I hate to be this guy.. I'm sure it would affect performance, a very little... but maybe try a 900R. They are virtually silent in stock form.

 

I think it is important to note that many including yourself prefer the 900R. I personally do not enjoy the sound of a 900R nor find it any less bothersome to my ear. In fact, I dislike the sound/pitch of all high powered four stroke sleds, although I may change my mind with enough riding.

My first transition from 2S to 4S was with MX (Motor Cross) from a YZ to YZF. It took some coaxing, but I now much prefer the powerband of a the YZF four stroke. I find the lower pitch of the YZF slightly annoying, but not nearly as bad as with sleds having what I believe to be a higher average rpm compared to bikes, and the power band seems so much better. What they have done with the four stroke MX is remarkable.

With hedge trimmers I transitioned fully to four strokes in ~2014, but they are really quiet! And I do not need much power for hedge trimming. A few months ago I had to use a two stroke hedge trimmer for an hour and the zing-zing-zing was getting on my nerves. For saws, like most people I remain with two strokes.

For specifically snowmobiles, I live near a trail and I can hear the four strokes long before the two strokes even with a can. It is like hearing growling from far away. I noticed this phenomenon in the early to mid 2000s as the Yamaha four strokes had become more popular. Most locals believed that I was making this up, so I looked it up and indeed the low-frequency sounds generally travel further than high-frequency sounds.


Hearing Protection

I have kept my hearing, but that is thanks to folks like yourselves on this forum who promote hearing protection. My first influence came around 2000 from am older gentlemen working next to me with a hearing aid. The number of times that he told me to protect my ears was like a broken record. It was several years of being reminded to keep the noise low and wear ear protection when needed. I still do not wear ear protection when mowing the lawn, but because of him I operate the mower at half speed.

Every time I hit/wack a piece of metal such as to break loose a brake drum, I wear ear protection. I only wear muffs, but that seems to work.

I have not yet done anything for snowmobiles, but you guys are having me think about it. However, I am more focused on the mechanics and do not ride much. When I do ride, the average rpm and speed is usually low. Hence, regardless of two or four strokes, the effect sound is kept low.

 

Some loss is okey. I have owned a 900 turbo flashed 190. Did 12000km. It's a bit loud too. My new sled is 2024 BC 154.

900na is quite but soo weak should have at least 125hp.

I know this mint not be possible without brp engineers around, we're are you?? 🤗 sure lurking around in this forum

 

Some loss is okey. I have owned a 900 turbo flashed 190. Did 12000km. It's a bit loud too. My new sled is 2024 BC 154.

900na is quite but soo weak should have at least 125hp.

I know this might not be possible without brp engineers around, we're are you?? 🤗 sure lurking around in this forum

What I learnt from DooTalk with my own experience and my local group, there is a distinct difference in the 2S performance that appeals to maybe half of the riders. Half is a number I made up which is probably closer to a quarter or an even an eight. This is mainly due to the CVT that keeps two strokes attractive.

The low-frequency sound from a 900 or any high performance four stroke does not appeal to everyone including myself, so that is a real thing. BRP are around, but unfortunately not for answering individual questions. They did so on DooTalk in 2005, but it quickly got complicated.


Muffler Design

The muffler design to keep the noise low is in three parts. In the center there are the three perorated pipes with sound detonating material to absorb the noise. Then there are the top and lower chambers to allow the sound to bounce around and cancel each other out as much as possible. The exhaust is first channelled into the first perforated pipe towards the bottom chamber, then up to a second perforated pipe to reach the upper chamber. From there it goes back down a third perforated pipe that we see in your picture before exiting the muffler.

 

^^^^
I second that on the 900TR.

I have never seen any inserts for the 850 mufflers, all I could say is you could try making one yourself and see what happens to your clutching and see if you could compensate by adjusting the clickers.

 

Well. There is 2 tempsensors as you know. They should trigger temp warning before failure..... maybe 🫣

 

Wouldn't it be easier to look at this from the ear side? A set of Bose quiet comfort ear buds work excellent, can be used for several applications, and are reasonably priced.

 

I would look into a few different helmets as well as hearing protection. I also have tinnitus, and it gets worse after being exposed to loud noise. I cannot hear certain higher pitched tones. I can never hear crickets at night nor my wife talking LOL. Anyways, I think getting the maximum ear protection is a better alternative as mentioned above.

 

I hear you. I have helmet with earbuds installed (I install my self) plus ear plugs, double protection. The sound inside my head is then not loud. But still loud enough to trigger higher tinnitus at night when time to sleep making falling a sleep harder, even with masking sound. It is what it is.

But I will never quit snowmobiling! 😂🛝

 

I will check oute the Bose quiet comfort ear buds. Thanks for the tip 🙏

 

Anything to quiet the noise from within the helmet is a great idea.

There is a certain rpm/load range (upper midrange) that brings the ETGs really hot, over 700C (1,292F). In comparison, 800C (1,4702F) EGT is an overheat that trips an all out protect the engine mode, much like 100C (212F) for the Coolant Temp and 85C (185F) ECM Temp.

If my own observations on an 850 are correct, 700C EGT is similar to 60C (140F) Coolant Temp where the ECM begins to regulate temps with a limited margin for corrections, and there may be a variance with elevation. I believe (not verified) the second/middle protection happens at 750C (1,382F) EGT and 85C (185F) Coolant Temp. I do not remember where I got these numbers, so they may be invalid. We would need a bench test to figure the precise corrections programmed by BRP, but this is close enough for me. If I am not mistaken, these values apply to all three manufacturers, Ski-Doo, Polaris and Arctic Cat.

The key point is to keep the two strokes running as cool as possible and staying away from a sustained temperature significantly over 700C EGT and 60C Coolant Temp. In other words, it will easily survive hotter, but the effects are compounded. A good example is a 600R E-TEC cruising at 70 to 75 mph for a long enough period to generate enough heat for the ECM to begin applying a protection with a noticeable performance loss. What that means is we can easily ride at those speeds, but we should avoid sustaining those hotter EGT cruising speeds.

 

Everybody is different, I rode 2strokes for 40 years then 4 strokes for almost 20. I tried a new 2025 mxz xrs 600r last year and enjoyed it. But for me it was noisey, hard on fuel in canada, vibrated more and was a bit jumpy at slower speeds,imho. Back on a 2026 renegade xrs 900 turbo r. Quieter,smoother and better on fuel at Canada trail speeds. Perhaps not better but better for me. P.S. I kept the 600R for my Vermont ride on the tighter trails. Enjoy

 

What if the clutching on the two stroke was better suited to your riding style? Do you believe it would have changed anything?

 

All you guys that posted know more than me for sure I’m just giving my condolences that you can’t ride or enjoy a greasy triple. All jokes aside I hope you figure something out

 

I manufacture a prototype most for fun. 2inch OD. perforated 47mm ID. 200mm long (chamber is 410mm deep). Thin layer of sound insulation, ends were outlet perforation begins at 130mm in.

testing at idle engine temp at 45c, stone floor, standing same place each time, holding phone same height.

Without insert 72.8db, 1min average
With insert 72.5db, 1min average

Say 3% less perceived loudness at idle. How will it dampen sound at higher rpm? More/less?

3% is not so much. Maybe not worth it vs. risk of engine failure. Outlet is 55mm down to 47mm is 17% less area. But this design is not intrusive should flow good still.

I will field test it for a while this winter, with and whitout and see how it works. I will report back. Small fun project 😂🫣

 

@nm9stheham, are you seeing this?

I got into this offline with another owner/member during the past Winter of 2025, but this topic is reaching an interesting level.

Think if it this way. There are people on DooTalk willing to expand their understanding and share their thoughts online. I think the testing will ideally include backpressure, but it is not a realistic for me to ask.

In any case, I believe this is an ideal opportunity to get into the sound detonation aspect of the muffler. I don't think we ever really broached this subject. I wrote about it in February or March of 2025, but never since. I do not remember what topic I wrote it in, but I typically write everything of worth in the 1000 Downfall thread. In any case, I remember it by heart, so I can write it up off the top of my head.

 

@jw1978swede, I do not know what you guys eat in Sweden, but it seems to work. Thank you for sharing your thoughts!

I personally believe that you are threading water with the attempt to lower the noise from the muffler. For the attempt and posting on an open/public forum, I give you a ten out of ten. That takes balls.

The effort to lower the sound volume is for me one of the most interesting subjects.

In the past decade, I have been focusing on lowering the heat mainly from the CVT with proper clutch/belt alignment. The next step was with adequate Air/Fuel ratio for proper running sleds. It does not matter if it is a Carb or SDI or E-TEC. As long as they run correctly, then they are all good.

In recent years, the focus to lower the noise level on DooTalk has been with converting to four strokes. I have been transparent on DooTalk that noise level is not worth the choice between two versus four strokes. There are better ways to solve this problem, mainly with ear plugs.

What really counts, in my opinion, is the rpm. If someone rides low speeds like me, then the easiest way to lower the exhaust sound is by adapting a lower rpm with appropriate gearing, and adding a clutch setup to get both lower engagement and better backshift. That is where @Dynamo^Joe really shines. He may despise me personally, but he remains the smartest person I know for clutching. You only need to tell him what sled you got and the goal.

 

Hearing Aids

I do not have hearing problems, but in the late 1990s I was taught by a gentlemen having hearing aids how to avoid going down his road. He spent four years of repetition to make sure that I understood his lessons. We are over 25 years later and I have kept my hearing. To this day I can still hear the faintest hiss from a leak in the head o-rings.

Today I was wearing earmuffs for trimming. I wear them everyday. If I am about to smack a brake rotor to get it loose, I first put on my earmuffs. Anything that is pounding metal on metal, I wear those earmuffs. Both my knee pads and earmuffs are my most used everyday tools.

One of the only tools that I do not use earmuffs is for my lawn mowing tractor. Out of everyone I know, I am the only person who mows their lawn at half throttle speed. I do this to keep the noise down. I also operate my trimmer at lower speeds for the same reason, although I am always wearing earmuffs.

When I see someone like yourself being concerned with tinnitus, I hope you relate that I am concerned with the same thing on a daily basis. It reaches the point that if I need to hit a metal punch, I am wearing the earmuffs.

Your topic has me rethink the ear protection that I need while riding snowmobiles. I prefer riding without ear plugs, but you have given me reason to consider it. Much like with mowing my lawn, I do keep the noise level down with lower rpm.