How much does altitude affect clutching?

[hugger70mtnmax]

Went for a ride today. Wow awesome snow. Rode bottomless powder most of the day. Only problem was the sled was only pulling 7900-8000 rpm all day. I was riding at 9500 feet all day. I usually ride from 8000-8600 feet. Does altitude make much difference from what you guys have seen on these sleds or should I be looking into the clutching. Most pulls it was getting about 32-33 mph.

Sled is an 09 with 153 in it all stock.

 

[Mtnviper]

Yes it does, although they are not as sensitive as carbed 2 strokes.
Snow conditions will effect it as well. Usually wet heavy snow will pull the rpms down some. Since you were riding in powder, I would reduce the rivit weight in the primary.
I would start with removing approx 2 grams, and try it to see if it get's you closer to 8600 rpms.

 

[hugger70mtnmax]

Thanks. I'll try that and see what happens. I'm assuming that I want too take that out of the tips?

 

[Mtnviper]

Thanks. I'll try that and see what happens. I'm assuming that I want too take that out of the tips?

Yeah, I would pull it out of the tips first.
Sometimes you will need to pull some out of the heel, but only if it is under-reving pretty bad at low speeds.

 

[hugger70mtnmax]

So I pulled the weights out of this thing and there are no rivets in them. The weights are 8fs weights.
They are 67 Grams. The spring is a gwg. Is is possible that it needs a stiffer spring, or will that hurt my low end engagement point? How should I take weight off where there are no rivets? Grinder?

 

[akvector]

I think most people use a belt sander and do a little at a time. How low are you? What helix and what secondary spring and wind are you using?

I attached a chart for you on the primary springs. Unfortunatly to keep the same engagement the GWG has the highest total force. You could go to the pink green pink or jump all the way to orange silver orange but your enagagement rpm will drop with both.

 

[Mtnviper]

I've used a stationary belt sander as akvector mentioned. Also it's best to use weight grinding holding fixture tool and a gram scale. So you can make sure that mass is removed in the same location on each weight and the same amount.
Before grinding though I would check over the clutching componets for wear. Also there is a chance that the stock spring may be sagged, which can lower rpms.
A "rough idea check" can be done on the spring, by comparing it's free length to the spec. If it's shorter then, it very likely has lost some tension.
If everything is checking out, then I would try the org/sil/org spring mentioned above. To increase engagement RPMs, you can always add up to 3 engagement shims behind the spring.
If the new spring raises the shift RPMs to high, you can always add rivits to your weights since all three holes are empty.
RPMs can be increased by winding the secondary spring tighter also. Although this is not the best way to control shift out RPMs, since you'll usually loose clutching efficiency.

A general rule of thumb is, tune the RPMs with the primary clutch. Tune the up/back shift with the secondary clutch.

 

[hugger70mtnmax]

Thanks for the help guys. I rechecked the weights and they were at 65. I dropped them down to 62 and I really don't think I can take any more off without getting to close to the holes. I rode it again today and the rpms were up to around 8200 so still a little low. I think I will have to work with the spring a little to get it the rest of the way. My track speed is only about 33-34 so I hope if I get the rpm right it will help with that.
On the secondary I didnt take it apart to see the spring but it is wrapped at 80

 

[akvector]

If it were me I would change your primary spring and if that raises too much I would go to the smaller roller. The smaller diameter roller will allow more side force from the primary on the belt ensuring no slipage in the primary. when you go to the smaller diameter roller you will lose rpms so you need to adjust for that.

I have not really played with mine but I know I am hitting the rpms that i would like to see.

 

[hugger70mtnmax]

Well finally got my clutching issues figured out. I burned another belt after about three hundred miles. So I took it to the dealer cause I thought it would be under the warranty. Turns out the secondary alignment was way off. Bad thing is they say that wasn't covered because it's a setup issue. At least it got figured out. Only bad thing now is the rpms are too high since I took weight off. Revs to 9300 on the trail and 8900-9000 off trail. Oh well guess I'll have to add some weight back in.

I do appreciate everyones help but just thought I would bring this up so others might check this before going other directions and missing the real problem.

 

[clatla]

I have a question about your secondary alignment being off. I came from a SkiDoo with the fixed secondary and know of alignment issues but Yami's secondary floats (like they should). What was the cause of the secondary being off? How did they fix it?

 

[hugger70mtnmax]

The secondary has shims that are on the shaft with the clutch that align it to the primary which allows it to move in or out.

 

[clatla]

Would you be able to remove a shim or 2 and let it float?

 

[akvector]

So here i am tearing up the powder today and i feel my belt starting to go so i stopped and sure enough it was fraying and the cords were coming out. I would have to guess that i had 500 miles on this belt. I proceeded to put my spare in that had about 300 or so miles. I made two runs up the hill and boom there it went. I limped it out on the 1st belt. The second belt actually turned over on me what would cause that?

I so did not want to mess with the clutching this year but I think it is time for smaller rollers and the gwg spring as i have the bwb in mine.

 

[philsummers21]

I wouldnt blame it all on the primary. On my nytro i ran the gwg and stock weights. I ground the tips to i think 63grams. Secondary i had the Cat Yellow at 10degrees and stock helix it ran well. I know some run the pink secondary at like 110 degrees and like it as well. Make sure which clutch is slipping (making Heat) then start fiddling with your clutching. If you have the stock secondary spring wind that sucker all the way and see if that helps.

This was for 8500-9500 ft