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okay guys, did a lot of testing today and you won't believe the results!
trails open today and are flat as a pancake and hard as a rock. set up the timers and went with stock clutching first.
the stock belt was sleeping so bad I couldn't get more than 76 mph in 660 ft. And only 86mph for a top speed.
Changed the belt as the clutches looked black from slipping. New belt and saw 88-89mph. With a top speed of 91mph
Went home, changed to my clutching and got 93mph top.
Ok, changed to 8dn belt and saw 91mph 660ft. And get this....top speed of 102mph. Rpm's were down so i went back and lightened the tip of the stock weights with a helix change to 47/40. Top speed 105.1! GPS don't lie
the 8DN works
here's the real shocker, because I took the newest 8 dn belt off of the nytro, I put the Viper belt on the Nitro and had to take the washers out. what's crazy is now the nytro is quicker and faster with the viper belt!!! 114mph on the dream meter!!!! Don't believe me nytro owners? Try it, i didn't believe it myself till i rode it. Temperatures are cool and the sleds are rockin! Win win win!
trails open today and are flat as a pancake and hard as a rock. set up the timers and went with stock clutching first.
the stock belt was sleeping so bad I couldn't get more than 76 mph in 660 ft. And only 86mph for a top speed.
Changed the belt as the clutches looked black from slipping. New belt and saw 88-89mph. With a top speed of 91mph
Went home, changed to my clutching and got 93mph top.
Ok, changed to 8dn belt and saw 91mph 660ft. And get this....top speed of 102mph. Rpm's were down so i went back and lightened the tip of the stock weights with a helix change to 47/40. Top speed 105.1! GPS don't lie
the 8DN works
here's the real shocker, because I took the newest 8 dn belt off of the nytro, I put the Viper belt on the Nitro and had to take the washers out. what's crazy is now the nytro is quicker and faster with the viper belt!!! 114mph on the dream meter!!!! Don't believe me nytro owners? Try it, i didn't believe it myself till i rode it. Temperatures are cool and the sleds are rockin! Win win win!
YamahaTim
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That's crazy! But good job, thanks. I sold my Nytro so I didn't have the chance to do that. But I know it worked using the 8DN belt for the viper!
09nytro
TY 4 Stroke God
Hey just shits and giggles do you have a 89L , that one is really close to 8jp I wonder how that one would work , been thinking about giving that one a try , it's so close in size I wonder why Yamaha didn't put this one on ....
Well I'm glad to hear about your results !
One more thing : does anybody know who makes the viper belt for Yamaha dayco,mitsuboshi , who
Well I'm glad to hear about your results !
One more thing : does anybody know who makes the viper belt for Yamaha dayco,mitsuboshi , who
YamahaTim
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09nytro said:Hey just shits and giggles do you have a 89L , that one is really close to 8jp I wonder how that one would work , been thinking about giving that one a try , it's so close in size I wonder why Yamaha didn't put this one on ....
Well I'm glad to hear about your results !
One more thing : does anybody know who makes the viper belt for Yamaha dayco,mitsuboshi , who
No I don't, but the Dayco one is that the extreme one? Cause I have two of them also. Are they just as good or better that the 8DN?
stingray719
TY 4 Stroke God
I lightened the primary weights and put on the Dayco 40G4340 (8DN equivalent) and took a short spin down the street with the wheels on and I cannot wait to try it on the snow tomorrow! Results to follow tomorrow night.
Oh, I cut 8fs down to 60 grams (I ride at around 10k)
Oh, I cut 8fs down to 60 grams (I ride at around 10k)
YamahaTim
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Right on... Let me know... I won't be riding tomorrow. 
No worries though, I'll have mine soon!
No worries though, I'll have mine soon!
RXVIPER
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That's awesome , bought new 8DN, will be putting it on today. Yesterday got 97 mph in 1000ft at a local radar run. Awesome track but real windy.
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Talked to familyman and cannondale27 last night about belts and i think a little shorter belt will do better, but whoever makes the Viper belt is slipping way too much.
still going to try some different secondary Springs and helix's.
still going to try some different secondary Springs and helix's.
09nytro
TY 4 Stroke God
NOS-PRO said:
Not that it matters but I would really like to know who makes the belt for the viper !
I was looking at the 89L but I don't think it will take the hp and torque of this engine as it was made for lower hp sleds that Yamaha had ....
DeerHuntr
TY 4 Stroke Guru
Well guys as you may or may not know I have been having a over reving problem, I ping the Rev limiter on the bottom from a dead stop then it grabs and pulls basically 8800-9000 and will slowly climb on top end from there. I had 1 ragged out old pos 8dn left in the garage from my Nytro so I cut the cord hanging out of the side of it and put it in my bag yesterday. A buddy of mine fouled a plug about 20 miles into the ride on his Rush so I figured what the hell and I put it on. I still hit the Rev limiter on the bottom end but not nearly as bad and the rpms pretty much stay 88-8900 after it grabs, saw 95 again and it was by no means done rpms were at 8950 on that pull.
It feels much more snappy and really responsive now. I put 110 miles on that old pos belt yesterday and I didn't think I would get 50. Pretty impressed it pulls really hard once traction is gained. I am going to get a clutch kit at some point from Ulmer most likely , will Ulmer set it up for the 8dn? Oh yeah, put in 1mm shims for my deflection on the stock belt already, the 8dn seems to be pretty good with that, never actually measured it however. Going out today. Pleased, will be buying a new 8dn this week .
It feels much more snappy and really responsive now. I put 110 miles on that old pos belt yesterday and I didn't think I would get 50. Pretty impressed it pulls really hard once traction is gained. I am going to get a clutch kit at some point from Ulmer most likely , will Ulmer set it up for the 8dn? Oh yeah, put in 1mm shims for my deflection on the stock belt already, the 8dn seems to be pretty good with that, never actually measured it however. Going out today. Pleased, will be buying a new 8dn this week .
YamahaTim
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Right on that's awesome! I'm happy it's fixing peoples lil problems.
monker
TY 4 Stroke Guru
Ran the 8dn today for 70 miles. Conditions were quite different from last weekend, so it was difficult to make a good comparison. Overall the sled seemed more consistant. Still pulling 8900 to 9000, but not getting in to the rev limiter nearly as much. Engagement felt good. Clutching is still stock for now.
RXVIPER
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Well Yamaha Tim and Nos Pro, put on the new 8DN and wow what a difference. The most I ever got out of the sled was 99 mph now with the new belt I've hit 101 mph. Had a hard time to get to 99 and now hit 101 mph with ease. Never had a Yamaha belt sit low in the secondary before I knew something was wrong with the belt and now everything has become perfectly clear the Viper has the wrong belt in it. Running with that belt makes the sled better to drive. Only had time to put on about 50 km on that belt so far but the sled feels awesome and pulls so much stronger. Definitely made a big difference on my sled. Thanks again guys for all your research 
sk-rx1
TY 4 Stroke Guru
Yamaha made a point at the Viper release that the new belt would be made by the same company as the 8DN. Mitsuboshi I believe. Of course things do change, with the AC thing and all. It be interesting if someone could measure hardness of both with a durometer.
YamahaTim
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Rxviper said:Well Yamaha Tim and Nos Pro, put on the new 8DN and wow what a difference. The most I ever got out of the sled was 99 mph now with the new belt I've hit 101 mph. Had a hard time to get to 99 and now hit 101 mph with ease. Never had a Yamaha belt sit low in the secondary before I knew something was wrong with the belt and now everything has become perfectly clear the Viper has the wrong belt in it. Running with that belt makes the sled better to drive. Only had time to put on about 50 km on that belt so far but the sled feels awesome and pulls so much stronger. Definitely made a big difference on my sled. Thanks again guys for all your research
No worries!
I just think it's cool at her people like yourself are trying it to good success! I think that's cool!
should last longer also 
