Belt Problems

[Dirt Digger]

Is any one running the ultimax xs 805 on the nytro. Just blew the second one. They go like a grenade at about 300 miles. The first was stock and second is supercharged. All clutch alignment is good, have vent kits. We ride deep powder and are hard on them but this sucks at 100 bones a peace. Just wanted to know if any one has had this problem with the ultimax belts. Thanks

 

[sledhead_m5]

Belt Issues

I have a MCX 180 kit on my 2008 Nytro and I'm having issues too. My alignment is good (checked by Alpine Motor Sports in Salmon Arm) and I have vented and geared it down. I got Alpine to install the smaller rollers (14.5MM) and a stiffer secondary spring and my last belt only lasted about 450 KMS before the cord started coming out. The clutches are hot! I tried the Ultimax as they always worked good on my Polaris sleds but it didn't hold up either. I keep hearing stories of Yammies running big horsepower and going 1500 miles on a belt. I'm not sure what to do next. If someone has has any ideas I would love to hear them. Sorry I didn't have a solution for you but I wanted to let you know that you're not alone.

 

[Thistledoo]

Lots of yamaha belt issues floating around all of a sudden and last season too....kinda wondering if yamaha is doing something different on the construction or maybe switched suppliers of belts??

 

[Chuckr]

Try NAPA

i never had any luck with ultrimax max belts on either my v-max or the sc/rx1
i have been using the same 2 gates kelevar belts that NAPA sells for 2+ seasons.It is a little cheaper and does not squeal all the time.

 

[modsledr]

Just curious why you guy aren't running the stock Yammi belt? There are guys running 20+ lbs with the stock belt.

If it aint broke, dont fix it.

 

[relentless rider]

I am having belt problems to on my t apex,have blown two in the last three rides.The last time it came apart,the strings wraped around my cluch and took out the seal on the side case cover.Im thanking maybe im getting snow dust on my cluches and its sliping just enough to get the cluches hot.Or maybe its the newer belts,i thank there like a 01 at the end of the part number,and the old (good) belts were a 00.maybe take a look at witch belt your running,if your using yamaha belts.

 

[Summitseeker]

I am having belt problems to on my t apex,have blown two in the last three rides.The last time it came apart,the strings wraped around my cluch and took out the seal on the side case cover.Im thanking maybe im getting snow dust on my cluches and its sliping just enough to get the cluches hot.Or maybe its the newer belts,i thank there like a 01 at the end of the part number,and the old (good) belts were a 00.maybe take a look at witch belt your running,if your using yamaha belts.

I have a very similar problem. I was also blowing belts last season until I got the right clutching configuration and I was good for a while. However something has changed recently and I can't keep belts on the sled. I have replaced both springs and have played around with my shockwave but no change. Your theory on a new Yami belt may be it?!?! I have to look at that when I get home today! It is definitely a heat issue as my clutches are too hot to touch. If anyone has an "old 00" belt to test the theory it would be good to know!

 

[twincam88]

are you guys doing proper belt break in? you NEED to ride easy on a new yamaha belt for about 60-80 miles. iknow its hard to do but if you do that they last a long time. if you dont do that they grenade in about 60 miles. guys here have 2000 miles on a belt with a mcx 240. also scuff your clutches with scotch brite or emery cloth working from the outside in. it takes the glaze off the sheaves.

 

[Dirt Digger]

I have not had problems with the yammy belts but have not ran them much. We went to the ultimax xs because we were told the yammy belt was to hard and just slipped.

 

[Nytro MTX Sweden]

It’s a common problem on Turbo Nytros here in Sweden, cord coming out, Blown belts, overheated clutches!<O</O
I have had two Nytros and both had this problem, several of my friends to!<O</O
If we are lucky a belt last 400 km!!<O</O
We have tried almost everything without improvement!
<O</ONow I have a Tapex and no beltproblems!<O</O

 

[twincam88]

the apex and the nytro run the same belt (8dn-1764-01) so i wonder why apex's dont have belt problems?

 

[ARMac]

00's last 100-200mi longer than '01 on a Nytro, but they still grenade. And they aren't made anymore. Apex runs lower clutch rpm (i think) thats why belts last longer. With a little break in my '01s last 300-400mi at 17#boost. Haven't found anything better than Yam belts.

 

[BLUE BLOOD]

the apex and the nytro run the same belt (8dn-1764-01) so i wonder why apex's dont have belt problems?

IMO THE APEX HAS A MORE RIGIT CHASSIS THEN THE NYTRO, LESS FLEX AND TWIST UNDER BIG H.P. #S = LONGER BELT LIFE.

 

[boostedballz]

Something that I believe is being overlooked here is clutching. Big weight and big helix means small belt life. Most of you sound like your running boosted sleds. In my experiance over 47 degrees of helix angle will double you clutch temperature unles you have the primary properly set up to do so. The guys running the lighter 8BU set up up front can get away with an up to 51 degree helix with the apropraite secondary spring and preload. You can also run a heavier set up in the primary with a lesser helix angle (39-45 degrees) and achieve a similar result.If any one of these factors don't mesh with the others you can do all the aligning and venting you want but your belt life will not improve. I could be missing something but thats my 2 cents.

LL

 

[Shermanator]

I think you've got it right boostedballz, my clutches are all stock except for a softer primary spring, thats it. I'm not getting any 1000 miles out of a belt but 600 miles is common..........Sherm

 

[SLY]

The Ultimax belts just do not hold up. Tried them myself after I heard that same softer belt comment a few years back. Went through 3 in short order before switching back to 8DN Yamaha belts. Ran the 8DN on all my turbo Vector, Nytro and Apex motors since with great success up to over 300hp. Gotta get the clutching/gearing right, not be too greedy with helix angles and keep the snow and oil off the belts/clutches. I usually clean my clutch faces and belts about every 300k and replace a belt if I see damage/cord pulls on the edges but 1000k+ should be no problem on a turbo.

 

[Linc]

Too stiff of a secondary spring will eat up a belt too, you'll need to run more primary weight to overcome the the stiff secondary, then you need a stiff primary to hold back the the extra weight, it's all a balancing act. The secondary tells the primary what to do, and when you run a steep secondary and a stiff spring you're compounding the belt heat problem.

I had a MCX nytro in the shop two weeks ago with the same problems, I switched out the MCX weights, loaded up the some 8bu's, 14.5 rollers, tightened up the belt deflection, put a steeper helix ( Shockwave ) and lightened up the the secondary spring, ( Cat Yellow ), and most importantly, scotch brite the sheaves! No more issues.

 

[Summitseeker]

Too stiff of a secondary spring will eat up a belt too, you'll need to run more primary weight to overcome the the stiff secondary, then you need a stiff primary to hold back the the extra weight, it's all a balancing act. The secondary tells the primary what to do, and when you run a steep secondary and a stiff spring you're compounding the belt heat problem.

I had a MCX nytro in the shop two weeks ago with the same problems, I switched out the MCX weights, loaded up the some 8bu's, 14.5 rollers, tightened up the belt deflection, put a steeper helix ( Shockwave ) and lightened up the the secondary spring, ( Cat Yellow ), and most importantly, scotch brite the sheaves! No more issues.

I also switched out the MCX weights last season and went to 8BUs fully loaded with 14.5mm rollers and a blue/white/blue Primary spring. I am running a shockwave helix (set to 1.5 turns) in my secondary and had a green arctic cat spring wound to 0 and 1. I put in an EPI purple spring last night wound to 0 and 1 and will try it tomorrow and see how much difference that makes.

Linc...you mentioned you went to a yellow AC spring. That would be a HUGE difference for me going from 280 pound spring tension to 92 pounds. I was going to try the EPI purple that is rated for 260 pounds. I know you know what you are doing so now you got me wondering if I should try the AC Platinum or Yellow?!?!? Thanks for the tip!

0648-732 Green 280 lb
0648-693 White 260 lb
0648-662 Platinum 180 lb
0148-227 Yellow 92 lb

 

[Linc]

I went for the yellow because the I couldn't weight the ramps enough to combat over rev, I gave it more twist for back shift, I also took out the b/w/b and put a softer spring in the primary.

Years ago Dwayne Watt gave me some valuable info on clutching when I used to run his encapsulated roller set up, that clutch kit had almost Zero spring torsion and a very light spring, i'll go back to that type of set up when I get a chance to test for a day. Whenever you run a super stiff secondary, you'll always have to run really heavy weights to make it move.

 

[Summitseeker]

The purple EPI spring must have made a difference! Blow over the head pow and blue sky today and no signs for of belt wear. She was working hard!!