Gear box vs cvt

I love shifting gears on the dirt/snowbike. It is where a lot of the fun of riding them is at for me.

In just seeing what needs to happen with all the primary and secondary clutch-systems that had/have gone from snowmobiles to ATV's, between the power loss and the addition of the size and weight, I think that to adapt it to a dirtbike would be a monumental-feat of engineering. In a way, it is why the Recluse has both made it to market and has solved a problem of one needing to be adept at clutching in low-speed situations. Recluse has enabled bikes to be semi-automatics.

I'll admit, though, when I ride a buddies Can Am 650 Outlander with an auto/CVT, and I have also ridden another buddies' Polaris ATV's with auto-trans, and they were fun to ride without needing to shift at all.

I can't help but to think of the old saying, "There is light, strong and inexpensive(cheap). You can choose only two."

As auto-transmissions in vehicles have gotten so much better and can both shift faster than even the very best drivers can shift, and be more intuitive-be programmed to be in the correct gear, every time, no matter the situation, that tech has not come down to 2-wheelers, probably due to the space and weight constraints of the platform(s). In a vehicle, while shifting is fun, as soon as the first traffic jam comes up, it is now annoying to me to have to clutch and shift and I don't mind "D" -for Dump anymore. Even in sports cars, I'd now prefer an automatic over that third pedal and right hand shifter.

I want to keep the gears, the clutch and shifting in the dirtbike/snowbike though. Thankfully I'm not losing anything in between shifts on my bike and kit. If anything, my bike is putting more power to the ground/snow- than I need and it spins up the track and I lose traction. As was/is written in the Camso Owners Manual, something like "The slower one travels, generally, the better the traction." At the same time, guys are fabbing up turbo's and N02 kits as those guys need/want more power, and perhaps, at altitude, they sure do. Here in the lowlands of New England, we don't have to worry about that power-suck at all.

No way in h#ll do I want a heavy, ineficient CVT on my bike

A manual transmission has 97% efficiency, a belt driven CVT has 88. A CVT torroidal has 93%.

Bikes have a transmission because they need it. Don't have the power to waste on cvt

people who talk about power loss are out to lunch. when you have a cvt you can tune the engine to have way more power at a much smaller power band and the cvt will keep you at that rpm all the time. will easily make up for power losses. i can understand for trail riding banging gears is fun. but if you ride deep and techincal a cvt would get you way more places with alot less effort

My bikes

I'm building these with 800 skidoo motor. Super exhilarating to rip and still ride super technical terrain with stock bikes

trikerider said:

A manual transmission has 97% efficiency, a belt driven CVT has 88. A CVT torroidal has 93%.

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So about 14 kw is lost in heat on a snowmobile cvt. That can explain alot of belt problems.

kind of reminds me why I sold all my 4 strokes. They would get me to more places with less effort but I just didn't have as much fun. The most fun by far was a bone stock 250sx 2 stroke and a short track.

I also want to mention for those who have not owned a ktm with hydraulic clutch, it is in no way considered much effort to pull the lever and you can slip the shiz out of it in deep snow with one finger to keep the engine on the pipe. Any kid on an 85 can show you how it's done. I have learned to use the clutch to the point of feeling like it should catch on fire and my steel plates are always blue. They still seem to last forever and new plates are way cheaper than a belt and easy to change. The oil will get dirty quicker but that's cheap too.

If I was building a competition hill climber or a snowbike to drive to work It would have a cvt and a cup holder in place of the clutch lever..... Obviously my vote is I hope the industry does not start building them with a cvt.

There are ways to have a geared CVT that has no constant friction components.

I think it would be interesting to try a dual clutch transmission in a snowbike. Like the Honda Africa Twin 1000 engine.

For the current version(s) of snowbike....I think the current trans/clutch setup is best. Simple, tough, no need to screw with clutching, easy to sort gearing, etc. No one ever wanted a CVT in a dirt bike....unless they didn't know how to ride, I guess.

Economics

I believe the transmission is more economical I’m personally tired of 200$ belts and clutch rebuilding for that reason I believe a snow bike is cheaper to ride which is a whole Nother topic. On the most part I’m only running two gears anyway which isn’t that much shifting

Probably the best solution is to have a bike gear box that is tuned for snow. A good and low first, second that is a little taller and a third with a little overlap, forth is probably fine on most bikes as is. Finally a fifth that is supper tall for the high speed trail. Six gear are cool but if properly spaced it would be Overkill. Someone needs to build engines specifically for snow bikes.

mrsnow said:

On the most part I’m only running two gears anyway which isn’t that much shifting

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What he said... I use one gear most of the time when riding in deep snow. 4 stroke bottem end makes this possible. 2 stroke might be a different story.

dhdey said:

people who talk about power loss are out to lunch. when you have a cvt you can tune the engine to have way more power at a much smaller power band and the cvt will keep you at that rpm all the time. will easily make up for power losses. i can understand for trail riding banging gears is fun. but if you ride deep and techincal a cvt would get you way more places with alot less effort

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Ding ding we have a winner.

A CVT would be easier for riding dirt as well...but no half decent dirt bike rider has ever asked for one/needed one. You can throw all the parts and tricks at something you want....sooner or later you just gotta put in the hours to ride better

J&L Snowhawk said:

I'm building these with 800 skidoo motor. Super exhilarating to rip and still ride super technical terrain with stock bikes

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This setup is the one that I had been thinking about. I assume that the tunnel is fixed to the bike so the track shocks are all of the suspension that you. All you need too in my opinion. Is the final drive on the right side? I assume it is. Is it a belt drive or chain? Is the brake on the right as well? The build is very sanitary. Are you planning on building them for sale to the public?

gears or rubber

the downside to all current CVT transmissions is the killing gyroscopic affect of two big spinning cluth's that you can't argue with. If you put a ten speed transmission with air shift in your new whoopzx 850 skidoo you would never dick with flyweights rubber belts again.

when ROKON built their MX bike with CVT clutch's 30 years ago it was the fastest into the 1st corner hands down, then no human was strong enough to bend it through a corner under power when the clutch' spooled, one sat at a local dealership for 5 years or so, looked great, good pieces and parts, but one ride, wow was it fast and boy oh boy it couldn't turn under power.

So you have to ask your self, why did all the Snow Hawk riders with 150hp motors and cvt clutch's drift off and buy snowbikes ?

I agree with gyroscopic forces.
But as with all forces, gyroscopic forces also cancel each other out if they are opposing forces.
What if we run the engine backwards with high rpm and power and then use reversing step down gear coupled with scaled down cvt.
At least some gyroscopic forces would cancel out. Maybe to the point where they are smaller than refular 450cc motor/gear combo produces.

Same effect with yammi 4cyl and 3cyl. 3cyl is lighter, but 4cyl runs backwards through reversing stepdown gear. 4cyl is easier to throw around because cancelling gyroforces.