Trying The 8DN BELT

[larrypolaris]

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

I hear you.

Back in my grass drag days. I would have the dealer give me a half a dozen belts or so from behind the counter and I would measure everyone and buy the ones that were the correct length.

It's amazing how much belts vary. And especially aftermarket belts.
And how much belt length and compounds can affect performance.

We ran 600, 700, & 800cc Polaris's on the circuit.

I always ran OEM belts.

Belt length and c to c are key.

 

[stingray719]

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

you are not wrong, this is the problem exactly......
shimming the belt will do nothing after engagement. I guess some guys enjoy going slower in the end.
A properly shimmed, clutched 8jp works

I suppose you have never used different length belts for clutch and gearing tuning? Alot of us have.

Tell you what, find and post the length and more importantly the acceptable belt length limits as per too long or too short as belts vary from manufactoriing. Post results from 8Jp, 8DN-00 and 8DN-01 and then lets talk. I am not posting them as I already know the tolerances.

Or, call Ulmer and Hartman and tell them they are wrong and you are right either will do.

I must say I haven't , I tried it for the first time with this sled and it didn't work !

And I called Allen and Tom but they haven't got back to me yet , oh and I did talk to loan at thunder products and he just laughed !

Allen and Tom have always spoken to whomever calls them, I am losing faith in you being able to tell the truth.


.

 

[stingray719]

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,

Now that is the point, the belt lengths are so little difference....in fact the tolerances overlap on the belts. If you think gearing down less than 1 percent is noticeable I would be surprised.

 

[stingray719]

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

I hear you.

Back in my grass drag days. I would have the dealer give me a half a dozen belts or so from behind the counter and I would measure everyone and buy the ones that were the correct length.

It's amazing how much belts vary. And especially aftermarket belts.
And how much belt length and compounds can affect performance.

We ran 600, 700, & 800cc Polaris's on the circuit.

I always ran OEM belts.

Belt length and c to c are key.

YES that is what I said posts back, we used to use diff belt lengths for some minor tuning on race sleds. The tolerances allowed on belt manufactoring usually allow up to a half inch difference. So this gnashing of teeth from the 8DN being longer is actually amusing.

 

[stingray719]

One more post for my favorite Tecnical Wizard In Training aka TWIT.

Viper belt according to specs in Yamaha book is 44.17 inches or just a hair under 44 1/4 right? Check out these belt specs.

Part #: HPX5009
OEM Replacement : Yamaha 8DN-17641-00-00, Yamaha 8DN-17641-00, Yamaha 89L-17641-00, Dayco 138-4432, Carlisle 138-4432U4, Dayco HPX5009, Carlisle XS805, Gates 38X4420
Length: 44-32/64"
Width: 1-3/8"

CARLISLE ULTIMAX® Pro Drive Belt #138-4432U4
fits Yamaha OEM #8DN/89L-17641-00/01
Length = 45-1/4" ~ Width = 1-27/64"

Why the diff in the Ultimax belt?

Sept 2007 issue of SnowTech Page. 49 says:"

Pros: Yamaha belts are hard, Last forever...
Cons. Lots of Slipping, lost of acceleration, lots of heat

They Recommending the use of the Ultimax 3 #138-4432-U3 because:

its Softer, more grip, less slip, slighly longer,Ultimax that is softer and 1/4" longer, this enabling us to get the drive belt to the top of the Secondary Sheaves on the driven clutch. Dayco has a one year warranty. Buy "two" and you have a lifetime supply of belts. Read the back of the belt sleeve, less slipping is "Free Horsepower

So you can see 1/4 of an inch length on a belt or even a half inch isn't a big deal. Now for someone who you might believe, Ulmer Racing.



We are getting ALOT of calls and emails asking about running the old 8DN belt on the new SR Viper models.

Can it be done? Yes

Will your Ulmer Racing for the SR Viper clutch kit work with the 8DN belt? Yes, but the 8DN belt will likely drop your shift RPM slightly.



The only reason I once again post this is so misinformation from those not qualified to give it does not confuse those wanting factual information. And by that please don't think I am coming down on those asking questions....of course not! Just those that insist they are wrong when facts ay otherwise. After all we are here to share info and make our sleds better and sometimes it is hard to seperate good info from bad.

 

[09nytro]

You know what stingray and who ever else !
I'm not saying the belt won't work , all I'm saying is you have to get everything to match , it not just put the belt on and go and it going to work awesome because its not going to happen , you have to change your clutching and pos. the gearing .

A box of clutch parts and gears and a day or two maybe three of test and tune and it will work , but there are other options , that's all I'm saying !

And yes I have talked to Tom , great guy !

So bottom line is it's not just a put on and go thing , weight profile ect. All plays a part !

Have a great day !!!!!!

 

[MCApex44]

I am getting Only 90mph @9050 rpms with 8dn belt and Ulmer clutch kit on a pretty long run on the lake. So i am getting more top end mph with 8dn but now she is a pooch from a dead stop. From a dead stop my buds Stock 09 Nytro pulls me in mid range by two sled lengths and also has more mph on the top end. My old Nytro xtx would beat that same 09 Nytro everywhere. The wifes 2010 Vector is eating this Viper up also. I am really frustrated with this Viper right now. Mine seemed better with the 8jp and ulmer clutch kit where it was beating a 07 F8 by 4-5 sled lengths in 500ft from a dead stop. Rpms were about 8700/8800 but getting any top end mph was a struggle with 8jp. i would certainly like to stay with the 8dn belt and i hope Ulmers upgrade kit for the 8dn belt will provide the fix. The frustration is buying a $11,000+ sled and having to dick around with this thing and spend more money.

 

[stingray719]

I am getting Only 90mph @9050 rpms with 8dn belt and Ulmer clutch kit on a pretty long run on the lake. So i am getting more top end mph with 8dn but now she is a pooch from a dead stop. From a dead stop my buds Stock 09 Nytro pulls me in mid range by two sled lengths and also has more mph on the top end. My old Nytro xtx would beat that same 09 Nytro everywhere. The wifes 2010 Vector is eating this Viper up also. I am really frustrated with this Viper right now. Mine seemed better with the 8jp and ulmer clutch kit where it was beating a 07 F8 by 4-5 sled lengths in 500ft from a dead stop. Rpms were about 8700/8800 but getting any top end mph was a struggle with 8jp. i would certainly like to stay with the 8dn belt and i hope Ulmers upgrade kit for the 8dn belt will provide the fix. The frustration is buying a $11,000+ sled and having to dick around with this thing and spend more money.

Quick call to Ulmer seems in order. We had to unwind the secondary a bit as we were spinning the 153 Powerclaw we put on it on takeoff. Call Allen I am sure he knows what to do there.

 

[09nytro]

I am getting Only 90mph @9050 rpms with 8dn belt and Ulmer clutch kit on a pretty long run on the lake. So i am getting more top end mph with 8dn but now she is a pooch from a dead stop. From a dead stop my buds Stock 09 Nytro pulls me in mid range by two sled lengths and also has more mph on the top end. My old Nytro xtx would beat that same 09 Nytro everywhere. The wifes 2010 Vector is eating this Viper up also. I am really frustrated with this Viper right now. Mine seemed better with the 8jp and ulmer clutch kit where it was beating a 07 F8 by 4-5 sled lengths in 500ft from a dead stop. Rpms were about 8700/8800 but getting any top end mph was a struggle with 8jp. i would certainly like to stay with the 8dn belt and i hope Ulmers upgrade kit for the 8dn belt will provide the fix. The frustration is buying a $11,000+ sled and having to dick around with this thing and spend more money.

You will have to add more weight to the primary to get the rpm's down to 8800 and you should get your mph back!

 

[MCApex44]

I am getting Only 90mph @9050 rpms with 8dn belt and Ulmer clutch kit on a pretty long run on the lake. So i am getting more top end mph with 8dn but now she is a pooch from a dead stop. From a dead stop my buds Stock 09 Nytro pulls me in mid range by two sled lengths and also has more mph on the top end. My old Nytro xtx would beat that same 09 Nytro everywhere. The wifes 2010 Vector is eating this Viper up also. I am really frustrated with this Viper right now. Mine seemed better with the 8jp and ulmer clutch kit where it was beating a 07 F8 by 4-5 sled lengths in 500ft from a dead stop. Rpms were about 8700/8800 but getting any top end mph was a struggle with 8jp. i would certainly like to stay with the 8dn belt and i hope Ulmers upgrade kit for the 8dn belt will provide the fix. The frustration is buying a $11,000+ sled and having to dick around with this thing and spend more money.

Quick call to Ulmer seems in order. We had to unwind the secondary a bit as we were spinning the 153 Powerclaw we put on it on takeoff. Call Allen I am sure he knows what to do there.

Yep...I'm gonna call him to see what he says

 

[MCApex44]

I am getting Only 90mph @9050 rpms with 8dn belt and Ulmer clutch kit on a pretty long run on the lake. So i am getting more top end mph with 8dn but now she is a pooch from a dead stop. From a dead stop my buds Stock 09 Nytro pulls me in mid range by two sled lengths and also has more mph on the top end. My old Nytro xtx would beat that same 09 Nytro everywhere. The wifes 2010 Vector is eating this Viper up also. I am really frustrated with this Viper right now. Mine seemed better with the 8jp and ulmer clutch kit where it was beating a 07 F8 by 4-5 sled lengths in 500ft from a dead stop. Rpms were about 8700/8800 but getting any top end mph was a struggle with 8jp. i would certainly like to stay with the 8dn belt and i hope Ulmers upgrade kit for the 8dn belt will provide the fix. The frustration is buying a $11,000+ sled and having to dick around with this thing and spend more money.

You will have to add more weight to the primary to get the rpm's down to 8800 and you should get your mph back!

Sounds good...thanks!

 

[09nytro]

I want to ask a question !

What do you guys think will come in Allen's update / upgrade kit to run the 8 DN ?

What do you think needs to be done to make it work to its full potential ?

 

[DeerHuntr]

He told me that he thinks some machining would need to be done to reach full potential.

 

[BETHEVIPER]

kind of sucks for ulmer if he goes through the trouble to change a bunch of stuff so you can run a different belt, then yamaha comes out with an 01 belt update number that is just a shorter 8dn. All for not.

 

[YamahaTim]

kind of sucks for ulmer if he goes through the trouble to change a bunch of stuff so you can run a different belt, then yamaha comes out with an 01 belt update number that is just a shorter 8dn. All for not.

Well could be a break through with the 8DN