With that big 7-speed you may want to consider a Jackshaft kit to make it a 7-speed shifter.
I really like the HS 142F with new 4G belt myself other than it is a full 1" wider than the old style due to the much better clutch housing and external offset bearing freewheel bearing mount.
Gears change everything for that little 49cc power plant.
It is pretty gutless off the line and limited to ~ 30 MPH with the stock 1 speed direct drive gears.
With just a simple 3-speed they jump off the line to ~ 25 MPH in 5 seconds and run 38 MPH with 26" wheels like this latest build.
SickBikeParts.com has a 4-stroke kit but it doesn't fully support the wider 4G well yet.
The BB shaft and crank combo is not wide enough but if you get the engine base high enough it's OK, you just have to drill new engine mount holes like this for example.
On that yellow build above I had to use the extra wide 'funky' cranks in the base kit.
Jim at SickBikes is working on a new base for this problem for their shift kit.
I have another 4-stroke shifter in the bay right now and another on deck so using my own design for now.
