On my bathroom scale, both the stock and the Malossi white that came with the multivar were 30kg to fully compress.
It was said that it were a 50cc 4-stroke and not a race bike, which is right, but it doesn't mean that it cant become a race bike.
If a 50cc race bike were wanted, you should change the clutch springs so it gets traction as close to the max torque as possible. Also, you would want to tune the exhaust and intake (info about that
here) and you would like to get 4 valves instead of 2 and a CDI without restrictions.
But i sense that you just want to get it to ride good, and then these changes wouldn't be very economical or practical.
Anyway, back to the vario tuning:
With 6,2g rollers and the stock spring, the accelleration happened at 7200 rpm for me, but with 7g dr. pulley sliders, the rpm were at 7450 during accelleration, which is a little high for my taste, as it is over the max torque according to the manual, and it lead to slower accelleration.
I will try 8g Dr. Pulley some time soon, to see if i can get the rpm closer to 7000 during accelleration.
The torque springs have 2 purposes:
1) To keep the belt tightened during accelleration.
2) To force the gearing down, when the throttle is closed and there are no longer enough torque to keep the gearing high.
For the tuning part of the torque spring, we mainly focus on the second purpose, as rpm can be kept high during decelleration, if the gearing is forced down very fast, but a stiffer torque spring also have disadvantages, when our engine are so weak from stock.
To accellerate, the engine will have to generate torque higher than what the air- and rolling resistance, the weight of the bike and driver and the torque spring does against the engine, and as you could imagine, a stiffer torque spring will remove more torque from the engine and therefore reduce the overall output of the torque on the rear wheel. Normally, we say that the vario transmission have a 10% torque loss, but with a stiffer spring, this might be alot higher and you will get slower accelleration and less top speed if you haven't increased the torque output at the crankshaft aswell. :p
It also hurts the fuel economy, as you will need to turn the throttle more to get the same amount of torque at the rear wheel and because it keeps the rpm high during decelleration.
The high rpm are what is wanted at race engines, as they almost never hit top speed because of the many turns on a closed track.
Where the effectband lies also depends on the exhaust and intake system, so with the different manifold and exhaust, the effectband might have been shifted a little for me, as it seems that it has faster accelleration at 7450 rpm with the carb and 16mm intake manifold than it has with the 24mm throttle body and manifold that came with the injection, but this might be partially caused by a wrong mixture with the injection at the moment.
