Cvt vs. Gearbox

roo · Apr 8, 2016

This is a qoute from another thread

" whip that thing
For sure my Yamaha doesn't have the power I would prefer. 75 wide fat horses would be better.

Better than more 4 stroke hp is two stroke power delivery. The four stroke power delivery in any amount is self defeating in any soft traction condition..........read that as snow, is way not good. Right now that just happpens to be all most of us have. 100 hp four stroke bike still sucks as far as power delivery in snow.

Why haven't 4 stroke sleds become kings of the back county,..... no amount of hp or track can fix slogging digging thumping submarine 4 stroke power delivery. We are all fighting the same issue with our thumper bikes.

We need two stroke power with good transmissions . Right now our choice is torqueless motors tooo small or motors toooo old. Sled engines don't have transmissions and cvt transmissions are worse than 4 stroke power..........Hawk proved that.

The engines are out there. The transmissions are on e bay...........so whose going to step to the plate and build a real sno bike engine."
--------------------------------------------------------------------------

MY THOUGHTS
I have been hearing lots of discussions on the mountain about gearbox vs. Cvt. Never being a snowmobiler and entering this sport with a snowbike (bored, cammed and piped 570 ktm with 2moto kit)
I always felt like every time i had to shift gears while climbing it was game over. Now i know a 2moto is not a good example but since that time i have ridden most flavors of snowbike from 250 2 stroke to turbo 4 strokes and i still feel the same.
My 550 fan hawk, 600 ho and 800 ho clutches have been tuned excellent (which is very different than clutching on a sled) and seem far superior to a gearbox.
Am i missing something??????
I would really like to hear some opinions on this subject because i think it is a huge factor in the progression of the sport.
Building a bored and stroked cr500 is not feesible and a turbo 4 stroke just seems like a time bomb. A big single with a secondary gearbox is doable but weight may be a factor.
Big single 2stroke with a cvt??????
Not looking for an argument, just well thought out opinions.
What direction do people want to see this go?

dieselpower · Apr 8, 2016

Perhaps you could start by sharing some ideas of the engines and transmissions on ebay?

roo · Apr 8, 2016

I am also under the impression that this topic may be a split decision.
Some people might just like banging gears, while others prefer just twisting the throttle.

Could it just be all about preference?

roo · Apr 8, 2016

dieselpower said:
Perhaps you could start by sharing some ideas of the engines and transmissions on ebay?

He was talking about performance harley transmissions.

dieselpower · Apr 8, 2016

Waste of time and money those things are HEAVY

Get a rekluse and blast through gears as needed. Fixing the power output and moving to 2 stroke delivery should be plenty.

CATSLEDMAN1 · Apr 9, 2016

yup

to build a better sno bike engine / snowbike a couple of issues need addressed

1. 2 stroke power
2. minimal rotating mass
3 wide torque band and say 80hp would be a good benchmark
4 no foot shift.............so simplest conversion is an electrical shift setup as per some road bikes.

5 and to sell it to the public electric start.

All the technology is out there, it just requires someone with money and resources stepping to the plate and showing the way.

The work and testing has been done to show:

4 strokes have no bussines in the snow
snowmobile drive train drove the snowhawk out of bussiness
450 2 stroke 80hp is old hat engine layout
counter balanced low vibe 2 strokes are doable

come on man.........get after it.

roo said:
This is a qoute from another thread

" whip that thing
For sure my Yamaha doesn't have the power I would prefer. 75 wide fat horses would be better.

Better than more 4 stroke hp is two stroke power delivery. The four stroke power delivery in any amount is self defeating in any soft traction condition..........read that as snow, is way not good. Right now that just happpens to be all most of us have. 100 hp four stroke bike still sucks as far as power delivery in snow.

Why haven't 4 stroke sleds become kings of the back county,..... no amount of hp or track can fix slogging digging thumping submarine 4 stroke power delivery. We are all fighting the same issue with our thumper bikes.

We need two stroke power with good transmissions . Right now our choice is torqueless motors tooo small or motors toooo old. Sled engines don't have transmissions and cvt transmissions are worse than 4 stroke power..........Hawk proved that.

The engines are out there. The transmissions are on e bay...........so whose going to step to the plate and build a real sno bike engine."
--------------------------------------------------------------------------

MY THOUGHTS
I have been hearing lots of discussions on the mountain about gearbox vs. Cvt. Never being a snowmobiler and entering this sport with a snowbike (bored, cammed and piped 570 ktm with 2moto kit)
I always felt like every time i had to shift gears while climbing it was game over. Now i know a 2moto is not a good example but since that time i have ridden most flavors of snowbike from 250 2 stroke to turbo 4 strokes and i still feel the same.
My 550 fan hawk, 600 ho and 800 ho clutches have been tuned excellent (which is very different than clutching on a sled) and seem far superior to a gearbox.
Am i missing something??????
I would really like to hear some opinions on this subject because i think it is a huge factor in the progression of the sport.
Building a bored and stroked cr500 is not feesible and a turbo 4 stroke just seems like a time bomb. A big single with a secondary gearbox is doable but weight may be a factor.
Big single 2stroke with a cvt??????
Not looking for an argument, just well thought out opinions.
What direction do people want to see this go?

byeatts · Apr 9, 2016

roo said:
This is a qoute from another thread

" whip that thing
For sure my Yamaha doesn't have the power I would prefer. 75 wide fat horses would be better.

Better than more 4 stroke hp is two stroke power delivery. The four stroke power delivery in any amount is self defeating in any soft traction condition..........read that as snow, is way not good. Right now that just happpens to be all most of us have. 100 hp four stroke bike still sucks as far as power delivery in snow.

Why haven't 4 stroke sleds become kings of the back county,..... no amount of hp or track can fix slogging digging thumping submarine 4 stroke power delivery. We are all fighting the same issue with our thumper bikes.

We need two stroke power with good transmissions . Right now our choice is torqueless motors tooo small or motors toooo old. Sled engines don't have transmissions and cvt transmissions are worse than 4 stroke power..........Hawk proved that.

The engines are out there. The transmissions are on e bay...........so whose going to step to the plate and build a real sno bike engine."
--------------------------------------------------------------------------

MY THOUGHTS
I have been hearing lots of discussions on the mountain about gearbox vs. Cvt. Never being a snowmobiler and entering this sport with a snowbike (bored, cammed and piped 570 ktm with 2moto kit)
I always felt like every time i had to shift gears while climbing it was game over. Now i know a 2moto is not a good example but since that time i have ridden most flavors of snowbike from 250 2 stroke to turbo 4 strokes and i still feel the same.
My 550 fan hawk, 600 ho and 800 ho clutches have been tuned excellent (which is very different than clutching on a sled) and seem far superior to a gearbox.
Am i missing something??????
I would really like to hear some opinions on this subject because i think it is a huge factor in the progression of the sport.
Building a bored and stroked cr500 is not feesible and a turbo 4 stroke just seems like a time bomb. A big single with a secondary gearbox is doable but weight may be a factor.
Big single 2stroke with a cvt??????
Not looking for an argument, just well thought out opinions.
What direction do people want to see this go?

CVt is not near as efficient as a gearbox, hp is lost through belt scrub, its user friendly however will not get as much hp to the skid.A cvt loses 10% efficiency unless its at a 1-1 shift ratio , And your only at 1-1 at a certain given speed.

Sheetmetalfab · Apr 9, 2016

byeatts said:
CVt is not near as efficient as a gearbox, hp is lost through belt scrub, its user friendly however will not get as much hp to the skid.A cvt loses 10% efficiency unless its at a 1-1 shift ratio , And your only at 1-1 at a certain given speed.

And while shifting you are always at peak power/tq no matter the trackspeed?

Cvt = peak power at all trackspeeds, and the ability to recover trackspeed rapidly after tight obstacles. (When calibrated)

The cvt on my axys is at 1-1.15 at 54mph trackspeed.
In other terms WFO in deep snow.
Spinning a 163x3 track, often barely making headway.........

If you data log the amount of time the cvt is <80-85% power (and who cares about the efficiency) is going to far outweigh the momentum lost in split second shifts of the gearbox.
Not to mention rev limiter, downshift(engine brake then spin/trench) and the amount of time spent out of the peak power/TQ range......<<this is big.......

Probably closer to 80-85% when on dirt with free spinning wheels....
But on snow......

I think reducing the centrifugal force of the spinning clutches is probably the next place for cvt advancement.
Proper placement of the centrifugal mass (J&L snowhawk is the closest) is the best way to take advantage of the greater performance and minimize the handling effects.

Hawkster · Apr 9, 2016

Polaris and Ski-doo have clutches that have a needle bearing sheeve on the primary . Allowing the belt to be snug at idle . Ski -doo uses it on their E-Drive and I'm not sure if they are using it on their new clutch on the 850 ? Polaris uses it on their quads . Engagement is extremely smooth and the belt is suppose to be taunt all the way threw the curve .

CATSLEDMAN1 · Apr 10, 2016

cvt issues

the only knock on cvt for the bikes is the huge increase in rotating mass that produces the gyroscopic affects you feel when trying to throw around a light sled or hawk.

the minute you ditch the 8000 rpm spinning clutch's on a sled, the sled feels 100 lbs lighter. when spinning clutch's were tried on mx bikes, fast as all get out, but wow, you couldn't talk to that thing in the first corner, one blip of throttle and it was straight up.

hawks are not necessarily heavy, they just have the spinning clutch's heavy feel and that dogged their purchase by bike riders. When TS slapped a sled track on a bike, no power runaway, but it was way more playful than hawks & sleds. The number of kits sold now has shown what the public wants, nimble machines. Tanks are out..........well no one buys them.

For now another 5hp on a newer 450 is good, deeper tracks have been a big help, more suspension, more brands. As a lot of us dream and look ahead though, the next stroke is a more appropriate bike/motor transmission donor. The hp we need would be death defying in the dirt, so no one is going to build a better snowbike that sells to dirt bikers.

byeatts · Apr 10, 2016

CATSLEDMAN1 said:
the only knock on cvt for the bikes is the huge increase in rotating mass that produces the gyroscopic affects you feel when trying to throw around a light sled or hawk.

the minute you ditch the 8000 rpm spinning clutch's on a sled, the sled feels 100 lbs lighter. when spinning clutch's were tried on mx bikes, fast as all get out, but wow, you couldn't talk to that thing in the first corner, one blip of throttle and it was straight up.

hawks are not necessarily heavy, they just have the spinning clutch's heavy feel and that dogged their purchase by bike riders. When TS slapped a sled track on a bike, no power runaway, but it was way more playful than hawks & sleds. The number of kits sold now has shown what the public wants, nimble machines. Tanks are out..........well no one buys them.

For now another 5hp on a newer 450 is good, deeper tracks have been a big help, more suspension, more brands. As a lot of us dream and look ahead though, the next stroke is a more appropriate bike/motor transmission donor. The hp we need would be death defying in the dirt, so no one is going to build a better snowbike that sells to dirt bikers.

The 600 hawks were very heavy and weighed in same as a 600 newer sled, also the cvt itself is well over 20 lbs. not saying its bad just giving some facts.I had a Hawk, huge ergonomic mistake IMO.

Hawkster · Apr 10, 2016

I ran the power block for a while before giving into pure pressure and put a TRA on the 600 . I noticed the gyroscopic affect right off the bat .

I eventually went back to the power block after eating two TRAs' with the implanted 800 , the revs was noticeable as soon as the throttle is touched . It raps more like a two stroke bike , not a two stroke sled that has a slower rev with some clutches on the end of the crank . I had to put a starter ring gear on it to slow it down because the revs seemed a bit to fast and spooky . It spooled up like it had no clutch on.

Note : the 800s' only came with a TRA

Also rode one with a P85 and it has the same result as the TRAs' .

The acceleration of these three clutches felt pretty much the same in trying to twist the machine but when letting off of the throttle is a different story. The TRA and P85 had the same response and the machine wanted to drift noticeable to the left . Only thing that seems to make sense is that those two clutches fling more mass outward twisting the machine to the right and than wanting to fall back on deceleration .

Not only does it appear that the gyroscopic happen around the rotation of the clutch but the whole machine and some CVTs' worse than others .

I don't think I would of ever paid any attention to this on a sled since it has a pair of skis to compensate for balance .

A CVT like the power block could be a good application . It keeps it's pucks centralized , no pins , weights or rollers to fling , and slides along the clutch shaft .

What kind of weight would some sort of automatic or manual shift on the bar be ?

J&L Snowhawk · Apr 11, 2016

Gyros

I might be a bit biased here loving the hawk and now my sno-rkt build but I actually feel that the gyro effects are a bit of a good thing. Honestly I don't think it's very noticeable as far as making my bike feel heavy at all. Only 5 days on the 800 since building but I can surly rip the woods as fast as my friends and if leading maybe leave them behind. But guaranteed I'm having a bigger grin on my face the whole time. As far as drifting and doing super hard full throttle **** hooks that's where the gyros help bring machine up

Next winter I should have few more running and get more people to ride them and give feedback.
I'm after a pure adrenalin rush when riding my toys wheather it's ripping endless wheelies on SM bike or crazy lines on snow so hp is king!!

roo · Apr 11, 2016

CATSLEDMAN1 said:
the only knock on cvt for the bikes is the huge increase in rotating mass that produces the gyroscopic affects you feel when trying to throw around a light sled or hawk.

the minute you ditch the 8000 rpm spinning clutch's on a sled, the sled feels 100 lbs lighter. when spinning clutch's were tried on mx bikes, fast as all get out, but wow, you couldn't talk to that thing in the first corner, one blip of throttle and it was straight up.

hawks are not necessarily heavy, they just have the spinning clutch's heavy feel and that dogged their purchase by bike riders. When TS slapped a sled track on a bike, no power runaway, but it was way more playful than hawks & sleds. The number of kits sold now has shown what the public wants, nimble machines. Tanks are out..........well no one buys them.

For now another 5hp on a newer 450 is good, deeper tracks have been a big help, more suspension, more brands. As a lot of us dream and look ahead though, the next stroke is a more appropriate bike/motor transmission donor. The hp we need would be death defying in the dirt, so no one is going to build a better snowbike that sells to dirt bikers.

Hawks are HEAVY! My 800 with a bunch of lightweight parts comes in at 442# without fuel, which is lighter than the stock 600 hawk dry, the stock 503 fanner was just over 400#. I love the machines but they are pigs!

As for rotating mass, yes it is a problem.
The setup i am have run on 600 ho (i wont run this on the 800 due to the increased hp., everything else has been run hard in the 600 for many years without any issues) doo claims 118 hp out of the 600 h.o.

Primary trans
Drive- PB50=8.6#
driven- stock doo (2005 rev)=8.8#
Primary belt=1.4#
Total=18.8#

Secondary trans
7075 alum jackshaft=2.2#
Belt=.66#
Upper pulley=1.08#
Lower pulley=2.5#
Ideler=.65#
Total=7.09#
Drive train up to the drive shaft total=25.8#

You could cut this weight down a little but not much. Lighter driven clutch and belt drive?

That is definatly a lot of weight to contend with but do the pros outweigh the cons?
Quote
clutch's were tried on mx bikes, fast as all get out, but wow, you couldn't talk to that thing in the first corner, one blip of throttle and it was straight up. Quote

Is this a good example for a snowbike? I wonder if the effect will be as bad in the snow? And if it would be a sacrifice some would be willing to deal with to get good power delivery. To my knowledge no one has built a lightweight bike with a cvt (under 325#, 100ish hp)
Sounds like a good project!

eric82930 · Apr 11, 2016

I think the pros and cons of both are obvious by now and the customer needs to decide what they want based on the data.

The cvt will be better for straight up climbing and drag racing excpecially on a motor with a narrow powerband or someone with less clutch/shifting experience.

With a broad power band, the gear box will be almost as good with a skilled rider and feel more fun and nimble.

The gearbox never worked on a sled because sleds actually have very narrow power and the older ones couldn't do the infinate side hill through trees like a bike. They usually have to go straight up or go back down.

I prefer the gearbox because of the fun factor. I ride for fun and going straight up is not as much fun as sidehilling. Drag racing is probably the most boring thing you can do on a snowbike.

Interesting thing I noticed about powerbands. I prefer 2 strokes but have owned ever size 2 and 4. The 450s work pretty well soley becasue the power is so wide it matches well with a close ratio gearbox. But they are hard to start in zero degrees and are way too loud. The KX500 power for reference is bigger but so much narrower it doesn't give you much advantage unless you can port it and get it to 70hp so you can power your way into the next higher gear. The 450's rev so high they don't need to grab the next higher gear to have the same track speed as a more powerful 2 stroke that has to upshift because it can't rev. A cvt would erase this problem and true HP would be all that mattered. A kx500 with an 8 speed close ratio would be better but then you would probably be shifting
too much. The vibration on the KX was the reason I retired it.

I have since been content on riding smaller 2 strokes and just having fun matching my climb angle to what ever the fastest gear I can pull. I ride my 250sx like a 125. The hydro clutch is so good I can make it act like a cvt and just lightly slip it for 5 seconds in a higher gear until the ground speed catches up to the engine rpm. This is what pro mx guys used to do the whole race in the glory days of 2 stokes. Thats why they have quick access clutch covers.

SEOINAGE · Apr 11, 2016

CATSLEDMAN1 said:
to build a better sno bike engine / snowbike a couple of issues need addressed

1. 2 stroke power
2. minimal rotating mass
3 wide torque band and say 80hp would be a good benchmark
4 no foot shift.............so simplest conversion is an electrical shift setup as per some road bikes.

5 and to sell it to the public electric start.

All the technology is out there, it just requires someone with money and resources stepping to the plate and showing the way.

The work and testing has been done to show:

4 strokes have no bussines in the snow
snowmobile drive train drove the snowhawk out of bussiness
450 2 stroke 80hp is old hat engine layout
counter balanced low vibe 2 strokes are doable

come on man.........get after it.

I'm with you on this one, gear shift control on the bars is easily doable, could even mod a current kit on the market to work with a cr500 to prove it.

Being that we are dealing with bikes, and the weight is a big factor in what sets them apart. We need to have maximal efficiency, hence why a cvt won't work in that regards either.

So a single with gears would be ideal. A well set up 650cc single two stroke could be light weight and efficient, and make an ideal candidate. Easily surpass 100 hp.

SEOINAGE · Apr 11, 2016

eric82930 said:
I think the pros and cons of both are obvious by now and the customer needs to decide what they want based on the data.

The cvt will be better for straight up climbing and drag racing excpecially on a motor with a narrow powerband or someone with less clutch/shifting experience.

With a broad power band, the gear box will be almost as good with a skilled rider and feel more fun and nimble.

The gearbox never worked on a sled because sleds actually have very narrow power and the older ones couldn't do the infinate side hill through trees like a bike. They usually have to go straight up or go back down.

I prefer the gearbox because of the fun factor. I ride for fun and going straight up is not as much fun as sidehilling. Drag racing is probably the most boring thing you can do on a snowbike.

Interesting thing I noticed about powerbands. I prefer 2 strokes but have owned ever size 2 and 4. The 450s work pretty well soley becasue the power is so wide it matches well with a close ratio gearbox. But they are hard to start in zero degrees and are way too loud. The KX500 power for reference is bigger but so much narrower it doesn't give you much advantage unless you can port it and get it to 70hp so you can power your way into the next higher gear. The 450's rev so high they don't need to grab the next higher gear to have the same track speed as a more powerful 2 stroke that has to upshift because it can't rev. A cvt would erase this problem and true HP would be all that mattered. A kx500 with an 8 speed close ratio would be better but then you would probably be shifting
too much. The vibration on the KX was the reason I retired it.

I have since been content on riding smaller 2 strokes and just having fun matching my climb angle to what ever the fastest gear I can pull. I ride my 250sx like a 125. The hydro clutch is so good I can make it act like a cvt and just lightly slip it for 5 seconds in a higher gear until the ground speed catches up to the engine rpm. This is what pro mx guys used to do the whole race in the glory days of 2 stokes. Thats why they have quick access clutch covers.

Haha, yeah, reason they changed clutches every race or two.

capulin overdrive · Apr 11, 2016

Clutch abuse is half the fun on a 2 stroke!

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Cvt vs. Gearbox

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