BirdDog/bicycle-engines.com should have the grubee replacment parts you are looking for or will have them pretty soon if they are out. You also could check with Staton-Inc They sell clutches that work with the Honda/Clone motors as well but you will need to be able to use your old clutch bell with attached driver. You need to be sure that who ever you get the replacment from that its optomized for the Honda/Clone motors specs. These motors idle at higher rpms so the basic clutch for industrial motors won't work properly without modification to the springs.
i have one of the crappy gearboxes on my engine. I know about the broken gears and whatnot. I do not want to spend 100 dollars on another gearbox. my solution is to pull the gears, clean them up, heat them orange hot in a flame quench them, and then temper them to a blue. the reason the gears fail is becuase of the poor quality of steel they use and not enough treatment. I hope this works.
Why can't you get it from whoever supplied your kit Bikeuser? The clutch needs replacing about every 10,000 kms which is pretty good wear I reckon. The freewheel sprockets need replacing more often than that.
I get mine from my Grubee supplier in Sydney, Australia. MBB Imports for $25 for clutch and $10 for freewheel sprocket.
Any supplier who doesn't stock spares needs to be publicised on these pages so people know to avoid them.
Drilling holes in the clutch improves it's operational performance and its lifespan as per Cheetoh's idea -0 see attached picture.
Turning the clutch around also evens the wear on the pads.