CVT Eductation (That I Don't Want)

slowhand · 03-09-2022, 09:46 PM

So it seems that I'm about to get a master's degree in scooter CVT transmissions. %$^* it!

My new 150cc scooter tops out at 40 mph & I'm not a happy camper. I'm trying to sort out how to get another 15 mph out of it...

I found the following from an informative webpage:

https://modernvespa.com/forum/wiki-c...to-improve-it-

"One of the biggest misunderstandings is that changes to the variator, clutch and contra springs, and the weight of the rollers will increase your overall power, or top-end speed. This is incorrect, what these changes do are to make the power more useable by allowing the engine to maximize its RPM while it is accelerating, and maximize the speed the engine is revving at when it hits the highest gear ratio available. To optimize the scooter's performance the engine needs to be running at its maximum torque output consistently while accelerating (which on most scooters is somewhere between about 6500-8500 rpm's as this is the level where the 'power band' is at its highest). The whole point of the CVT is to keep the engine at the most efficient RPM by making the gearing variable, the CVT adjusts the gear ratio to maintain that optimum RPMs. Top speed will be achieved when the maximum horsepower hits the limits of drag (friction and air resistance)."

Is it true that the power band in my nifty new 150cc scooter is somewhere between 6500 & 8000 RPM? I'm concerned because my scooter maxes out at 6000 RPM. Which means that my scooter isn't hitting the power band.

Major Bummer.

Or is the point here that my engine's max RPM is being limited to 6000 rpm (out of the power band) by a poor choice of CVT components &/or combination of CVT components by the manufacturer of my nifty new scooter?

I really DON'T want this education.

Thanks all.

TxTaoRider · 03-10-2022, 12:11 AM

I think I'd start by doing some research on your scooter. Somewhere out there you'll find the peak hp and tq along with the rpms they occur at. Then if you discover your engine isn't able to reach the peak hp rpm listed you'll know there's a problem.

Boatguy · 03-10-2022, 03:28 AM

What TxTao said and yes. Most likely it’s the second option in your post.

Your transmission may be bogging down the engine too much and not letting it get to the peak torque/hp area of the RPM curve. Makes a lot of sense based on what you’ve posted in your threads. That would easily explain your low top speed.

Definitely find the rpm torque/hp curves for your particular engine and see where the peaks are. Compare those to 6000 rpm. Se what the difference is.

Is there a way to adjust a CVT to get things right?

Based on your posts and a guess, it seems you’ll want to adjust it in a way that allows it to slip more, reducing the gearing a bit.

Which also makes me think: are these CVTs in an oil bath? If so, are you using the right oil to let is slip enough?

Also is it possible that at 150 miles, the transmission is still breaking in? That whatever the plates or whatever are on there that slip still need to wear down a bit to slip a little better? More wear would mean more slip which would mean lower gearing and higher RPM.

Magician16 · 03-10-2022, 04:36 AM

These cvt's are almost exactly like the clutch drives on a snowmobile. It could be as simple as the alignment of your clutches is off, and there should be some adjustment to the driven clutch to get the ride height of the belt right. The cvt is normally at its optimum setting from the factory for a given elevation. If you're over 5, 000 feet in elevation, you will have a lot of power loss. It's probably not the cvt; I suspect the valves need to be adjusted. Either valves or the carb needs adjusting, probably both. Also, if it's new the engine needs a few hundred miles of break in.

65cabriolet · 03-10-2022, 09:07 AM

The CVT tranny is not that hard to figure out. There is a lot of good info over at 49ccscoot.com on them... don't let the URL fool ya, they do more than the 49cc scooters.

slowhand · 03-11-2022, 10:56 AM

Quote:

Originally Posted by TxTaoRider

I think I'd start by doing some research on your scooter. Somewhere out there you'll find the peak hp and tq along with the rpms they occur at. Then if you discover your engine isn't able to reach the peak hp rpm listed you'll know there's a problem.

Thanks TxTaoRider. The spec page in the owner's manual says: 157QMJ. Is the what I'm looking for? No idea what it means. Must be some variation or version of the generic GY6.

slowhand · 03-11-2022, 11:03 AM

Quote:

Originally Posted by Boatguy

What TxTao said and yes. Most likely it’s the second option in your post.

Your transmission may be bogging down the engine too much and not letting it get to the peak torque/hp area of the RPM curve. Makes a lot of sense based on what you’ve posted in your threads. That would easily explain your low top speed.

Definitely find the rpm torque/hp curves for your particular engine and see where the peaks are. Compare those to 6000 rpm. Se what the difference is.

Is there a way to adjust a CVT to get things right?

Based on your posts and a guess, it seems you’ll want to adjust it in a way that allows it to slip more, reducing the gearing a bit.

Which also makes me think: are these CVTs in an oil bath? If so, are you using the right oil to let is slip enough?

Also is it possible that at 150 miles, the transmission is still breaking in? That whatever the plates or whatever are on there that slip still need to wear down a bit to slip a little better? More wear would mean more slip which would mean lower gearing and higher RPM.

BoatGuy. Thanks for the ideas. I don't believe the trans uses a 'wet' clutch like the manual motorcycles. I think the clutch is a dry clutch without any adjustments in the OEM units. At least that's what I've seen so far regarding available aftermarket clutches. There are a few that have adjustable springs/weights to tune the RPM where the clutch is applied at take off but I don't think this is where the problem is. The bike starts off easily and just about where I'd expect it to using the throttle and accelerates briskly to 40 mph/6000RPM and then just won't go any faster.

I realize that the bike is still new and only has a few miles on it but I doubt as it 'breaks in' that I'll get another 15 MPH out of it. Maybe 2 or 3 more MPH but 15 is a big ask. Also, if the power band really is above 6000 RPM, I have my doubts that as it breaks in it will rev up in the 8000 RPM range. Again, this seems a big ask.

I'll keep it in mind as I fall down this rabbit hole...

slowhand · 03-11-2022, 11:14 AM

Quote:

Originally Posted by Magician16

These cvt's are almost exactly like the clutch drives on a snowmobile. It could be as simple as the alignment of your clutches is off, and there should be some adjustment to the driven clutch to get the ride height of the belt right. The cvt is normally at its optimum setting from the factory for a given elevation. If you're over 5, 000 feet in elevation, you will have a lot of power loss. It's probably not the cvt; I suspect the valves need to be adjusted. Either valves or the carb needs adjusting, probably both. Also, if it's new the engine needs a few hundred miles of break in.

Magician, I'm at 180 feet above sea level here on the gulf coast of Florida. Surprisingly it's not all flat like most of the state. We actually have a few small hills here that add a little scenery to the place. Not the best for 2 wheeled riders but still...

As for adjusting the valves & carb I'll go down this road if I can't find any other culprits. I'm also a little afraid to start adjusting/tuning things until I reach the end of the break in period (500 km according to dealer, 1000 km according to mfgr).

I realize that the engine/bike are still new but I doubt that as/after it 'breaks in' that it'll pick up 15 MPH (> 35% increase) and 2000 RPM (33% increase). This seems like a big ask from a 6 or 8 HP engine.

Thanks for the help.

slowhand · 03-11-2022, 11:18 AM

Quote:

Originally Posted by 65cabriolet

The CVT tranny is not that hard to figure out. There is a lot of good info over at 49ccscoot.com on them... don't let the URL fool ya, they do more than the 49cc scooters.

65cabriolet, Thanks for the idea. I'll continue my education at 49cc scooters for a while. Can't hurt.

slowhand · 03-11-2022, 11:46 AM

Thanks to TxTaoRider I have the following short spec sheet on the engine in my scooter:

157QMJ
Specifications

Style: Short case.
Engine Type: Single Cylinder 4-Stroke.
Cooling: Air Cooled.
Displacement: 149.6cc.
Cylinder: 57.4 mm.
Piston Displacement: 57.8 mm.
Max Power: 5.6 kw/7500 rpm. (7.6 HP)
Max Torque: 7.6 N.m/6000 rpm.

The spec sheets shows 6000 rpm as the max torque for the engine. Based on the wiki page at the start of this thread it seems to indicate that this is just what I want for max performance. This is where max speed should be achieved. At least if that wiki info is correct I think it should.

So if 6000 is the peak of the engine's power band (or torque curve) something's working right. The tach may be off a little but I suspect it's close enough. But at only 40 mph I'm still not a happy camper.

%&*$!

65cabriolet · 03-11-2022, 03:32 PM

Given what you have just said, it's time to get into the CVT. Make sure your drive belt is setup correctly (as far out on the big one and as far in on the little one).

TxTaoRider · 03-11-2022, 07:44 PM

Did you check your mph with a phone or gps?

slowhand · 03-12-2022, 01:33 PM

Quote:

Originally Posted by TxTaoRider

Did you check your mph with a phone or gps?

No, I don't have any way to use GPS speed. I'm going strictly from the speedo.

slowhand · 03-12-2022, 01:36 PM

Add'l info... I just put my 2nd gallon of gas in. I was told that I should expect 80+ mpg. I'm currently at 61 mpg for a 2 tank average. First gallon was 62, the second was 60. What should I expect? is 60 about right (given that the engine isn't broken in yet)? Or is 80 really the correct mark for a NEW 150cc scooter?

Thanks again.

slowhand · 03-12-2022, 01:43 PM

Quote:

Originally Posted by 65cabriolet

Given what you have just said, it's time to get into the CVT. Make sure your drive belt is setup correctly (as far out on the big one and as far in on the little one).

I've kind of resolved myself to opening up the trans case. It's been raining here the last few days so I'm waiting for a break in the weather.

If the belt were slipping I suspect I'd hear a lot of squealing from trans. But I can't hear any signs of belt slippage. I'm wondering if maybe the clutch is slipping. In my truck when the clutch was about shot and it would slip I could see the tach bouncing around as the clutch slipped. But I don't see the tach bouncing around on the scooter. It just climbs in pace with the engine sound until it hits 6K. Then it just stays stuck at 6K.

Thanks. As soon as I can I'll stick my nose into the trans workings. Yuck.

03-09-2022, 09:46 PM	#1
slowhand Join Date: Mar 2022 Posts: 26	CVT Eductation (That I Don't Want) So it seems that I'm about to get a master's degree in scooter CVT transmissions. %$^* it! My new 150cc scooter tops out at 40 mph & I'm not a happy camper. I'm trying to sort out how to get another 15 mph out of it... I found the following from an informative webpage: https://modernvespa.com/forum/wiki-c...to-improve-it- "One of the biggest misunderstandings is that changes to the variator, clutch and contra springs, and the weight of the rollers will increase your overall power, or top-end speed. This is incorrect, what these changes do are to make the power more useable by allowing the engine to maximize its RPM while it is accelerating, and maximize the speed the engine is revving at when it hits the highest gear ratio available. To optimize the scooter's performance the engine needs to be running at its maximum torque output consistently while accelerating (which on most scooters is somewhere between about 6500-8500 rpm's as this is the level where the 'power band' is at its highest). The whole point of the CVT is to keep the engine at the most efficient RPM by making the gearing variable, the CVT adjusts the gear ratio to maintain that optimum RPMs. Top speed will be achieved when the maximum horsepower hits the limits of drag (friction and air resistance)." Is it true that the power band in my nifty new 150cc scooter is somewhere between 6500 & 8000 RPM? I'm concerned because my scooter maxes out at 6000 RPM. Which means that my scooter isn't hitting the power band. Major Bummer. Or is the point here that my engine's max RPM is being limited to 6000 rpm (out of the power band) by a poor choice of CVT components &/or combination of CVT components by the manufacturer of my nifty new scooter? I really DON'T want this education. Thanks all.
	0

03-10-2022, 12:11 AM	#2
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	I think I'd start by doing some research on your scooter. Somewhere out there you'll find the peak hp and tq along with the rpms they occur at. Then if you discover your engine isn't able to reach the peak hp rpm listed you'll know there's a problem. __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
	0

03-10-2022, 03:28 AM	#3
Boatguy Join Date: Feb 2021 Location: Northeast Posts: 929	What TxTao said and yes. Most likely it’s the second option in your post. Your transmission may be bogging down the engine too much and not letting it get to the peak torque/hp area of the RPM curve. Makes a lot of sense based on what you’ve posted in your threads. That would easily explain your low top speed. Definitely find the rpm torque/hp curves for your particular engine and see where the peaks are. Compare those to 6000 rpm. Se what the difference is. Is there a way to adjust a CVT to get things right? Based on your posts and a guess, it seems you’ll want to adjust it in a way that allows it to slip more, reducing the gearing a bit. Which also makes me think: are these CVTs in an oil bath? If so, are you using the right oil to let is slip enough? Also is it possible that at 150 miles, the transmission is still breaking in? That whatever the plates or whatever are on there that slip still need to wear down a bit to slip a little better? More wear would mean more slip which would mean lower gearing and higher RPM. __________________ 2020 Lifan x-pect
	0

03-10-2022, 04:36 AM	#4
Magician16 Join Date: Aug 2019 Posts: 468	These cvt's are almost exactly like the clutch drives on a snowmobile. It could be as simple as the alignment of your clutches is off, and there should be some adjustment to the driven clutch to get the ride height of the belt right. The cvt is normally at its optimum setting from the factory for a given elevation. If you're over 5, 000 feet in elevation, you will have a lot of power loss. It's probably not the cvt; I suspect the valves need to be adjusted. Either valves or the carb needs adjusting, probably both. Also, if it's new the engine needs a few hundred miles of break in. __________________ 2018 Bashan Storm(sold) 2016 Magician 250
	0

03-11-2022, 11:46 AM	#10
slowhand Join Date: Mar 2022 Posts: 26	Thanks to TxTaoRider I have the following short spec sheet on the engine in my scooter: 157QMJ Specifications Style: Short case. Engine Type: Single Cylinder 4-Stroke. Cooling: Air Cooled. Displacement: 149.6cc. Cylinder: 57.4 mm. Piston Displacement: 57.8 mm. Max Power: 5.6 kw/7500 rpm. (7.6 HP) Max Torque: 7.6 N.m/6000 rpm. The spec sheets shows 6000 rpm as the max torque for the engine. Based on the wiki page at the start of this thread it seems to indicate that this is just what I want for max performance. This is where max speed should be achieved. At least if that wiki info is correct I think it should. So if 6000 is the peak of the engine's power band (or torque curve) something's working right. The tach may be off a little but I suspect it's close enough. But at only 40 mph I'm still not a happy camper. %&*$!
	0

03-10-2022, 09:07 AM	#5
65cabriolet Join Date: Feb 2018 Location: Brighton CO Posts: 54	The CVT tranny is not that hard to figure out. There is a lot of good info over at 49ccscoot.com on them... don't let the URL fool ya, they do more than the 49cc scooters.
	1

03-11-2022, 03:32 PM	#11
65cabriolet Join Date: Feb 2018 Location: Brighton CO Posts: 54	Given what you have just said, it's time to get into the CVT. Make sure your drive belt is setup correctly (as far out on the big one and as far in on the little one).
	0

03-11-2022, 07:44 PM	#12
TxTaoRider Join Date: Oct 2020 Location: Flower Mound Texas Posts: 904	Did you check your mph with a phone or gps? __________________ 2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene"
	1

03-12-2022, 01:36 PM	#14
slowhand Join Date: Mar 2022 Posts: 26	Add'l info... I just put my 2nd gallon of gas in. I was told that I should expect 80+ mpg. I'm currently at 61 mpg for a 2 tank average. First gallon was 62, the second was 60. What should I expect? is 60 about right (given that the engine isn't broken in yet)? Or is 80 really the correct mark for a NEW 150cc scooter? Thanks again.
	0