Trying The 8DN BELT

[cannondale27]

My results vs a 300mi 8jp

Much more consistent rpm at all speed and throttle
Lost 200 rpm on top
No grey coating on clutches

Ideally I would like a belt with the same compound as 8dn and length of 8 jp but as long as this 8dn lasts as long as previous 8dn I will work with it. I agree it should act like lower gearing but it does not. Just the opposite in fact. I think the stock 8jp is slipping a lot and it in fact feels lower because of that. I will clutch back the 200rpm and put some miles on.

 

[YamahaTim]

My results vs a 300mi 8jp

Much more consistent rpm at all speed and throttle
Lost 200 rpm on top
No grey coating on clutches

Ideally I would like a belt with the same compound as 8dn and length of 8 jp but as long as this 8dn lasts as long as previous 8dn I will work with it. I agree it should act like lower gearing but it does not. Just the opposite in fact. I think the stock 8jp is slipping a lot and it in fact feels lower because of that. I will clutch back the 200rpm and put some miles on.

Sounds good! Let me know!

 

[bleedyamaha]

8dn

Well I just picked up a 8dn 17641-01 belt from a friend who has Nytros. Already broke in. Stopped at Yamaha and picked up shims. Part no 90201-061H1 Hope this is the right combo. Will find out this weekend. Not sure if I like my gates belt rpms were all over but I was riding rivers so not sure what was slipping. Rev limiter still popping at bottom end. More testing and tuning to come. Enjoying the sh__ out of this machine and always fun to make it even better.

 

[YamahaTim]

Re: 8dn

Well I just picked up a 8dn 17641-01 belt from a friend who has Nytros. Already broke in. Stopped at Yamaha and picked up shims. Part no 90201-061H1 Hope this is the right combo. Will find out this weekend. Not sure if I like my gates belt rpms were all over but I was riding rivers so not sure what was slipping. Rev limiter still popping at bottom end. More testing and tuning to come. Enjoying the sh__ out of this machine and always fun to make it even better.

There should already be one shim(washer) in there. Just add one more for all three. So two total and that should be good.

 

[kritter5150]

I am thinking about re-shiming my secondary and trying a 8dn again with my secondary wrapped to 6/2 just to see if I still bump the limiter like I did with the 8jp. At 6/1 wrap it all but cured my Rev limiter issue but I still hit it occasionally but it feels like I lost some midrange vs my 6/2 setting. Both are much better than my stock settings my machine came with. The argument that the little longer length of the 8dn is gearing the machine down is correct I think but I don't see the problem with that. There is no way a stock Viper is going to pull itself out of gear anyway, aren't they geared for 115 or so?

Mine was exploding the 8JP. 4 times. Different clutching and it still did. Went to stock yamaha parts and still exploded. Shimmed changed belt to 8 DN and same clutching and no issues. I'm ok with losing a little top speed to have a belt last for more than 300 miles!! And a 100 dollars a piece. I need a better clutch kit now to take max advantage of my belt. I am waiting for Allen at Ulmer to get me going. He is testing. I see on the trail 106mph and to me that's just fine! I'm not a big lake racer. I will do it for the fun of it, but I won't set my sled up for it. No reason. I want to get from one corner to the next fast and without exploding a belt!!

my thoughts exactly. i tried the 8 dn with shims. and it lasted 150 miles. looks like it rode up to high on the primary and eventually over. im going back to the 8 jp for now. but i m getting tired of having issues. im sure they can handle 190 hp

 

[YamahaTim]

I am thinking about re-shiming my secondary and trying a 8dn again with my secondary wrapped to 6/2 just to see if I still bump the limiter like I did with the 8jp. At 6/1 wrap it all but cured my Rev limiter issue but I still hit it occasionally but it feels like I lost some midrange vs my 6/2 setting. Both are much better than my stock settings my machine came with. The argument that the little longer length of the 8dn is gearing the machine down is correct I think but I don't see the problem with that. There is no way a stock Viper is going to pull itself out of gear anyway, aren't they geared for 115 or so?

Mine was exploding the 8JP. 4 times. Different clutching and it still did. Went to stock yamaha parts and still exploded. Shimmed changed belt to 8 DN and same clutching and no issues. I'm ok with losing a little top speed to have a belt last for more than 300 miles!! And a 100 dollars a piece. I need a better clutch kit now to take max advantage of my belt. I am waiting for Allen at Ulmer to get me going. He is testing. I see on the trail 106mph and to me that's just fine! I'm not a big lake racer. I will do it for the fun of it, but I won't set my sled up for it. No reason. I want to get from one corner to the next fast and without exploding a belt!!

my thoughts exactly. i tried the 8 dn with shims. and it lasted 150 miles. looks like it rode up to high on the primary and eventually over. im going back to the 8 jp for now. but i m getting tired of having issues. im sure they can handle 190 hp

See that's what I don't get. Yamadog has the 8JP with his turbo and it seems fine. And mine I went through four. Now with the 8DN it's holding together. Weird. Oh well it works so I'm sticking with it. Doesn't make any sense!

 

[kritter5150]

I am thinking about re-shiming my secondary and trying a 8dn again with my secondary wrapped to 6/2 just to see if I still bump the limiter like I did with the 8jp. At 6/1 wrap it all but cured my Rev limiter issue but I still hit it occasionally but it feels like I lost some midrange vs my 6/2 setting. Both are much better than my stock settings my machine came with. The argument that the little longer length of the 8dn is gearing the machine down is correct I think but I don't see the problem with that. There is no way a stock Viper is going to pull itself out of gear anyway, aren't they geared for 115 or so?

Mine was exploding the 8JP. 4 times. Different clutching and it still did. Went to stock yamaha parts and still exploded. Shimmed changed belt to 8 DN and same clutching and no issues. I'm ok with losing a little top speed to have a belt last for more than 300 miles!! And a 100 dollars a piece. I need a better clutch kit now to take max advantage of my belt. I am waiting for Allen at Ulmer to get me going. He is testing. I see on the trail 106mph and to me that's just fine! I'm not a big lake racer. I will do it for the fun of it, but I won't set my sled up for it. No reason. I want to get from one corner to the next fast and without exploding a belt!!

my thoughts exactly. i tried the 8 dn with shims. and it lasted 150 miles. looks like it rode up to high on the primary and eventually over. im going back to the 8 jp for now. but i m getting tired of having issues. im sure they can handle 190 hp

See that's what I don't get. Yamadog has the 8JP with his turbo and it seems fine. And mine I went through four. Now with the 8DN it's holding together. Weird. Oh well it works so I'm sticking with it. Doesn't make any sense!

weird? yes. annoying? absolutely. with my 8dn i was seeing 8800-9000 rpms. now with switching back to 8jp. i wonder what my revs are going to be

 

[YamahaTim]

I am thinking about re-shiming my secondary and trying a 8dn again with my secondary wrapped to 6/2 just to see if I still bump the limiter like I did with the 8jp. At 6/1 wrap it all but cured my Rev limiter issue but I still hit it occasionally but it feels like I lost some midrange vs my 6/2 setting. Both are much better than my stock settings my machine came with. The argument that the little longer length of the 8dn is gearing the machine down is correct I think but I don't see the problem with that. There is no way a stock Viper is going to pull itself out of gear anyway, aren't they geared for 115 or so?

Mine was exploding the 8JP. 4 times. Different clutching and it still did. Went to stock yamaha parts and still exploded. Shimmed changed belt to 8 DN and same clutching and no issues. I'm ok with losing a little top speed to have a belt last for more than 300 miles!! And a 100 dollars a piece. I need a better clutch kit now to take max advantage of my belt. I am waiting for Allen at Ulmer to get me going. He is testing. I see on the trail 106mph and to me that's just fine! I'm not a big lake racer. I will do it for the fun of it, but I won't set my sled up for it. No reason. I want to get from one corner to the next fast and without exploding a belt!!

my thoughts exactly. i tried the 8 dn with shims. and it lasted 150 miles. looks like it rode up to high on the primary and eventually over. im going back to the 8 jp for now. but i m getting tired of having issues. im sure they can handle 190 hp

See that's what I don't get. Yamadog has the 8JP with his turbo and it seems fine. And mine I went through four. Now with the 8DN it's holding together. Weird. Oh well it works so I'm sticking with it. Doesn't make any sense!

weird? yes. annoying? absolutely. with my 8dn i was seeing 8800-9000 rpms. now with switching back to 8jp. i wonder what my revs are going to be

Probably all over

 

[BETHEVIPER]

Has anyone changed the center to center to be correct?
Just making the secondary narrower to take up the extra length is not going to fix everything. If the belt is longer, and you make it ride up on the secondary further, this means, it will bottom out the primary first, making the sled slower overall. The other thing running a belt long for the center to center is you are gearing the sled down, so I have no doubt that the sled pulls better, even if the rpms are off. We are talking about 4-6mm different center to center depending on belt variation between the two belts. That is alot when dealing with clutching.
I wish I had one of these sled here and time to fix it. The belt may work better but not without a correct center to center or overdrive in the primary to get back what the lower gear ratio and the clutch bottoming out took away from your gain in a better quality belt. Not to mention, when you lower the gear ratio(make the secondary larger diameter) your changing the effect of the helix and spring on that belt. This changes how the primary will react to these new loads.

To really put this theory to the test, assemble your clutches with no springs, use a warm belt(bends easier) around your clutches, you can tell somewhat close, how your belt will be when the clutches shift out. I say close because under load, the primary will get closer.

can someone measure center to center and see if they can loosen the motor up and how close they can come to the correct distance of 268.5?

Sorry if I seem ranty, I just think many are missing an important piece of this pie. If I am wrong, great, that just means I have learned something.

Someone donate me a viper

When I checked my center to center it's at 263mm ( posted about 10 pages back )
And you are not ranty at all , I must say you hit the nail on top of the head but I will also say you will not get it though some of these guys heads ......

only 5mm difference, cant effect anything

check out the mounts to see if there is a way to get it correct,

 

[09nytro]

I don't think it's adjustable , I was looking at that when I was trying to get the 8nd to work

 

[09nytro]

I also had 3 1mm washers on each bolt , and my belt deflection was at 1 1/2" , I like it at 1" if possible !

 

[YamahaTim]

I also had 3 1mm washers on each bolt , and my belt deflection was at 1 1/2" , I like it at 1" if possible !

Wish it worked for ya! Don't know why it don't??

 

[09nytro]

Oh I will figure it out , but I is going to take some machining of the clutches and the right helix , weights and springs combo , just not sure if it's worth it or not !

Schmidt bros have my primary clutch and a couple helix doing some machining for me , that will give me more top end with the stock belt .....

 

[YamahaTim]

Oh I will figure it out , but I is going to take some machining of the clutches and the right helix , weights and springs combo , just not sure if it's worth it or not !

Schmidt bros have my primary clutch and a couple helix doing some machining for me , that will give me more top end with the stock belt .....

Right on, I have bought a lot of stuff there...for my RTX SE Nytro before I smashed it.

 

[09nytro]

I'm 45min from them , Chris is a good guy and there shop is awesome !!