Originally Posted by cannonball2
Im in Brunswick with a very nice house on the salt marshes/river. 10/15min from St Simons and Jekyll iIsland. Perfect area for my motorized bicycle amd M/C riding.
Is that a Preddy on your bike? If so why thoughts on a 4" roller? A 3" @ 4000rpm will get you 35 tops, means a leisurely cruise around 30 in the upper 3 thou range. I have different sizes for differet situations. If I were to say ride around town here I would use a roller around 2" for great stop and go. If I wanted to cruise up the coast I would use a roller closer to 3" to cover distances better. A direct drive trans(like mine) requires compromises in ratios, or patience with a lower more tractable ratio if you only have one. You showed my jackshaft set up is that what you are going to use, your bike looks direct drive.
I want a larger roller because that will give a larger contact area between the roller and tire. The roller in my case is on a shaft driven by a sheave. I can adjust the ratio by changing the sheave sizes.
My engine is a 79cc Predator,
That's not my drawing. It was in another thread on the subject in which you contributed.