susp setup = top speed/handling?

[SRXracer]

found a service manual online for the xf 7000, the viper twin, and it has a very good section on suspension setup for handling. Some of it is a little counter intuitive, so I would highly reccomend a read thru it. It starts on page 168. One thing it mentioned was to cure darting, actually decrease center shock pressure to put more track on the snow under deceleration... interesting.

It also mentioned how the rear skid setup is very sensitive to adjustments and will effect top speed - "slows down by 5-8 mph".

Here's the link: http://countrycat.com/ccstore/kbase/snow/2014/ZR_XF_M_4-Stroke.pdf

from page 169:

Having very light front arm spring tension is desirable. When riding in 4 in. or more of snow, the machine will be quicker if the front spring tension is adjusted lightly.


If the spring tension is adjusted too stiff, the track angle at the front of the skid frame is steep. This steep angle prevents the snowmobile from getting up on plane and slows down by 5 to 8 mph. Also, the following could occur.


1. Slows machine down in loose snow.


2. Causes the snowmobile to dart and dive as a result of less track on the ground on deceleration.

 

[Yamadog]

There your sign!!! I tell you this sled will bleed energy badly if the skid is not set up properly and most guys are not playing with the front skid shock. I ran into a guy in the UP 2 weeks ago that was on an xf7000 and he ran across a small lake with me and was hitting 102 easily (LTX Version). But he told me he played with the rear skid set up for half of last season and a lot of clutching work. Out of the box he was 85 to 87 max on flat hard pack. And when you think about it my 2015 Polaris Pro S 800 SB with a claimed 162 ish hp will only do 102 on GPS 108 on speedometer.

 

[Yamadog]

WOW look at pg 9 the gearing section the 9 tooth 2.86 pitch with 24/35 gears will do 161 mph - I better get more life insurance!!!!

 

[bleedyamaha]

WOW look at pg 9 the gearing section the 9 tooth 2.86 pitch with 24/35 gears will do 161 mph - I better get more life insurance!!!!

Is this the pipe dream manual or what?

 

[Yamadog]

well you would have to be smoking something in a "pipe" to believe it!!!!!! if it had a anti matter containment field it would do Warp 5...Make it so number 1.

 

[stingray719]

found a service manual online for the xf 7000, the viper twin, and it has a very good section on suspension setup for handling. Some of it is a little counter intuitive, so I would highly reccomend a read thru it. It starts on page 168. One thing it mentioned was to cure darting, actually decrease center shock pressure to put more track on the snow under deceleration... interesting.

It also mentioned how the rear skid setup is very sensitive to adjustments and will effect top speed - "slows down by 5-8 mph".

Here's the link: http://countrycat.com/ccstore/kbase/snow/2014/ZR_XF_M_4-Stroke.pdf

from page 169:

Having very light front arm spring tension is desirable. When riding in 4 in. or more of snow, the machine will be quicker if the front spring tension is adjusted lightly.


If the spring tension is adjusted too stiff, the track angle at the front of the skid frame is steep. This steep angle prevents the snowmobile from getting up on plane and slows down by 5 to 8 mph. Also, the following could occur.


1. Slows machine down in loose snow.


2. Causes the snowmobile to dart and dive as a result of less track on the ground on deceleration.

Interesting. I found taking weight off the skis gave me noticeable improvement to my top speed. Now granted I am geared down but I still pull hard to 80 - 85. See how much drag your skis cost you when the snow is wet and sticky. I have no doubt the above might be correct in just the right snow but have not seen it to be true in y testing.

NOS-PRO needs to chime in here as he put 153 Cat rails on his XTX which have different mounting holes for the front skid shock adding spring pressure and making the skis much lighter on the snow. He also put on a 153 2.25 paddle track, and I will let him state his results. Terry?


.

 

[cannondale27]

X2 Stingray 1/2turn tighter on my center shock spring keeps the skis off the ground as far as I want. Much faster when they arent dragging in snow.

 

[Studroes144]

I did some back to back top speed testing last year with my ltx se, outcome was exactly what is stated in first post. With center shock and front shocks adjusted on the stiffer side sled felt to transfer a bit better, but ultimately it was slower, loosened center shock to just a bit of preload and softened front floats from 80 psi down to 65 and it was 6 mph faster with no other changes in the same field within 20 mins of each other. I also did it making a fresh track thru the snow every time so I knew there wasn't any contributing factor. Another big thing was track tension, a lot of speed lost with a track that's too tight on the coupled versions

 

[40TH FX NYTRO]

Studroes 144 have you pulled up your limiter strap or is it all the way out

 

[Studroes144]

All the way, pulling it up even one hole gave it zero traction

 

[stingray719]

Could one of you LE guys with the top speed problem put your front skid mounting bolt in the lower hole and test? I wonder if you are not hitting the tunnel protectors at speed or at the least creating drag around the heat exchanger.

 

[cannondale27]

Don't forget track ballons at top under deceleration or braking not acceleration.

 

[cannondale27]

My protectors are covered in rubber from track.

 

[stingray719]

Some of the guys that put on the 3 inch lug track for the mountains did not put on the 7 tooth drivers for clearance and suffered noticeable loss from the fan effect with the paddles being so close to the heat exchanger. Yes that is a mountain sled but I would think the same effect could happen here....maybe.

 

[tapex_07]

Some of the guys that put on the 3 inch lug track for the mountains did not put on the 7 tooth drivers for clearance and suffered noticeable loss from the fan effect with the paddles being so close to the heat exchanger. Yes that is a mountain sled but I would think the same effect could happen here....maybe.

Yes tunnel pressure is a robber of track speed! Either smaller drivers, drop and roll, or track porting (I don't recommend) are the only options to help relieve that tunnel pressure created by the close clearance/ big paddles.