Change gearing to climb better?

K

kimoaj

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Hi guys!

I love my Viper Mountain 144", (all stock except aftermarket canister) but from time to time I get frustrated when riding in powder, it doesn`t climb well.
My friend with the V-Max 4 121" 2.25 finger track climbes just as well as me.
Same does my friend with the Doo 2003 MXZ 800 121" , something just doesn`t seem right.

What is the stock gearing?. I wonder if the previous owner changed the gears in order to pull a "trailer" after the sled.
It`s seems like I`m missing some track speed.
It keeps a steady 8500rpm no matter how much snow/steep/load.

Can I change the gears and get more track speed = better performance in the hills?. Or will I need triple pipes and a longer track?.


I love the Viper and I wount trade it for anything in the world, but I want it to climb better.


Any suggestions?.

Thanks.


Joakim
 
Mtn Vipers when stock are geared a little high and the secondary tends not to back shift fast enough to stay on the power curve. I would change the twist to 80 or 90 degrees. 80 if between 0 and 6000 ft in altitude, 90 if more. That is a free 30 minute fix to try. If still not happy, than lower the gearing a little. I ride at 8500 plus feet, 21 x 40 gearing with 8 tooth drivers, 90 degrees of twist, 160 hp and climb with anyone except the 162" track sleds.
 
Hi guys!

Aha so I`m totally wrong when I think that the problem is that it`s to low geared?.

I`ve actually forgot how to calculate the amount of twist, even though I did it several times when I worked at the Yamaha shop, can you tell me how A K MtnViper?.

Should I notice a difference after changing the twist?.
I will try to change it and then let you know what I think.

Btw A K MtnViper are you running stock CDI box and stock head ?. I`ve heard rumours that the Vipers doesnt hold up that well when you pipe them?.

Hmm :)
 
The spring holes are numbered, sheave hole (1,2,3) and helix hole (0,3,6,9) add the two numbers together IE 2 and 6 and mutiply by ten = 80. I think i have this right, its been awhile for me also. Stock CDI and head with no problems.
 
Hi A K MtnViper

Today I removed the secondary and found out that the spring was set at 90degrees.
I was kind of surprised, I know it basically should be a step in the wrong direction but I changed the setting to 80degrees.

At first I think it seemed like the sled got a little lazier at lower rpm but (it might be imagination) it seemed like I got more track speed. I wasn`t able to test the topspeed, but I got to ride it in some pretty steep hills and I didn`t get stuck.
Although it might aswell be different snow conditions (guess the snow is more packed now, since last weekend).

It was very bad riding conditions today with low clouds and snow so I wasnt able to test it 100%.

Wellwell I will get back to you when I get to test it properly.
 
Best way to test is to see what track speed you're getting, and then change and run again. Best to do it on same hill on same day, as snow conditions, etc., will change track speed ( as far as secondary setting, I would'nt want to change gears in the field, lol). If the twist is too low, you should be able to watch your rpm's as you're running and tell if its not backshifting correctly, you will see your rpm's drop a little because of bogging right before it shifts. I tried running 90 degrees on mine, and lost some track speed. I think the tight twist was making the secondary hold back the primary, I dropped back to 70 degrees and it pulled my rpm's down about a 100 (I was over turning a little anyway) and I gained some track speed. As far as pipes, I love mine, but it took me a while to figure out the powder bog cure. It's possible that lower gearing will help you gain some track speed, but it will also require you to play with the weights in the primary. I've read that proper gearing on a mountain sled should allow it to only be able to do 80-85mph on top end. Fine tuning like this takes time, patience, money for rivets and gears, and lots of test runs. There's definitely room for improvement, I would think your 144 should be able to get around quite a bit better in the powder than 121's. Suspension could also help, you don't want a really stiff setting that pushes your track down into the snow and causes bad trenching. I have mine only as tight as necessary to not have it bottom out in bumps, and I don't hammer it real hard in bumps anyway. It should also transfer and pack the skis, but only enough to lift them slightly. Too high of ski lift will pull some of the front of your track off the snow and basically make you a shorter track as far as footprint goes.
 
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