A little viper clutching diagnosis needed

D

dbutler1988

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Joined
Mar 23, 2014
Messages
27
Location
Northern Maine
I had the shop put some on some speedwerx pipes, jet, and add clutching that came with it (all used but excellent condition). Went for a ride and runs great but a little bit of an issue with the clutching.

It shifts to peak RPM (9000) at about 3/4 throttle and I can get to about 95mph. If I go WOT it drops to 8500 and actually stops accelerating and even slows just a bit.

Clutching is:

Silver secondary
8 ek's with 3.6 and 4.6g
YWY primary
51/45 helix

Any ideas?
 
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first off the sec spring... silver, too stiff for snow with a button clutch. Thats a spring thats good for grass racing. It will cause what your describing because its too stiff and makes the rear clutch want to backshift while your front clutch is trying to upshift, so they fight each other and it doesnt gain rpm or mph like you describe. I would use a green sec spring at 70 for snow.

The rear helix really wouldnt be my choce to run a sled at 9000rpm on snow, but it will do for now, try the new sec spring it will help quite a bit. but before we talk about the helix, describe to me what your riding is like and what your going to do with this sled 90% of the time you ride it.
 
Thanks a lot Mrviper, I really appreciate your help. I will locate a green secondary today and try that out at 70 twist. My riding is 90% trails. Twisty woods that come out into 1/2 mile straights. I like to see what it can do in the straights.

I know an old racer a couple miles away that has a few Helixs lying around that he said I could try. I don't have the angles yet, but I'll go look today.
 
Did a bit of testing today:

Put in green spring with 70 twist and it pulled to 9000 but dropped off even further to 8000 and would creep slowly back toward 8400. Pretty dead on top.

Referred to some literature from SLP (similar pipes). They called for 47 straight helix and red spring at 70. Figured I'd give it a try.
With this it would hold significantly longer at 9000 than the other 2 setups, drop back to 8500 and creep to 8700.

Each time it pulled like an animal to 80mph, but when it pushed back to 8500 it killed the acceleration/top end.

I'm running similar top ends to when the sled was stock. Seems like it gets there in half the time and just falls on its face.

Thoughts?
 
helix is too steep on the finish angle for the engine to pull peak, the rear clutch is torq sensing so when you get up top the engine doesnt make as much torq so the rear clutch tries to backshift.

what angles does this guy you know have for helixs? what would work well is somthing around a 49-50 start and 40-42 finish angle since you have a 4.5 rivet in the tip of the primary weights, it will want to keep pulling upstairs then. see what helix that guy has to test with.
 
The helixs he gave me today were 56/44, 43/39, and 45 straight.

I'm currently running the 47 straight with red spring at 70.


Other available parts:

Purple secondary
Pink secondary (maybe faded red?)
Green secondary
Stock Secondary
Stock weights
51/45 helix
 
put in the 43/39 with the viper stock red dot sec spring at 70-80 twist see how it does, that should pull alot better up topend.
 
The results from today:

Added 43/39 with red sec spring at 70. Pulls 9000, but closer to WOT then drops just briefly and gains quickly back to 8700. Is not flat on top any longer,but still 300 rpm shy of where I should be. Any thoughts on how to get to 9000 and keep everything else the same?

It doesn't bite as hard down low right now, but it's a trade off for not falling on its face up top. I'm totally fine with that because I'm not studded so it was just spinning everywhere last night. Just want to get closer to 9000 on top.
 
put the red spring at 80. You can go up to 90 degrees with a red, after that youll want to use the green dot and start at 60-70 as its a stiffer spring, but I think youll find the red will give you better mph. The reason it doesnt feel so mean at first is the 43 start on the helix, I suggested you start with that one because it had the lowest finish angle. Like i said before really what your gonna want is about a 49-50 start angle and 40 finish angle. My go to helix for a piped viper is a 50/40!
once you get it real close with that guys helix you can buy your own and know what size to get. You also may just taking a tad bit of weight off the tip of the clutch weights, like .5 gram and run 4 grams in the tip instead of 4.5 that will help on top rpm.
 
I played with the twist and it didn't help much.

After a weekend of toying around I brought it to a different shop. This time it came back with the pipes all realigned and the hood closing correctly. This shop is an hour drive away and not as fancy and new, but I was impressed with their work compared to the colossal local dealership with the new building and "gold certified" yamaha techs....they didn't do a good job at all. The second shop changed the jetting completely and went through the airbox. They said it pulls and stays with the RPM it needs at the top. The owner said he had one set up as is personal sled and they put a lot of time into it getting it to work right. I will test it tomorrow. Regardless of how it runs I will play with the clutching again just to learn/test new things. The different setups you had me try taught me a lot, even though the issue was not totally related. They did say it was clutched pretty well as we left it. I'm anxious to test it and tweak it even more....now that its running correctly.
 
if everything is all good with your clutching now make sure to write it all down where its all set as that way if and when you go in to tinker with stuff you can always get back to where you started if you happen to slow it down...lol.... been there dun that!!!

glad to hear you got it fixed anyways.
 
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