at 8,500 to 11,000 with this set up and get about 8-9 MPG. I'm a hair lean at 8,500 and a hair rich at 10,500. Carb heaters off.
PTO 145, CENTER 147.5, MAG 147.5, Pilots 45, Needles 2.0, Air screws 1 7/8.
Torsion spring silver, Torsion cam 43 degrees, 90 degree twist on secondary.
13.3 steel outer rivet, 13.3 Alum inner, 8DN 10 weights, Green-White-Green spring
I engage at 4,050 rpm and max out at 9,100 out of the hole and settles to 9,000
21 x 40 gearing. I'm jetted for 20 to 0 degrees air temp. If its colder out I my sled runs a little lean, warmer is richer of course. On deep powder hill climbs I can hold about 45 mph track speed. I know the MPG sounds low, butttt most my riding is off trail in untracked powder.
Keep in mind that with SLP pipes you want to run at 9,000 rpm ish and he is going to be 30 less hp or so. Hope this helps.
Last edited:
add some tip weight! start with the 13.3 in the tip, adjust from there. too much rpm, add weight, not enough, lighten up.
mod-it
Member
I was hoping someone would speak up with what is working in their stock Mnt. Viper so that he could start out really close to 8500rpm. Thanks for the input but we know what to do, just trying to get a close starting point.
At what altitude is he riding? Here are the Yamaha clutching spec's from the Mt. Viper book:
8000-10000 ft. 13.3mm steel in none out
6000-8500 ft. 13.3mm steel in 10.3mm out
4000-6500 ft. 13.9mm steel in 13.3 steel out
Primary Spring G-W-G
Secondary Spring G twist @ 70 degree
21/40 gear 8 tooth drivers = 2.14 rati0
Engagement r/min = approx. 3900
Shift r/min = approx. 8400
8000-10000 ft. 13.3mm steel in none out
6000-8500 ft. 13.3mm steel in 10.3mm out
4000-6500 ft. 13.9mm steel in 13.3 steel out
Primary Spring G-W-G
Secondary Spring G twist @ 70 degree
21/40 gear 8 tooth drivers = 2.14 rati0
Engagement r/min = approx. 3900
Shift r/min = approx. 8400
mod-it
Member
Thank you, that's what I'm looking for.