I don't have the Honda but do have the HS 142 - 49 cc motor with the 4 G T3 clutch and drive. On my initial assembly the out put sprocket would only freewheel in the forward direction. I did call the distributor and got information on things to look for. I completely dismantled it and found nothing wrong. I very carefully put it all back together and it worked. I do not believe in the old take it apart and put it back together theory but this time it worked.
After running this for awhile I think I would be happier if I had purchased a slipper type clutch instead of the centrifugal clutch. Oh well there is always another build
I've had mine for nearly 3 years, and while I had to deal with some teething problems, I consider it to be most versatile system out there.
The shifter 4G is extremely engaging, abrupt in it's movements, and quirky with it's freewheeling. But I
love mine. Cruise 5-35 quiet or loud.
The Huasheng 49cc makes ~2HP and 2lb/ft with good exhaust and intake, and it will slow down with any incline or headwind without pedaling.
Set up properly, it can be a snarly lil thing that really does it's best work 5-7K RPM, it's up to the builder to get it straight.
The centrifugal can work very well, but you may need to add washers, like I said. The washers effectively increase spring pressure.
You'll ideally want ~60lbs/in. You might want to buy another clutch so you can play with the old one.
Also, I highly recommend using KMC HL710 on the 11/17 part or, the jackshaft input. This chain has great adjustability and longevity.
You can use it on j/s output too, tracks nice.
I currently use HL710 on input, #35 (9/76) on j/s output, and 415H from crank to hub. Used many other chains, but these last!
My SBP input uses an 18T Staton gear, HL710 gives perfect length easily regardless.
That pic I was using a 410H on 44/15 with (75/100/133%) Sturmey X-RD3. The 410H got sloppy quickly, spot the sprung idler!
Shifter 4Gs require a certain finesse to build and ride, but you get to know it well and it will reward you with a visceral experience at any speed.