850 Belt life - A band aid Journey

bcpowder · Apr 19, 2018

Hi team,

Just to follow up on this post i originally put up with my 2017 850 (link below): I figured I'd give some history, and my thoughts on the My2019 belt life updates.

https://www.snowest.com/forum/showthread.php?t=432597

Following the post above, I did get my alignment corrected, and it delivered no improvement to my belt life. I think it actually got worse. I ended up trading my 2017 in for a 2018 850 which obviously had the My2018 belt life upgrades. This delivered some improvement to belt life, but it was still totally disappointing.

I would say the My2018 updates took me from 100km per belt to 200 km per belt.

On the 2018 sled my alignment was spot on. I can confidently say that this is not the global issue with this sled, although it may be a compounding issue on some sleds. I spent considerable time playing with different clutch calibrations to see if we could refine shift consistency to stabilize peak rpm, minimize over rev, and improve back shift. I would say this process got me closer to 300 km per belt.

For all those wanna be sled mechanics out there, we don't need your thoughts on belt deflection, or belt break in procedure.

My opinion after running hard at belt issues on 2 years of these selds, is that the fundamental issue is excessive engine movement / vibration due to the long stroke 850. BRP is trying hard to counter act this with their "wobble clutch", and continually stiffening motor mounts in each years Belt life updates.

unfortunately, upon watching the unveiling of the MY2019 belt life upgrades, I've had to move on to a mountain cat as BRP has only confirmed to me that there is no way to correct the vibration in the 850 power plant...only band aids to put over top of it.

As can be seen in the 2019 updates, BRP is again stiffening motor mounts, however it clearly doesn't solve the base issue of excessive motor vibration. This which is confirmed by the fact that their second update is a fan clutch and radical air movement technology to run past the clutches to deal with what they know is excessive heat being generated by the engine vibration. The 3rd update of the belt guard is nothing more than a distraction, which is confirmed by them in their roll out and not a wide spanning issue.

At the end of the day, if you ride the 2019 850 hard in the mountains, i would predict 200-400 km per belt. The regular rider may be able to get around 1000-2000 km. The disappointing part here is that on the xm, these same riders now getting 1000 - 2000km, used to get 3000 - 5000 km per belt. BRP will isolate the hard riders and rider blame, and eventually you will be on your own with an under performing machine, paying for belts, and dealing with the compounding wear and tear of a constantly overheated and shock loaded crank.

Good luck boys.

BILTIT · Apr 19, 2018

Sorry to hear about the mountain cat...

All kidding aside, good to hear some honest info/thoughts/opinions.

Sent from my SM-G925W8 using Tapatalk

sledhead_24_7 · Apr 19, 2018

You are most likely right, unfortunately. Which most likely put me on a Alpha Cat or dare I say a Pro 850 in the next year or 2.

I also had 2 model years of 850 blown belt issues. 14 belts between the 17,and 18 both around the 850-950 mile mark.

Band aids on a chassis flaw to cover over the flaw, does not fix the flaw obviously.

DITCHBANGER · Apr 19, 2018

Alpha cat is tempting, buddy just ordered one, doo is on the 3rd year and still doing updates to a problem that should have never been a problem from the get go.

Illinoispowder · Apr 19, 2018

Belt life

If engine mounts are the "real" issue, why did the 2017 trail sleds with soft mounts have a much lower failure rate? Proper clutch calibration is needed (which shouldn't be a big deal), and proper venting, which all sleds need. The biggest issue I believe, is alignment under load. How do you know your alignment is spot on under load? How do you know if it's in spec at rest when the fixed sheave has .024 run-out built in?

Clutched Films · Apr 19, 2018

Jumping ship kinda

This is why I snow checked 2019 Alpha1 & 2019 850 Freeride 137" with shot. I really liked the 850 chassis / power ish but I have to spend time and money just to get it to run with my buddy's 2018 Arctic Cat 800. I think the motor has more power then the Cats she's just losing way to much from crank-track. We road that Alpha1 and it smoked my 850 head to head up the hill and the Alpha1 was still in break in. No messing with clutching & the shocks don't need to be replaced before riding. I'm a diehard Ski-Doo rider or at least was haha. Sad to say but that cat just works better for me with the power & handling on the hill. Can't wait to come back to Ski-Doo once they get it figured out. Still love Doo that's why I got me that 850 Freeride 137" with shot love me that shot haha. You should have seen the disappointment in my father haha.

Adam12 · Apr 19, 2018

Clutched Films said:
This is why I snow checked 2019 Alpha1....

Man, I hope we get some more rides in next year. I wanna see that thing.

apex 9420t · Apr 20, 2018

Wow getting smoked by cats. Something I just haven't seen and I ride with a lot of 18 mtn cats something must be wrong with your 850

bcpowder · Apr 20, 2018

Illinoispowder said:
If engine mounts are the "real" issue, why did the 2017 trail sleds with soft mounts have a much lower failure rate? Proper clutch calibration is needed (which shouldn't be a big deal), and proper venting, which all sleds need. The biggest issue I believe, is alignment under load. How do you know your alignment is spot on under load? How do you know if it's in spec at rest when the fixed sheave has .024 run-out built in?

I think the engine mounts are an attempt to tame the real issue of engine vibration. I don't think the mounts are the "real" issue.

The alignment spec is +/- 1.8mm. .024inches is 0.6mm. with that being said, you can take measurements at a few rotation spots, and take the mean value.

To answer your question about alignment under load, all I can do is ensure the machine is set to spec, with the front dimension being 3mm greater than the rear to accommodate the movement when loaded.

BRP is full of very smart people. If the fix to all their problems was simply an alignment fix under load through motor mounts...it would have been solved last year in the MY2018 Belt life updates. The new mounts for 2019 will be stiffer, and will pull out some more vibration from the belt, but it won't be enough in my opinion.

winter brew · Apr 20, 2018

Here's where I think BRP overthought the whole clutch/belt relationship...
The engineered primary clutch "wobble" to offset engine reciprocation in the up/down axis is a great idea. BUT... The amount of sheave wobble is fixed. The amount of engine movement is variable. ONLY when the engine movement matches the "engineered" amount of movement will the "wobble" work as intended. At ALL other times the primary sheave will be acting similar to excessive crank run-out and basically be scrubbing the belt. This will massively increase temps and shorten belt life.
Even with the proper motor mount hardness, when the belt is under more (or less) tension between the 2 clutches, this will also effect how much up/down movement the engine will see as it pulls on the mounts. Again....varying the relationship between the wobble and engine movement which must be stable and consistent to be effective.
They need to stabilize the engine and eliminate the sheave wobble design unless they can guarantee a consistent amount of engine movement regardless of RPM, engine output, belt tension and motor mount condition. I don't see that as being possible. :face-icon-small-con

Ski-doo#1 · Apr 20, 2018

Well... how come nobody has taken a non-belt blowing sled and observed it head to toe? Why do those sleds work good??

Now I dont know for sure if the larger stroke is the undefeatable issue but if you’re considering a Poo 850 they only increased the stroke as well so vibration will be just as evident. Hopefully the guys who went that route trust the motor mounts they developed.

Daag44 · Apr 20, 2018

Ski-doo#1 said:
Well... how come nobody has taken a non-belt blowing sled and observed it head to toe? Why do those sleds work good??

Now I dont know for sure if the larger stroke is the undefeatable issue but if you’re considering a Poo 850 they only increased the stroke as well so vibration will be just as evident. Hopefully the guys who went that route trust the motor mounts they developed.

Some have and noticed a relationship with the amount of sheave runout, X alignment, Y-X skew, engine movement and the amount of belt squeeze.

clutch · Apr 21, 2018

900 Cats were a long stroke motor and belt problems were not an issue at all on them. I'm sure it has an effect, but it isn't the whole problem by any means.

Matte Murder · Apr 21, 2018

bcpowder
“At the end of the day, if you ride the 2019 850 hard in the mountains, i would predict 200-400 km per belt. The regular rider may be able to get around 1000-2000 km. The disappointing part here is that on the xm, these same riders now getting 1000 - 2000km, used to get 3000 - 5000 km per belt. BRP will isolate the hard riders and rider blame, and eventually you will be on your own with an under performing machine, paying for belts, and dealing with the compounding wear and tear of a constantly overheated and shock loaded crank.”

No way guys were getting good performance out of the XM on belts for 3000-5000kommunist miles(1700-3000miles). A belt is a wear item. Run hard in the mountains anything over 600miles of great performance out of a belt is a gift. I think your expectations are WAY over reality. I had two 2015 XM Trygstad 872 with Roosterbuilt clutching. A 163 and a 174. At 600-700 miles a new belt def gave better performance. I did get lazy on the 174 because I didn’t ride it this year and we actually broke the back out of the belt at what I think was 700-800 miles. That belt gave me all the moneys worth it had!!!

Daag44 · Apr 21, 2018

Matte Murder said:
bcpowder
“At the end of the day, if you ride the 2019 850 hard in the mountains, i would predict 200-400 km per belt. The regular rider may be able to get around 1000-2000 km. The disappointing part here is that on the xm, these same riders now getting 1000 - 2000km, used to get 3000 - 5000 km per belt. BRP will isolate the hard riders and rider blame, and eventually you will be on your own with an under performing machine, paying for belts, and dealing with the compounding wear and tear of a constantly overheated and shock loaded crank.”

No way guys were getting good performance out of the XM on belts for 3000-5000 [kilometers] (1700-3000miles). A belt is a wear item. Run hard in the mountains anything over 600miles of great performance out of a belt is a gift. I think your expectations are WAY over reality. I had two 2015 XM Trygstad 872 with Roosterbuilt clutching. A 163 and a 174. At 600-700 miles a new belt def gave better performance. I did get lazy on the 174 because I didn’t ride it this year and we actually broke the back out of the belt at what I think was 700-800 miles. That belt gave me all the moneys worth it had!!!

I think you meant kilometers. There is no reason to bring senseless politics into sleds, so I made a correction in brackets.

White Rad · Apr 21, 2018

Ski-doo#1 said:
Well... how come nobody has taken a non-belt blowing sled and observed it head to toe? Why do those sleds work good??

Non belt blowing g4? In my experience there is no such thing. You have a bunch of weekend warriors who are average riders and mostly experience average snow conditions claiming that in their 800 miles total this season that their sled is a non belt blower. Bring that sled out here on the right day with the Right snow conditions and let’s use it to punch in the trail and it will eat belts. They all will. But it takes a certain riding style and more importantly certain snow conditions to make the real extent of the belt issues become apparent.

White Rad · Apr 22, 2018

winter brew said:
Here's where I think BRP overthought the whole clutch/belt relationship...
The engineered primary clutch "wobble" to offset engine reciprocation in the up/down axis is a great idea. BUT... The amount of sheave wobble is fixed. The amount of engine movement is variable. ONLY when the engine movement matches the "engineered" amount of movement will the "wobble" work as intended. At ALL other times the primary sheave will be acting similar to excessive crank run-out and basically be scrubbing the belt. This will massively increase temps and shorten belt life.
Even with the proper motor mount hardness, when the belt is under more (or less) tension between the 2 clutches, this will also effect how much up/down movement the engine will see as it pulls on the mounts. Again....varying the relationship between the wobble and engine movement which must be stable and consistent to be effective.
They need to stabilize the engine and eliminate the sheave wobble design unless they can guarantee a consistent amount of engine movement regardless of RPM, engine output, belt tension and motor mount condition. I don't see that as being possible. :face-icon-small-con

This right here is a great description of what’s going on !

Chadly · Apr 22, 2018

White Rad said:
Non belt blowing g4? In my experience there is no such thing. You have a bunch of weekend warriors who are average riders and mostly experience average snow conditions claiming that in their 800 miles total this season that their sled is a non belt blower. Bring that sled out here on the right day with the Right snow conditions and let’s use it to punch in the trail and it will eat belts. They all will. But it takes a certain riding style and more importantly certain snow conditions to make the real extent of the belt issues become apparent.

I didn't blow a single belt this season. Rode multiple times in multiple states with it over the hood deep snow. I have after market clutching and blow holes though.

jvb · Apr 22, 2018

Chadly said:
I didn't blow a single belt this season. Rode multiple times in multiple states with it over the hood deep snow. I have after market clutching and blow holes though.

You also weigh 120 lbs soaking wet! 154s should also be better on belts.

Yella Belly · Apr 22, 2018

2000 miles, and twp belts. The one currently on it, and the one in the clutch cover.
Not even a pulled thread.
I did drill the big hole in the cover, and I did have the gearing changed but saw no issue with belts. ANd the gearing made it much better on the hills. It held RPM, and track speed. Guess I got one of the Wednesday sleds rather than a Monday or Friday pm.

Yella'

850 Belt life - A band aid Journey

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