Viper RPM/POWER drop after 1/4 mile?

X

XRX1

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Nov 16, 2004
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31
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S.E. MINN.
I have a '03 Viper with 4000 miles on it a Dalton 53/41 helix, green spring at 70 deg. twist and the RPMs ran 8500 for about a 1/2 mile then creep up to 9000. So, this year I wanted to fix the problem and was told to add a 4.5 gram rivet to the inner weight hole, so I did. I finally was able to run the sled for the first time this year and the engine seems to take a while to get up the rpms, the people behind me can smell my belt as well. As my riding day went along I got to long stretches and the rpms went from 8500 to 7500 after a 1/8 mile run so I get off the gas , slow down, nail it again rpms go to 8500 then boggs down to 7500 and tops out at 65mph. Compression is about 110/120/120 mag. Is this a tired engine already, too much clutch weight, or a weak spark? Plugs look normal color.
 
Worn clutches in need of a rebuild, and glazed belt?

Secondary spring weak?

Dirty power valves?

Could be a lot of things.
 
Go back stock and start from their, vipers like to rev at 8700, i made many changes in my polaris cluthing and had to go back to stock and rethink all my clutching upgrades, what works for some may not work for you.
 
Make sure you have your secondary tightened the proper way(clockwise) If your belt is smokin it is slipping & you maybe put the secondary together the wrong way.
 
The spring is twisted clockwise, I also tried two different springs with same effect. Can this be the pinched cable problem I hear so much about on Vipers, creating a weak spark at high demand? Bad CDI?
 
Mine kind of did the same thing. Took the secondary apart and the helix bushing and movable sheave bushings were spent!! Cheap fix.
 
The bushings in the helix do look quite worn...maybe the problem? Powervalves were cleaned 800 or so miles ago, this is a major bog down after the engine gets to full speed for a brief time then a power loss and rpm drop to 7500. If I slow way down and hit it it will once again rev up to 8500, then back down to 7500 after 1/8 to 1/4 mile.
 
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