79cc Predator and CVTs

MEASURE TWICE

Well-Known Member
Jul 13, 2010
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I just thought of another idea, and it only would require a larger diameter 3/4 shaft pulley that uses a keyway. I could use my top jackshaft to mount the centrifugal clutch that is 5/8 shaft as is the jack shaft. All I would do is be sure the pulley I buy for the engine is the same as the existing belt clutch pulley. That way the engagement of the clutch at 2000 to 2200 rpm stays the same and 1750 idle I am stopped with the engine still running.

The gear ratio I'll still have adjustment since I got a larger sheave on the rear wheel from when I first designed my bike with two jackshafts. Now since I have the top jackshaft connected to the bottom jack shaft with the same gears, I could swap back in the 1 to 3 ratio set up gears there and use the shorter chain between the top and bottom jackshaft and have the same overall ratio and torque/speed.

I'll look at it soon and see what could be. The torque converter maybe for another time as it costs a few bills anyway.

MT
 
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MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,340
316
83
CA
I thought again and know it can't use the clutch on the jackshaft if I am to also need to have gear reduction as the clutch it too big a diameter. Small diameter driving a larger diameter is reduction and there is not enough room between jack shafts.

Going to push start maybe or lift the back wheel no clutch idea came to mind. Then I may use a chain and gears to transfer from 3/4 engine crankshaft to 5/8 top jackshaft.
With 11 tooth to 28 tooth which reduce 2.54 there. Top to bottom jackshafts I'll use 9 tooth to 13 tooth which reduce 1.44 there. Then the bottom jack to rear wheel sheave already set as adjustable diameter pulley at about 2.5 inch to 16 inch which reduce 6.4 there. Total reduction 2.54 * 1.44 * 6.4 = 23.4

I've in the past had a 24 inch wheel motor bike using about 2hp with much lesser reduction maybe 2 inches pulley on engine direct to 14 inches giving a 7 reduction.

I was able to start that engine by push starting and when warmed up only 2 feet forward motion and it was put put slow to get to speed. The roughly 3 times greater reduction would mean I would be trying to spin the engine by turning the rear wheel with 3 times the force across less distance about 1/3. 3.5 hp will give more resistance starting the compression stroke, but I'm thinking this could be a hill climber an no clutch is simple, to see?