choosing a bike to use?

[Sidewinder Jerry]

I put the chain on the granny gear and throw the derailleur away.

With a single speed your ratio options are limited if you need to pedal assist on a very steep hill. If your engine can't reach max torque rpm going up a steep hill you'll have to pedal assist to reach it in order to avoid engine strain. With a single speed your choices are increased cadence and/or pedal meshing. With a multi speed you can stay seated while using a ratio that allows you comfortably maintain a cadence that let's you reach max torque rpm. You'll know if you're using the right ratio for pedal assist to avoid engine strain if you use a tachometer.

If you're a flat lander then a single speed is fine.

 

[Freddy Snottgrass]

Can I use a ten speed for my build. Or do I have to have a single speed. I know the motor won't be shifting.

You can use a geared bicycle. I think using a geared bicycle is better for a new builder since you won't have to mess with chain tensioning as much. Also, I did leave my derailleur on with a single speed, just had to know which selection kept it on the sprocket.

Essentially, you have to tension adjust two chains. Having one adjust automatically is a big benefit. You can use a geared bicycle, pedal easy in low gear when starting and when you are a mile away and it quits running. You can use a single-speed with a derailleur and work a little more to pedal and find the sweet spot on the selector. Or you can use a single-speed bicycle, pedal hard, and fight to tension both the engine chain and the pedal chain.

 

[Sidewinder Jerry]

You can use a geared bicycle. I think using a geared bicycle is better for a new builder since you won't have to mess with chain tensioning as much. Also, I did leave my derailleur on with a single speed, just had to know which selection kept it on the sprocket.

Essentially, you have to tension adjust two chains. Having one adjust automatically is a big benefit. You can use a geared bicycle, pedal easy in low gear when starting and when you are a mile away and it quits running. You can use a single-speed with a derailleur and work a little more to pedal and find the sweet spot on the selector. Or you can use a single-speed bicycle, pedal hard, and fight to tension both the engine chain and the pedal chain.

when you are a mile away and it quits running. You can use a single-speed with a derailleur and work a little more to pedal and find the sweet spot on the selector.

Not exactly sure what you're saying here. Are you saying if your engine quits you'll have a multi speed (ratios) to get home on vs getting home with only a single ratio? If this is what you're saying then that would be correct.

When it comes to pedal only power if you can't comfortably maintain a cadence (crank rpm) of 70-90 it means you're in the wrong gear. With pedal only power all gears are comfortable to use if you're in the correct gear

With a single speed if you can't comfortably maintain a cadence of 70-90; you then have to stand and mesh the pedals. Even then you may find it too difficult to climb some hills using only pedal power.