ThatsDax:
bicycle engine kit, bike engine, bicycle engine, bicycle motor is one of the best for customer service I've ever heard of! I'd get my motor kit from him if I were you

Spooky Tooth:
Spooky Tooth Cycles and BikeBerry:
Wholesale Beach Cruisers, Chopper, Mountain, Road, Tandem, BMX FreeStle and Bicycle Engine Kits - BikeBerry.com are favorites of mine, they've treated me
very well.
Yeah - and a lil "heads up" that I wish I had known lol
The motor will most likely run like **** for the first 100-200 miles, other than gently torquing all fasteners and making sure you don't have any air leaks - don't worry about it, the rings haven't seated yet - it'll be a completely different engine once it's broken in.
Also - the "instructions" (such as they are lol) recommend 16:1 - 20:1 mix for your break in. This is excessive and is prolly because of the cheap 2stroke oil/motor oils they use in China - I'd recommend anywhere from 24:1 - 32:1 (depending on courage/engine response) with a quality (but nonsynthetic) 2stroke oil, then once it's broken in (may take up to 300mi) you can switch to a synthetic if ya want
I suppose the biggest thing is get Jim's sprocket adapter:
SPROCKET ADAPTER - that is by far the biggest problem w/these bikes. The second biggest is the tensoner, advice can be found here;
http://motorbicycling.com/f11/chain-tensioner-suggestions-11815.html