Motorized bike project

[Longshot270]

One of my many irons in the fire, this one being the most time consuming (by choice).

A few months ago a neighbor gave me the frame to a Specialized Rockhopper. I already have a hard tail trail bike so it was laying around unused. About a month ago I stumbled onto a motorized bicycle kit that was on sale for $179, I figured it would be cheaper to go on small errands and to nearby fishing holes.

After about 4 hours after picking the engine up from the Post Office I had the bike "running"



After working out some big bugs like sub-standard chain and engine sprockets. Then working out some smaller electrical issues and adding a rack and other cosmetics, I had this.



Got past the 50 mile break in and started trusting it for better trips. With the finiky carb working well I could cruise easily around 20 and had a top speed ranging from 27 to 33 mph.



After riding it yesterday I realized that I'd like some more speed. The first issue, which I knew was going to be a problem early on, was the mountain bike frame was just too tall. I had originally toyed with the idea of putting it on my blue commuting bike but having no suspension was not going to a fun ride. I needed to lower CG and wind profile some so I decided to do an engine swap. I fabricated a new front assembly with parts from a scrap bike to give me front suspension. Next, is to work on the exhaust. It currently doesn't have one because the pedals did not clear the muffler...but a hack saw fixed that real quick. This weekend I'll find someone to weld it back together in a way that will work. I've also got a smaller rear sprocket in the mail that should arrive in a day or two. Switching from a 44 tooth sprocket to a 36 tooth sprocket should bring my cruising RPMs down quite a bit and make have my power band end around 30-32 instead of the current 24-26 mph range. I'm not expecting the claim of 8-10 mph increase because that comes out to be a calculated estimate, not a tested one, but I do expect my top speed to be load based rather than RPM based.