CVT Basics For New Scooter Owners
Jul 19, 2013 23:31:48 GMT -5
90GTVert, katastroff, and 2 more like this
Post by Fox on Jul 19, 2013 23:31:48 GMT -5
CVT stands for Continuously Variable Transmission. It uses weights and a spring to "shift" the gear ratio not unlike how an 18 speed bicycle shifts only it does it with a belt and pulleys rather than a chain and sprockets. The pulleys and belt allow for a smooth transition from the low end to the high end and it's all automatic. No manual shifting required.
To check out the condition of the belt and the rollers you'll need an impact wrench. I use a 12 volt impact to get the variator and clutch nuts off like this one:
search.harborfreight.com/cpisearch/web/search.do?keyword=12+volt+impact&Submit=Go
If the cover hasn't been removed before, it might be stubborn so after you take all the bolts out you have to whack it with a rubber mallet to break the seal. Then it'll come off easily thereafter. If the gasket rips it's okay. Just pull off any loose pieces and install the cover on there. On 50cc scooters you do not have to remove the kick start lever. On 150cc scooters you do.
Remove the 17mm nut with the impact to get to the 6 weights.
There's three little plastic guides the variator slides in and out on. If they break you will have problems.
This shows a variator that was used with broken/missing guides:
This shows one with normal wear:
These pics/videos will help you understand how a CVT (Continuously Variable Transmission) works. In the first video you can see that they have cut the belt cover and installed a piece to keep the starter gear in place. NEVER start a 50cc 139QMB 4 stroke with the cover off unless you have something to hold the gear in place because it can vibrate out and get caught in the spinning drive face and cause damage. Same with the 150cc scooters. The intermediate gear can vibrate out of the crankcase and it'll shear off the variator guide rails rendering the variator useless. I learned that the hard way.
www.youtube.com/watch?v=viWOOvy45wI
This one shows the action of the weights inside the variator:
www.youtube.com/watch?v=3yRskb0BYwE&feature=fvwrel
This pic shows how you can wire the starter clutch up on a 50cc so you can run the engine with the cover off but I just remove the starter bendix and spin the crank counterclockwise with a drill and socket to fire them up. The bendix should wiggle out without removing the variator.
This vid shows an impact wrench in action. There is no substitute for the impact. I got mine at a Harbor freight for $30. Auto parts stores have 'em as does eBay. It's a "12 volt Emergency Impact wrench" It runs off the scooters battery.
www.youtube.com/watch?gl=GB&hl=en-GB&v=36CcufPuDu0
This shows a guy removing and changing the weights in a 150cc. Same procedure pretty much except you don't have to remove the kick lever on your 50cc:
www.youtube.com/watch?v=hyb9NyR-Sjs
The rear pulley is spring loaded. If your belt shreds, pieces can get lodged in between the pulley faces. These must be removed! A strong human can spread the rear pulley halves apart with his/her fingers as shown in this video of a guy changing a 150 cc belt with no tools.
www.youtube.com/watch?v=fBHAM1am-UE
Note: That procedure can only be done on 125/150cc scoots.
To check out the condition of the belt and the rollers you'll need an impact wrench. I use a 12 volt impact to get the variator and clutch nuts off like this one:
search.harborfreight.com/cpisearch/web/search.do?keyword=12+volt+impact&Submit=Go
If the cover hasn't been removed before, it might be stubborn so after you take all the bolts out you have to whack it with a rubber mallet to break the seal. Then it'll come off easily thereafter. If the gasket rips it's okay. Just pull off any loose pieces and install the cover on there. On 50cc scooters you do not have to remove the kick start lever. On 150cc scooters you do.
Remove the 17mm nut with the impact to get to the 6 weights.
There's three little plastic guides the variator slides in and out on. If they break you will have problems.
This shows a variator that was used with broken/missing guides:
This shows one with normal wear:
These pics/videos will help you understand how a CVT (Continuously Variable Transmission) works. In the first video you can see that they have cut the belt cover and installed a piece to keep the starter gear in place. NEVER start a 50cc 139QMB 4 stroke with the cover off unless you have something to hold the gear in place because it can vibrate out and get caught in the spinning drive face and cause damage. Same with the 150cc scooters. The intermediate gear can vibrate out of the crankcase and it'll shear off the variator guide rails rendering the variator useless. I learned that the hard way.
www.youtube.com/watch?v=viWOOvy45wI
This one shows the action of the weights inside the variator:
www.youtube.com/watch?v=3yRskb0BYwE&feature=fvwrel
This pic shows how you can wire the starter clutch up on a 50cc so you can run the engine with the cover off but I just remove the starter bendix and spin the crank counterclockwise with a drill and socket to fire them up. The bendix should wiggle out without removing the variator.
This vid shows an impact wrench in action. There is no substitute for the impact. I got mine at a Harbor freight for $30. Auto parts stores have 'em as does eBay. It's a "12 volt Emergency Impact wrench" It runs off the scooters battery.
www.youtube.com/watch?gl=GB&hl=en-GB&v=36CcufPuDu0
This shows a guy removing and changing the weights in a 150cc. Same procedure pretty much except you don't have to remove the kick lever on your 50cc:
www.youtube.com/watch?v=hyb9NyR-Sjs
The rear pulley is spring loaded. If your belt shreds, pieces can get lodged in between the pulley faces. These must be removed! A strong human can spread the rear pulley halves apart with his/her fingers as shown in this video of a guy changing a 150 cc belt with no tools.
www.youtube.com/watch?v=fBHAM1am-UE
Note: That procedure can only be done on 125/150cc scoots.