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Discussion Starter · #1 · (Edited)
Hello,

It happened once or twice near the start of the winter season and I was hoping it was just a one off scenario. However, with the ground freeze and winter firmly set it, it's definitely a reoccurring issue.

It only seems to happen on very steep descents; I'll be in 4low(diff lock on or off), riding the engine brake down when it all of a sudden releases and the machine lunges forward, at which point the engine brake either aggressively reengages(which does not sound/feel healthy), or you have to manually brake and slip and get yourself down the hill(as exciting as it sounds).

From what I've found it looks like the engine brake requires engine RPM to be engaged, so what I'm guessing is happening, is that with the frozen winter trails there is not enough traction/friction to give the wheels any resistance whatsoever while descending, which under normal summer conditions, this resistance would keep the engine rev'd. So it's essentially like gliding down a hill on skies, once you get a ways down, your rev's drop right off and the engine brake cuts out.
I've tried to test this theory a bit by giving it a bit of gas to keep the engine rev'd but it's just a messy scenario applying any throttle going down an icy steep hill.

Also, my engine brake still works fine on long, more moderate descents. That's why I'm thinking it may be a limitation of the design with the steep/icy and low rev's cutting it out, or worse, it gets to a point where it's too steep and the engine brake is overloaded and it just releases. I really hope this isn't the case, but will be able to test for sure in the spring once these same steeper hills have no ice.

Is anybody more familiar with the mechanical workings of these engine brakes that could provide any more detail as to why this is happening?

Thanks,

Picture for sake of picture
92994
 

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I think it is as you stated regarding the RPMs, or lack of due to the slick surface your wheels aren’t rolling and creating the necessary RPM.
A similar scenario on my 2016 was when my greaseless sheave was full of dust and not always back-shifting into its lowest ratio. I started noticing the engine braking being very erratic and letting go when it shouldn’t. I thought my one way bearing was failing till I put grease in the sheave and cured the back shifting issues. The engine braking hasn’t missed a lick since. It just couldn’t create the necessary RPMs because the CVT was stuck in high gear.
 
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Discussion Starter · #3 ·
I think it is as you stated regarding the RPMs, or lack of due to the slick surface your wheels aren’t rolling and creating the necessary RPM.
A similar scenario on my 2016 was when my greaseless sheave was full of dust and not always back-shifting into its lowest ratio. I started noticing the engine braking being very erratic and letting go when it shouldn’t. I thought my one way bearing was failing till I put grease in the sheave and cured the back shifting issues. The engine braking hasn’t missed a lick since. It just couldn’t create the necessary RPMs because the CVT was stuck in high gear.
Thanks for the response, just wanting to make sure this doesn't sound like something that is broke or wore out and I should dig into more. I don't think that's the case yet.
 
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An icy descent is a no win situation. If the tires break traction then engine braking isn't going to help. At that point you're just along for the ride. We ran into that in WV in January where we had no braking (engine or disc brakes) and no ability to steer. We just had to hope for the best.
 

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Discussion Starter · #5 · (Edited)
An icy descent is a no win situation. If the tires break traction then engine braking isn't going to help. At that point you're just along for the ride. We ran into that in WV in January where we had no braking (engine or disc brakes) and no ability to steer. We just had to hope for the best.
Yeah no doubt, on one of them when it let go I had to give it more throttle to steer with the 4 wheel drive rather than let the machine slowly turn sideways 😂. The engine brake does help quite a bit though with all 4 wheels having restricted rolling speed, still a much better scenario than free wheeling down regardless of ice. It makes these descents doable as long as you pay attention and keep a straight line, it's too bad it gives out. Without the engine brake it's just slipping and sliding, best to take another route down.
 

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I think you nailed it. The first thing I thought of is the wheels slipping will eliminate the "back pressure" on the engine braking making the transmission think it's running on normal ground.
 

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My GOD can, he has a Yamaha!:cool:
 

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Discussion Starter · #10 ·
Realistically we drive on ice for 5-6months a year up here, just need winter tires. God would have access to the best tires money can buy, I'm sure he would get them studded... he'd have no problem on ice tbh.
 

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Sounds like a hairy situation. I haven't encountered in with the RMAX yet but I've had some other rides where you had to give it gas to engage engine braking. Not fun when going down a steep slick hill.
 

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In my Gen 1 experience on some of the steep sandy/gravelly stuff in my area, I have found I can stay in better control with the engine-braking in High range. It does not want to loose traction and break the tires free as in Low. $.02
 

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Discussion Starter · #13 ·
In my Gen 1 experience on some of the steep sandy/gravelly stuff in my area, I have found I can stay in better control with the engine-braking in High range. It does not want to loose traction and break the tires free as in Low. $.02
Interesting, I'll give High a shot next time I'm out, thanks
 

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Interesting, I'll give High a shot next time I'm out, thanks
But oh yeh you will go a little faster lol!
 

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Discussion Starter · #15 ·
But oh yeh you will go a little faster lol!
Lol I was anticipating this... although it potentially still sounds like a better option than unpredictably free wheeling down. I'm sure people are reading this wondering why not just throttle the actual brake, as soon as you touch it you lock up and start sliding. It's engine brake somewhat regulating your decent or bust lol.
 
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I've seen some bad stuff happen on downill slope and brakes locking up. Engine braking would be best as long as you can keep the wheels from locking up. Otherwise its a good way to get tipsy.
 

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Drive with 2 feet in 4wd.
A little throttle to keep the wheels turning and some brake pedal at the same time. Take the engine brake out of play!!!! Tires turning but not to fast so your in control. That’s how God does it! LOL

High range with engine braking is also nice when it’s long sections that are rough but not super steep. Low range is to much engine brake so you touch the throttle, then to fast back and forth. High range you can just roll along and drink beer! 🍺
 
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We used to encounter this with snowmachines(snowmobiles for the lower 48!) All you should have to do is blip the gas pedal to get rpm up and the brake will engage. You won't be able to crawls down a icy hill in any sxs unless your chained up or studded to the hills.
 

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Discussion Starter · #20 ·
Just to follow up, I did the same hills again with no snow and the machine has the same issue, engine brake seems to get overloaded and release on steep descents. It definitely didn't do it from brand new because I remember being in awe of the machine on the same hills as it slowly rolled me down these very steep hills in 4low.

Overall it still performs well in the mountains with engine braking and climbing, but the engine brake being unreliable definitely subtracts from the overall performance.

Hopefully Yamaha keeps working on it and perfects it. Their attention to overall off-road package in terms of engine brake, diff lock, reliability, etc. is what got me into Yamaha in the first place(Grizzly)... vs some other brands that are just basing their business modo off of producing the highest HP.
 
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