yamahabuyer
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- srviper and apex
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Ok I talked with Allen yesterday, he said to use the red spring and set it at 3 and 6 to help bring the rpms up. I also pulled a washer from the base as I already pulled the one in the tip last year. That brought me up to 8700. I will leave it there and see how in reacts on a hard packed trail
You are leaving alot on table. Got to get it to 9000 rpm. Way better performance.
subaru2006
TY 4 Stroke Junkie
I have my secondary setup machined and have ulmers clutch kit to run the 8dn. I haven't rode it yet thanks to this awesome winter. With that said last year I put around 1000 on one 8j belt. What a mess. I've never seen a belt with that amount of dust. I could only do 85mph once. Then the clutches were brown and I was limited to 75-80 with a strong wind on my back. I even had to clean the primary so it could slide. I hope the setup I'm running will help.
Subaru2006
Subaru2006
yamahabuyer
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I know, I want to get some fresh gas in it and get it on a hard trail vs the slush I tested in. If it's still to low I will pull another washer from the base to bring it up some more. Just need to do more testing once I get up to Michigan.
It really should not matter if slush,hardpack or ice. Just trying to save you time. Have fun in MI! Should be awesome.
It will. Just may have to fine tune a little.
subaru2006
TY 4 Stroke Junkie
Yup my problem is I have never tuned a sleds clutch before. And my first trip out will be in the UP and I won't be adjusting anything then. Hope its setup good enough I can worry next year and not have to mess with it this year. That way I can get a better understanding on clutch tuning.
Subaru2006
Subaru2006
Last edited:
superb
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When you run the four washers on the base of the weight, do you run 4 on one side of the weight or two per side. Thanks.
kviper
VIP Member
Just looked at some Dyno sheet's on the Viper. Coming out at 8,700 should be fine with it gaining to 9,000 on the big end for best MPH. Peak Torque is at 8,000 and holds past 8,500. Coming out of the hole in peak Torque and revving in to peak HP is usually where you wan't to be with these four strokes. It will also help keep you away from the rev limiter on hole shot. Every four stroke Yamaha
I've had has pulled more RPM on hard pack, the harder the better!
Two each side.
Kviper I agree but I am not seeing that as long as the distance is far enough always end up at 9160 any condition I have found. Speed is only thing that changes.
Studroes144
TY 4 Stroke God
Gotta jump in and give a bit of advice, I don't know how the weights from Allen's kit are setup or how you adjust them but the clutching theory is all the same, one thing that you shouldn't do is adjust your secondary spring wrap to alter your engine rpm, yes you can wrap the secondary spring tighter and it'll raise rpm, but the reason that's happening is because it's slowly the shifting process of the clutches which ultimately makes you slower everywhere. If you're buying a clutch kit from a vendor and your rpm is either too low or too high, adjust the weights accordingly. Again I don't know the weight profile of the setups being used here but on my kit last year it was very crucial not to load the heel of the weights at all, if the sled cannot pull 8800+ rpm right of the line when u wack the throttle you need to start taking weight out of the weights, the viper needs to be running as close to the rev limiter as possible to be at it's best performance. And one thing to remember, even when you have no weight in the heel of the weights and you have weight in the tips, that is controlling the rpm at launch somewhat because of the centrifugal force. If it were me I'd set the secondary at 6 and 1 or 6 and 2 and adjust accordingly on the weights the get it to rev 9000 rpm, just remember it's gotta rev up as quick as possible and hitting the rev limiter once or twice on a launch is not a bad thing, that method has proven to be the fastest setup we've seen when using a radar gun with actual speeds and times, if we lugged it along in the rpm it was always slower, let the engine scream.
STAIN
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I am pretty adamant about cleaning my clutches. I have never noticed any " burnouts " on the faces or an excess of belt dust. I run a variety of trails from low speed twistys to high speed stretch's, railroad beds etc. . I did try an 8DN a couple of times last year and found no performance gain. I am not saying it doesn't work for some but I don't believe it is a cure all. I think proper clutch tuning and elimination of binding is most important.
Good. Just have yet to see any 8jp running clutches that didn't show obvious signs of slipping. None. Take a pic.
kviper
VIP Member
You may be right but I would sooner see him low and work up than on the rev limiter for a weekend and not be able to make changes.
I also do not believe 8dn is a cure all. Never said that. Is best compromise I have tried so far. Intend trying 8dn equivalent in a ultimate and gates. I believe over long term the 8dn will wear clutch faces. Ultimax does not.
