Crankcase to transmission conversion.

[Paradox1559]

I just got my kubota zb600 running, so now I need to figure out a gearbox. On my budget, my best option is an old dirt bike/motorcycle crank case. So, I have a 13hp@3200rpm engine, and an old honda 2 stroke 50cc engine. Would that be too small for my motor? Furthurmore if it is ok, would it be ok to rotate it vertically so the oil rests at the bottom(back)? That way I can use more space.

[sbrumby]

Everything is built to a spec, 50cc sounds on the weedy side, bear in mind your engine will give at least 26 ft/lbs, will the 50 cc cope with that? On the question of is it OK to tip up the gearbox, no problem mine has been running for 10 years. Just another tip don't link the two together with a chain unless it is immersed in oil as it will only last a couple of hundred miles, V belts work better and cut down on vibration.

[gilburton]

I wouldn't think the clutch on a 50 would be strong enough let alone bearings/gears. Personally I would be looking at 250+
I don't know if there have been any articles on using cut off gearboxes but I would like to know myself. I know cb250 boxes/crankcases have been used but not how they have been accessed to get drive.

[Paradox1559]

I've seen a couple people weld a sprocket to the clutch cage. I've also seen others that run off the stator, because they didn't cut the crank case. They just removed the cylinder and piston and capped the holes.

[sbrumby]

On a lot of 2 strokes the crankshaft drives the clutch via a gear, so the way I did mine was to replace the crankshaft with a straight shaft with the original gear on the end. all that is required is to cap off where the cylinders were the gasket is the perfect template. Remember to seal this up complete with oil, the bearings love this as they were only fed with a mixture before.