Originally Posted by romerider153
Kc so I'm confused a 49cc with a three speed in your opinion won't do 40...
(what) would you suggest for a 5'7" 125 pound girl to be able to hit 40 if need be.
Oh heck ya, with her size she could run 40 on an aluminum frame 49cc shifter easy.
I pretty much base all my speed estimates on a 6' 180+# man on a steel bike.
This Genisis 7-speed for example would be low and light enough for her to handle and do 40 easy.
Heck, I am 6'1 and 165# and did ~45 with a 53cc and better exhaust and spark plug.
For her size dual V brakes could stop her well too.
I am trying to remember spoke count but pretty sure it is over 36 so a direct drive rag joint sprocket won't fit it.
Speaking of which, it is really best to decide if you want to go shifter or direct drive first as it's twice as time consuming and expensive to switch from DD to shifter on a 4-stroke as besides the base, even the bottom bracket needs changed.
Also note that a 7+ speed has about the same gear ratio between high and low as a 3-8 speed internal, just more steps in-between, a thinner drive chain, and it's only in-line in 3-4th.
Dandy for human power pedaling but a waste for engine power.
Hope that helps.