Boosted nytro blowing belts

Nytro907 · Mar 2, 2009

I have an 08 nytro mtx with impulse gt2860 turbo. I've upgraded the secondary spring to AC green on 0/1 settings. The primary has a blue/brown/blue spring with STM adjustable weights. The clutches are aligned and the motor revs at about 8700. The difflection is in specs. Even tried changin to ultimax XS belts but know still blowing belts almost every ride... Any suggestions?

0007 · Mar 2, 2009

First you need to decide which clutch is the problem, blowing up belt's is always slippage, is it happening at higher speed's or lower speed's?
slippage at high speed is most common with a turbo and mean's as the square inches of belt contact decreases in the secondary it start's to slip
some guy's have actually destroyed the secondary
You got melted belt on the secondary sheaves halfway down or so?

snowy1 · Mar 2, 2009

need alittle more information, what rollers in the primary, what helix what is the angle, what gearing, and you need to use the yamaha belt, give us your complete clutch set up and we can help you out. should not be having belt problems.

Nytro907 · Mar 2, 2009

Belts have been blowing at higher speeds but the secondary doesn't show any sign of the belt melting in the sheaves. The primary sheaves however does about half way down. I've tried stopping for lengths of time for the clutches to cool. Both clutches are usually too hot to touch for any lenght of time

zebiraross · Mar 2, 2009

Do you have the new agressive stm 55g weights? Those are way finicy. If you load the toe and leave the heel empty the primary won't shift out. If you load the heel and leave the toe empty you get SERIOUS belt slip on top end. I bet that is what is going on if you have the toe empty. You have to distribute the weight in both the heel and the toe. leave the middle empty if you have to.

Nytro907 · Mar 2, 2009

Running 12 lbs of boost with stock gearing, stock helix, and the rollers have been changed to 14.5mm

snowy1 · Mar 2, 2009

you need to change the helix to a 45 or 47, the stock is 39.and as zeb said distribute your wieght,

Nytro907 · Mar 2, 2009

I checked the secondary sheaves again and there is belt residue at the base of them. The primary weights are setup with the 7gram tungsten at the heel on either side. The middle and toe have 3 washers each but r only on one side

snowy1 · Mar 2, 2009

most of your set up sounds pretty good, start with replacing the helix and see what happens from there, and besure to use a new yamaha belt.

HYFLYR · Mar 3, 2009

Im running the same turbo as you, same clutch springs, same helix, just a different weight setup and havent burned one belt all year.

One thing to look for and has also happened to me is the bushing on the stm clutch weight seizes and doesnt shift properly, very harsh out at first and slow to shift back. Probably not your issue but something to look for.

I have my weights setup with a tungston on the heel and mid, and 4 grams at the tip. Also have the 14m rollers. My clutches stay warm but never hot, can always hold a hand to them to check even in the deepest snow. No extra venting or anything, although im not running a headlight but do block it off when super deep out.

When you put the secondary spring in did you give it a slight twist? Your clucthing is very similar to mine so im wondering where you might be having a problem. Have you checked to make sure your ramp shoes are still in good shape? Does belt squeel at idle?
Did you make sure to get all strands of belt out after the first one blew, could a piece of tangled in the primary somewhere. Just throwing out ideas to look for.

Oh and when you say stock gearing do you mean 20 or 22 top gear, some dealers dont regear for ak lower elevation riding and leave the 20t gear in instead of switching to the 22 suggested for sea level, im running the 22.

Ak nitro · Mar 3, 2009

Thats a good point about the gearing hiflyer, I ride with 907nytro everyweekend and our setups are almost exact, and I do not have near the belt issues he has, the only diff is I have the 162 and he has the stock track, and I run the shockwave. We both rode the stock tracks all last winter and had no belt issues, but the snow really sucked last season compared to this season, we have not rode one day yet this year were the snow has not been over the hood. I did notice his chaincase bolt turns in a lot farther than mine. We could pull them apart and check, I just hate going into that chaincase, what a pita. We bought the sleds different places so the gearing may be the issue.

Nytro907 · Mar 3, 2009

The gearing is 22/40. The ramps still look in good condition. I took both clutches off the sled, and cleaned every area that i could reach with soap and water, so I know for sure there are no strands of belt left on them. One thing i noticed on the sec. sheaves were some super small holes midway down. When installing the sec. spring I did give it a slight twist to get the helix in place. The belt doesn't squeal at ideal. Today I'm plannin on ordering a shockwave helix. I might try runnin the same clutch setup as Hyflyr. What areas do you usually ride at?

Thistledoo · Mar 3, 2009

needs to be 20/40 at least....mine is 19/40 and change that helix.....it will work alot better.

HYFLYR · Mar 4, 2009

I generally ride anywhere from sea level to 4.5k feet. All our riding areas are low down here, mountains start from the water and go up from there.

With running the longer track you could probably run the steeper helix like mention above and or the shockwave and see improvements in belt temps. Also, the shockwave is nice for fine tunning a couple hundred rpms with changing snow conditions. I usually like to gear down but for whatever reason with my setup this season i havent felt the need to, whether it be the elevation im running at or track/clutch combo. If i were you though i would only change one thing at a time and go from there, the biggest mistake alot of people make is they change a whole buch of things at once and dont really know what did what, if it helped or hurt performance. Good luck with it.

You going to be running around at arctic man?

Ak nitro · Mar 4, 2009

Hiflyer I may have confused things a bit by chiming in, but I will try and clear things up. I have the 162 with the shockwave and I have no belt issues. Nytro907 has the stock track and has belt issues, last winter we both ran the same setup, same turbo, same sled, same clutching, no belt issues. This year 907 nytro starts showing threads and breaking belts, so we start to change one thing at a time, we start with a new primary spring, the next week a artic cat green secondary spring, the next week 14.5mm rollers, next week he has the alignment checked at northen power sports and have them look it over, we check the clutchs for scratches,etc. So his next plan is going to be to try the shockwave. It is just strange that all last winter he ran the clutchs with only supertips and had no belt issues, I know the springs wear out and we changed them, but we are making one change at a time to try and get this figuered out. BTW we will both be at A man, we should go for a ride.

Tookes · Mar 4, 2009

Shouldn't our AK dealers have changed the 16mm rollers to 14.5 rollers when they made the changes for Alaska altitudes during the initial setup of the sleds?

Nytro907 · Mar 4, 2009

Got the adjustable shockwave installed with the AC green spring set at 0/1, with clockwise twist on the spring. Gonna break in the 2 new yamaha belts around some trails and will see how the weekend goes.

Tookes · Mar 4, 2009

This is what Paul told me.

Secondary
Cat SnoPro Green spring, set at 0,3
Shockwave helix at 1.5 turns out

snow4blood · Mar 5, 2009

i think your nytro's clutches are getting too hot. you will have to get some vents....the belts just cant hold up to that kind of heat.....my uncles boosted nytro was doing the same thing, he put some vents on the clutch side and hasent blown a belt since.

Nytro907 · Mar 5, 2009

Last night I installed the front lower vent and back lower vents from 2 cool. Does anyone know how much snow passes through them?

Boosted nytro blowing belts

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