79cc Predator

Fly1

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Down the line I would like to build a 79cc predator cruiser bike. been watching many you tube videos. Some thing that keeps popping us on these
builds is clutch chatter. Many changed to a torch converter. I don,t want to run a TC for many reasons. But going back to the cylindrical clutch chatter
problem one guy attributive to the gear ratio. Even though they were running a jack shaft maybe the rear sprocket was to small. Has anyone here looked
into this?
Fly
 
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5-7HEAVEN

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It is a scientific fact that high gear ratios will destroy clutches.
This is also true on cars, trucks and heavy machinery.
When selecting gear ratios, it’s better to start low.

FYI, low gears are higher numerically.

Smaller engines need lower ratios.

My 47cc Tanaka engine needs a super low 1st gear of 40:1 and 8th gear of 12:1.

However, my big 212cc engine will have 1st gear of 9.24:1 and 6th gear of 4.35:1.

Your bike might be slower in speed, if you experiment with low gearing. but at least nothing will break.
 

Fly1

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Great reply! Do any here know the final gear ratio for a 79cc predator with jack shaft? I will be running 26 inch wheels
 

Chainlube

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Great reply! Do any here know the final gear ratio for a 79cc predator with jack shaft? I will be running 26 inch wheels
That all depends on what gears you select. If your running a centrifugal clutch, say 10 or 12 tooth back to an 18t on the jackshaft with a 14t back to a 48, 54 or 60 on the wheel, so many combinations.
 

5-7HEAVEN

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Great reply! Do any here know the final gear ratio for a 79cc predator with jack shaft? I will be running 26 inch wheels

Search the two forums for the gear ratio that work for 79cc engines.

Then we can help you decide which sprockets work well, to get that ratio.
 

CrazyDan

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We need figure out torque needed to move x amount of weight on different grades and the usable reductions. We might be able to make a graph that can figure out what can be expected (approximately) with each engine and the best reductions to use based on torque, rpm, weight and grade. This can all be done with each individual engine, but you need to figure out your power output then use multiple calculators to figure out the best ratios for it. Anyone here skilled enough to make a doohickey that can give a power output needed so people know what engine and ratios are needed to achieve their wanted use? Something that needs total weight, grades, wheel sizes then wanted speeds. I'm pretty sure it would be a bit complicated because it's adding multiple calculations together, like mixing a gear ratio calc, a power to potential speed including drag and grade calc and God knows what else. I don't have much issues doing these calculations myself, but many do... and I wish I could write a program to cover it all and idiotproof engine and sprocket selection for anyone that have a hard time knowing how to transfer numbers from one calculation to another.
 

Will'smotobikes19

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"79cc predator cruiser bike. been watching many you tube videos. Some thing that keeps popping us on these
builds is clutch chatter. Many changed to a torch converter. I don,t want to run a TC for many reasons."

The grubee transmission seems solid and it has a needle bearing belt driven design meaning less noise probably better than the bushing clutch. Just discovered the other thread. It isn't a true torque converter but uses a belt. IF the ticket is homemade needle bearing clutch should still work.
 
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