Q. What CVT drive belt does my scooter use?
One of the easiest ways to tell what belt you need is to find out what it has now. Drive belts usually have a part number or a length or both printed on them, though it may get worn off or if the belt snaps it can be difficult to figure out. If you have only a part number, try using your favorite search engine to find the belt or it's specs. If it's a part number from the scooter manufacturer, such as Yamaha or Honda, you should be able to purchase a replacement at a dealership or online parts dealer.
Belt size is most commonly expressed with 3 sets of numbers, 788 17 28 for example. The first number (788 in our example) tells the belt's length in mm. The second (17) is the belt's width in mm. The third (28) expresses the angle of belt's sides. Sometimes an exact match can be difficult to find, but generally you can find something very close. For example you may find a 729-17.7-30 when looking for a 729-18-30. Very small deviations in size will often work fine. If you can't find exactly what you're looking for try to stay within a few mm on the first number, 0.5mm or less variation for the second, and within 2° for the third.
Any time you are using the current belt to decide on a replacement, it's a good idea to make sure the belt appears to fit the CVT well just in case a previous owner or mechanic installed the wrong belt. The belt should be long enough reach or come near the outer edges of the rear pulley while sitting against the drive boss in the front pulley without much slack. It should be wide enough to fit near the outer edges of the pulleys when closed and thin enough to fit or nearly fit in the center of the pulleys when open. The angles should closely match the angles of the drive faces. If any of this seems incorrect, try to verify the correct belt size in other ways as described in this section.
If you have a big name brand, Yamaha for example, you may be able to look up the required belt at a dealer or online parts place. Some scooters will include the required belt part number or size in the owner's manual or you may find it in a service manual. The listing below includes typical sizes for some Chinese scooters. It is still best to check your current belt length if possible, because there are some less common variations of certain engines that use different belts.
Engine Platform |
Case Length & Details |
Common Belt Size |
139QMB/GY6 50 |
Short (8 Bolts in CVT cover) |
669-18-30 |
139QMB/GY6 50 |
Long (10 Bolts in CVT cover) |
729-18-30 |
139QMB/GY6 50 |
QJ Long (Vento, MotoMojo) |
891-17-30 |
139QMB/GY6 50 |
139QMB w/Minarelli 2T Style CVT (QJ1P39QMB-3) |
836-17-30 |
1E40QMB/Minarelli Clone |
Short & Long |
788-17-28 |
1E40QMB/Minarelli Clone |
Adly Long (Stretched version of a short case) |
878-17-28 |
GY6 125-150 |
Short |
743-20-30 |
GY6 125-150 |
Long |
842-20-30 |
You may find belts in many price ranges and brands in your search. No name Chinese belts should be avoided. They tend to be very poor quality and are known to fail prematurely. I have experienced cheap belts breaking in under 10 miles. You could spend much more replacing multiple cheap belts than buying a good one that should last many miles. I prefer Bando belts when available. Gates is another reputable brand. Be aware that there are some Chinese clones of quality belts like Bando. If the belt you are looking at does not match the other belts of the same make and number it may be a knockoff, especially if the price seems too good to be true. You may also find quality replacements from performance parts manufacturers such as Malossi, Polini, Stage6, and the like. If your belt is supplied by the original Japanese or European manufacturer's dealers (Yamaha, Honda, Piaggio, etc...) it should be a good belt that meets original quality.
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