Well here's my two cents: I like 4 strokes better because they are quieter and
use straight gas; no need to add oil to the fuel. The biggest issue I see with
4 strokes is not the engine but the transmission. Belt drives are preferred
over chain, but the China kits come with brass trans bushings that require
greasing. That's why I converted my belt drive to an oilite bushing which
does not require grease. The best advice for a reliable 4 stroke would be
to use the Grubee belt trans that uses real bearings, or the EZ Q-matic
belt trans (expensive but tough), or convert the China belt drive
to an oilite bushing. I found a great combination for quiet, smooth,
easy pulling from a dead stop is the 53 cc, 4 stroke, using a 41 rear
sprocket, and converting the belt drive to 4:1. The thing is so good,
I regret not putting the whole kit on a better bicycle, that has
disk brakes and front suspension.
