SR Viper, clutching, belts, gearing information

[Srxspec]

I will share what I have tested and what I have found using the RTX/LTX models as a testing reference.

1. 8JP belt with stock clutches will be limited to approximately 93-95 mph.

2. 8DN belt with stock clutches will be limited to approximately 103-105 mph.

3. 8DN/8JP belt with secondary setup properly will allow you approximately 113-115 mph.

4. 8DN belt with both primary and secondary setup to match the belt properly will allow you approximately 120-121 mph.

The stock secondary setup with the 8JP belt will stop your belt approximately 3/8" to 1/2" below the top of the primary clutch due to two reasons, the stock secondary will stop shifting at that point and this stops the belt from going any higher in the primary as well.

Now if you install an 8DN belt you can get the belt to approximately 5/16" from the top of the primary and gain some top speed in the correct conditions.

Stock secondary clutch travel is approximately 0.870" and after setting up the secondary properly you can achieve just slightly over 1" of travel (1.008").

Stock primary clutch travel is approximately 1.104" of travel and after setting up the primary properly you can achieve 1.317" of travel and get the belt all the way to the top of the primary clutch, leaving no clutch face surface unused, in the correct conditions.

This is an informational post from Ulmer Racing, call us if you have questions, I do not want to offend or argue with anyone, as it will not help anyone in the end, and there is 100 different ways to alter clutching via the clutch arms, springs, helix, etc, but when the belt is limiting the shift ratio, changing those items will only do so much.

We will offer primary & secondary machining/setup process for those that are interested. You can purchase a clutch kit to match it or if you already have a Ulmer Racing clutch kit I will modify it to work properly as well. If you want to continue to use your own clutching, but want the clutches machined properly with some advice on how to setup your helix/spring I can do that as well.

Phone: 605-387-2833

Email: Srxspec@Gwtc.net

 

[Studroes144]

Very interesting info. Are you more the less saying that unless the 8dn belt is used, you won't ever be able to use the complete surface of the clutches? On my setup with the 8jp belt I have 1/4" at most on the primary that isn't used..it's more than likely less than that but I know my belt never reaches the complete top of the primary

 

[YamahaTim]

Great info Allen!! Man 120 that's hauling

 

[DeerHuntr]

Interesting read. Not arguing at all because I am clueless about clutching for the most part but how did I reach 103 Mph speedo /101 gps with the 8 jp? Are they that inconsistent in length and width?? Trying to learn more about this.

 

[sixstringorsnow]

Wow. Those are really high speeds. Is this a stock viper? I have 3000 miles on my sled and have only seen 105mph. I have tried different clutching and haven't got those speeds. That is awesome, almost hard to believe. I was waiting for the summer to talk to you about what to do to my viper. I would like to keep it as quiet as possible and want to get as much HP without a turbo. I miss my 150hp and would like it back. If you are getting these numbers sign me up.

 

[MCApex44]

This information just gave me a chubby. That is a snowmobilers porn...ha!

On a serious note...good work and nice findings Allen!

 

[Srxspec]

Very interesting info. Are you more the less saying that unless the 8dn belt is used, you won't ever be able to use the complete surface of the clutches? On my setup with the 8jp belt I have 1/4" at most on the primary that isn't used..it's more than likely less than that but I know my belt never reaches the complete top of the primary

Without reworking your primary clutch you will not see that 1/4" at the top get used. This is common on all Yamaha models as the primary clutch won't allow it to shift it all the way out, it's just on the Viper with the 8JP is even more sensitive to it box stock.

Interesting read. Not arguing at all because I am clueless about clutching for the most part but how did I reach 103 Mph speedo /101 gps with the 8 jp? Are they that inconsistent in length and width?? Trying to learn more about this.

Conditions will still dictate top end speed. Variances in belts themselves can dictate a few MPH either way as well. I have only measured a handful of 8JP belts (I could measure more, but don't want to take them out of the pretty new packaging they are in).

8JP belt width = 1.350" avg
8JP belt thickness = 0.640" avg
8JP belt circumference = 44.250" avg

8DN belt width = 1.360 avg
8DN belt thickness = 0.630" avg
8DN belt circumference = 44.5625" avg

Wow. Those are really high speeds. Is this a stock viper? I have 3000 miles on my sled and have only seen 105mph. I have tried different clutching and haven't got those speeds. That is awesome, almost hard to believe. I was waiting for the summer to talk to you about what to do to my viper. I would like to keep it as quiet as possible and want to get as much HP without a turbo. I miss my 150hp and would like it back. If you are getting these numbers sign me up.

A "stock" (naturally aspirated) Viper will likely never run above 110-113 mph, it will take a turbo to go above that. Of course, conditions also dictate your top end an immense amount. It is amazing what the difference between a complete hardpack/ice road can be versus an inch or two of snow.

 

[fx-treme]

Yes, you will have a new customer. Thank you just what I was waiting for.

 

[TD Max]

So to recap:

1) Physical/mechanical conditions are limiting top speed/full shift

2) The numbers posted are THEORETICAL based on conditions and HP lining up correctly.

 

[TurboJamie]

We have found the turbo to be done at 117 mph on an ltx using the 8jp.

 

[09nytro]

So the 3rd one is a "stock" viper then right !

The 4th one is a turbo viper right ?

Those are some good #'s for sure !

 

[Studroes144]

Your testing shows that speeds are greater with the 8dn belt but what is the difference that is making this happen? Is it just the little bit of extra thickness? I'd be curious to try making the 8dn work with my setup but I never had an issue with the 8jp in the first place other than dust..on a very hard packed snow or ice I can consistently see 101-102 mph in a 1/4 mile with no performance parts other than clutching. Is this just a quick fix for the guys with low speeds or can everyone benefit from using the 8dn. I just don't want to spend all the time swapping out clutch parts again and testing and tuning if it isn't going to gain me anything

 

[stingray719]

Your testing shows that speeds are greater with the 8dn belt but what is the difference that is making this happen? Is it just the little bit of extra thickness? I'd be curious to try making the 8dn work with my setup but I never had an issue with the 8jp in the first place other than dust..on a very hard packed snow or ice I can consistently see 101-102 mph in a 1/4 mile with no performance parts other than clutching. Is this just a quick fix for the guys with low speeds or can everyone benefit from using the 8dn. I just don't want to spend all the time swapping out clutch parts again and testing and tuning if it isn't going to gain me anything

8DN belt is slightly longer and gives you an ever so slightly higher gear range. I do not care about top speed I put the 8DN on because of the 8JP slipping and causing RPM hunting on our Viper.

 

[Srxspec]

Your testing shows that speeds are greater with the 8dn belt but what is the difference that is making this happen? Is it just the little bit of extra thickness? I'd be curious to try making the 8dn work with my setup but I never had an issue with the 8jp in the first place other than dust..on a very hard packed snow or ice I can consistently see 101-102 mph in a 1/4 mile with no performance parts other than clutching. Is this just a quick fix for the guys with low speeds or can everyone benefit from using the 8dn. I just don't want to spend all the time swapping out clutch parts again and testing and tuning if it isn't going to gain me anything

Something I have not tried yet, but want to, is to re-gear this sled and use the extra shift ratio to maintain approximately 110 mph top speed, but hopefully pick up some "snap" and acceleration as well, without compromising top end speed.

The stock 24/50 gearing with the 8DN/8JP belt with properly setup secondary, but no extra machining in the primary, is pretty much done at 113 mph @ 9150 rpm (full exhaust, K&N intake, PCV).

 

[TD Max]

So you are saying take this setup:

4. 8DN belt with both primary and secondary setup to match the belt properly will allow you approximately 120-121 mph.

And regear to max theoretical closer to 110mph?

That makes good sense to me especially if the NA engine will never get to 120.