How can roller weights increase top speed?

[wolfbat3]

alright i am confused except for my ignition coil and cdi my 50cc scoot is stock and i get it up to 37.6mph on straight aways. not to fast on take off but it gets out of the quick enough.

[vvtr]

depends if the engine is revving out proper.
with stock gearing the only way it will go faster is to get more rpm.
a mate's kymco agility was like this... turned out all that was wrong was it was a bit lean in the mid throttle.
cured by adding a washer under the needle (no clip to adjust!)
naraku do reasonably priced gear up kits for the 139qmb - i got a +10% set for my baotian and it pulls 60+ on a good road, cruises 50+mph

but there is no point gearing up the scoot if the engine is not revving clean under load, and if the cvt isnt working properly.

have you checked the obvious like binding brakes?
and are you using the stock exhaust?
the header is very restrictive on most 139qmb scooters - there could be a restrictive cone just inside the header - worth having a look!
no point making all that extra exhaust gas if it can't get out!

[Deleted]

Feb 27, 2012 18:10:57 GMT -5 vvtr said:

the header is very restrictive on most 139qmb scooters -

True but it works fine with a stock head and cam. I put a LV Titan exhaust on my big bore 82cc motor but there was 0mph gain because i use the sock valve head and stock 18mm carb.