I recently acquired a Schwinn S350 and immediately upgraded it to 36V.
Here's some things that I have the parts available for but wonder if they are worth trying.
1) Replace the S350's motor with a 500W motor from a broken Scwhinn Tsunami.
2) Replace the S350's speed controller with the controller from a broken Stealth.
3) Run the S350 at 48V
4) Replace the S350's front end with the front end of the Tsunami. The S350 has no shocks and no front brake. The Tsunami does have shocks and front brakes.
Would appreciate your comments.
I have changed out solid front ends on scooters to ones with suspension, and it makes a noticeable improvement in ride quality. Getting a front brake is an extra bonus. You will need a headset wrench to take things apart (either 32 , 34, or 36mm). You have to make sure both scooters have the same type of steerer in size and threads-also some scooters had a taller head tube. Be careful about the headset bearings when you are pulling things apart. On some scooters, they are loose in there, and will fall all over the place. You can always order a new set of bearings.
Changing the controller by itself won't do much. The 500 watt motor should give a noticeable improvement. Running either motor at 48 volts should be done by changing the controller to a 48V controller, which means some playing around with wiring. that will make a big difference in speed, but then you need to fit the extra battery. if you run the motor hard at 48 volts, it will get hotter and wear out faster than at 36.