I ride a 100cc Yamaha BWS. The engine is in great shape and the bike is perfect. But top speed of about 95 and 100 downhill. I understand it’s only a small scooter so I can’t expect that much. I recently replaced the tranny belt and pully and I fiddeled with the weight rollers to find the best weight/ RPM while accelerating. The bike accelerates much faster and it’s smooth but I barely gained any top speed. I don’t need to go faster but I’d like to reduce the engine noise by reducing RPM for the long drives. Is there any way to do that? I’m not sure there even are different tranny gears available for that bike and I don’t really want to loose too much acceleration anyways as my bike already is not that fast at take offs.
As now I’ve given up trying it seems if I want more leverage, I would have to ride a faster bike.
We’ve got a BWS 100 as well…
The top speed for ours might be 80k with a stiff wind behind you. But put it on an incline and watch that little two stroke go. It was never designed for speed, and no matter how much you fiddle with the tranny weights and other goodies, the bottom line is that the gearing for the transmission and engine torque curve are designed for low end/ mid range grunt. Take it into the mountains more often, and appreciate it’s ability to keep up with larger displacement scooters on steep twisty roads. It’s also not bad on washboard roads and ruts. Drop a few psi out of the tires and you can kind of go nuts in the dirt (for a scooter).
After 6 years and 40,000km it’s been trouble free, other than the husband ripping off the spouses exhaust pipe while playing on a construction site… 
Thanks MJB. I think the pulley or the belt may be old on your bike. If there is a groove on it, the belt will not go past it and the bike just starts reving higher in order to go faster until you hit full throttle at 80km/hr. When you go downhill, there is no pressure on the belt and pulley, yet the same pressure from the weight rollers fed by centrifugal force pushes the belt up past that groove on the pulley and you fell like you just took off. My bike reaches 90 quickly but then from there it’s slow gaining anymore speed. I beleive you also have a faster bike so maybe pointless to spend money to gain only 10km/hr. My wife’s BWS tops at 80 as well but she refuses to spend the money for only 10km/hr. Kinda makes sense. I don’t really want to spend too much on mine either but I was just curious because I know many guys modify their scooters to go faster. I can put on a performance muffler on for 3500nt but I doubt it would even feel different appart from being noisier. Other than that, there’s nothing I can think of.
My SYM Mio 50cc is slow too. My Yamaha 50cc could get up to 70km/h, but the Mio craps out at 60ish. The Mio is quick off the mark and bigger, but the Yamaha was much better getting up speed once over 50km/h.
Dude, you mentioned having changed the belt and rollers in your drive!..do you know what weight your new rollers are?..It’s very common in Taiwan for mechanics to put in lighter rollers for quick acceleration!..this in turn, reduces your top speed! I would suggest throwing in some slightly heavier rollers and give that a shot!..It should improve your top end…and will reduce some of your low speed acceleration though!..don’t go too heavy or else your scooter will become a slug off the line…if you go too light, it will be a cruising slug…so find the weight that’s right for you based on your needs!
Cheers
[quote=“skylarkpuma”]Dude, you mentioned having changed the belt and rollers in your drive!..do you know what weight your new rollers are?..It’s very common in Taiwan for mechanics to put in lighter rollers for quick acceleration!..this in turn, reduces your top speed! I would suggest throwing in some slightly heavier rollers and give that a shot!..It should improve your top end…and will reduce some of your low speed acceleration though!..don’t go too heavy or else your scooter will become a slug off the line…if you go too light, it will be a cruising slug…so find the weight that’s right for you based on your needs!
Cheers[/quote]
Thanks you. But that’s what I meant by fiddling with the weight rollers. I did not find that lighter rollers affected my top end however. It just affected how quick I would get to it. basically, light rollers will accelerate faster but then be slow reaching the last 10 km. The heavy rollers are slow off the start but once you’re going, you reach the top end quicker. The top speed remains the same it seems. I found that mixing three light ones with three heavy ones alternatively works best for smooth acceleration throughout all the way to 90km/hr. But it just won’t go faster… I do the work myself by the way. Until I break something…
P.S. My weights are 6 and 7 grams(3 of each). Stock for my bike is 11 grams.