scooter top speeds. governed?
 

are most scooters governed? ..or is it a limitation of each scooter design...

Normally the CVT is limited so it cannot access the highest ratios.

If a certain washer or two are removed from the cvt, and new rollers installed, the top speed can be increased.

i'm looking at a 150cc honda gyro cvt (:

I've got a fair bit of tuning experience with scooters. And generally your big name brand modern scooters will be rev limited. They often have soft rev limiters that basically cut every third spark to lower power output at redline. And yes often times there is a cvt limiter but that will only limit where you run out of gearing so that at top speed your revs are sky high and trip the rev limiter. Remove those then you get a wider range of gearing and more fuel efficiency. The next step would be to get a new no unlimited CDI or reprogram your ecu if it's a fancy new FI scooter.

As for roller weight unless your too light on the weights, on flat land with no wind, you'll have the same top speed whether you use heavy or light weights. The weights only affect your acceleration and hill climbing ability by keeping the engine in it's powerband for as long as possible. Ideally you want lighter weight rollers so that your rpm stays at the peak power rpm until you hit your drag limited top speed. If the rpms stay sort of low then start climbing after a certain speed then you're too heavy. This really only applies to 50cc scooters. That honda gyro cvt falls into the 50cc tuning category so look for any restricting washers in the cvt and if you want replace it with a high performance cvt with a wider gearing range.

But since this is an ecomodding forum in certain cases you may want your rpms to stay low. If you've got a larger displacement scooter say a 150cc or so and you want maximum fuel effeciency then what you want is heavier weights that keep the rpm low til about 40-45 mph then climb from there, that way putting around gets maximum mpg and as the revs climb to faster speeds you get gradually increasing power without wasted rpm.

Is it a 50cc motor? A lot of scooters are limited by spacers placed in the variator, which limits the range of the CVT and thus the ratios available in the transmission. On my scooter (50cc 2 stroke), there were also restrictors placed in the intake and exhaust that cut down on the amount of air that could flow into and out of the engine. By using a dremel to remove the restrictors, I picked up another 10 mph from the scooter, going from a top speed of 32 to 42 mph.

If you remove restrictors from the engine, though, most times you will have to rejet the carb to keep the engine from running too lean or rich.

I had a 2002 Yamaha BWS scooter. Bought is used. It would do 59 km/h flat out, and got 90mpg. I put new rollers (stock) and belt (Kevlar) in it and the it would do 66 km/h and 100 mpg. Finally, I put an Athena aluminum 70cc cylinder on it and higher final drive gearing. Then it would do 90 km/h, 100 km/h if I was in a full tuck, all with the stock exhaust and close to the same engine revs as stock. And, strangely enough, 120 mpg.

Most "modern" scooters (BWS, Vino, Jazz, Ruckus, etc) are limited by gearing. Once they reach ~ 50 km/h, the CVT is at the fastest ratio. And when it reaches its top speed of 60-70 km/h, depending on the bike, the engine RPM is above the power band and simply can't push anymore. I did try upping my final drive gearing before the 70cc upgrade, and this added about 10 km/h top speed. It did accelerate the same as the CVT took care of that. However, with the 50cc engine it was horrible from a stop. I was scared that I was going to smoke my centrifugal clutch every time I took off. Higher gearing needs 70cc. And you can't gear higher by changing rollers.

The other option is to put an aftermarket exhaust on. It will raise the powerband of the engine, thus raising your top speed. Most pipes come with lighter rollers to tune the CVT for the higher RPM powerband. It is the cheaper option than gearing and 70cc, but higher revs and loud exhaust at top speed would probably just annoy everyone around you.

You can widen the cvt's overall range by installing a larger diameter aftermarket cvt. I use the polini variator on my 50cc chinese scooter and revs at 40 mph dropped from about 8500 down to a managable 7500. You can also get wider range by going to a Dr. Pulley style D-shaped weights. They push the variator drive face out further than round ones at top speed, do this only if you know there is unused drive face on your variator. It's cheaper and easier than trying to change your gearing.

And generally with gear changes you should tune your clutch so you don't burn it out. Lower stall clutches will keep you from burning the clutch out but do need more torque normally achieved with bigger engines. Then with bigger engines you need a stronger torque spring and stronger belt to keep from squishing the belt. This necessitates slightly heavier weights. It's a complicated matter to try and upgrade these small scooters and in general it's far easier to just buy a bigger scooter and change out the weights for efficiency than try to basically rebuild the engine and tranny from the ground up for efficiency.

i'm looking at 150cc honda gyro cvt.
(updating my previous post)

Honda Gyro's r cool...