Is there a clutch/sprocket combo available for 4 strokes?

Since the Chinese gearbox on my Honda clone engine broke on my first ride. I'm considering just putting a clutch on the shaft and going from there with an alternative drive train (to the chainring). I want to do away with the gearbox completely. Is there a clutch with sprocket that will fit these Hua Sheng 4 strokes, similar to the easily available mini bike and go kart clutches? The engine shaft isn't the standard size like 5/8" or 3/4". The gearbox had a clutch but no sprocket. The gears in the gearbox didn't even fit together.

HoughMade said:

The answer is yes, but you need a reduction of some sort to attain an approximate 18 or 19 to 1 at the rear wheel. Any centrifugal clutch that fits a 5/8" shafter will work, but they normally have 11 or 12 teeth meaning that the rear sprocket would approach 200 teeth without reduction.

Now, the reduction could be with a jackshaft. For instance, 10 tooth 40, then another 10 to about 48 would get you a little over 19 to 1...but think how much space that would take up. Now you see why they use gearboxes.

What gearbox did you have? Hoot or Grubee? Grubee is not perfect (none of them are), but it seems more reliable than the Hoot. Also, what went wrong with your gearbox?

Also Staton has an 18.75 to 1 gearbox and I'm sure that is quality piece.

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Yes, the Staton gearbox should be very reliable, but would not likely align up with the motor mount I presently have and it may not bolt to the engine I have.
The problem with my Hoot gearbox is first of all, a key stripped out immediately on the gear that turns the drive sprocket. The "keyway" was nothing but a tiny hole, so I saw no way to use a real key, so I brazed the gear back onto the shaft. No problem. Put it back together and the tolerances are so bad, the gears don't even touch each other enough to drive the sprocket under load. I've pretty much given up on the entire setup and plan to use an alternative mounting like I've seen several of lately. Just mount a centrifugal clutch on the engine and run the chain to a 72 tooth kart sprocket which I am going to mount on the chainring on the left side. The derailleur chain on the right side stays stock. Then I will have the bike's 7 gears to use. Good torque and good top end speed if I want it. I already posted a good example of a bike done this way. There's even a kit on ebay now that uses this type setup only it's an electric motor. Yes, it becomes a motorbike because I have to cut the pedals off since they would keep turning. But a freewheel crank could be used (available on the electric one I mentioned) so that the pedals could remain functional. The only concern I have is how well the derallieur chain will stay on under power. I plan to take it easy with it. I've seen this type of drive done in pics I have back to the 1940s, even one of them had a belt drive to the chainring instead of chain. I already have what I need, I just need a clutch/sprocket to mount on the Chinese engine. I'm using an Azusa live axle type sprocket mount and a 72 tooth sprocket that bolts right to it. The only work I have to do is weld a section of 1 inch live axle in the center of the chainring. It will take careful centering. Then I can just slide the sprocket/mount onto this axle and it will be adjustable back and forth. I know this is probably too radical for traditional people, but again, I've seen it done in several examples and the idea of having gears makes it interesting. The best example of one operating is a Schwinn chopper with this type drive on Youtube (below). It has a right side output engine, the opposite of mine, but the principle is the same. I mainly wanted to know if there is a clutch/sprocket that will fit the Chinese clone 4 stroke. The shaft appears smaller than your standard sizes like 5/8" or 3/4" like on minibikes and karts. With this setup, I'll definitely have all kinds of gear reduction, but it might take Einstein to figure out what it would be.
YouTube - Motorised chopper with 7 gear set up