Re: Motor bogging at start up low speed
I live 20 miles west of Boston, and actually just finished installing a 49cc kit for a guy that saw me running around on my Schwinn Point Beach. He supplied the bike, a Rat Fink chopper (check them out online). This second build took some time as I had to build custom mounts to accomodate for the wide back tire. The engine is mounted about 1/2" to the left of center frame. I had to figure out the mounting of the sprocket to allow use of the coaster brake. I just bought a hole saw big enough for the brake housing flange, then made a holder for the sprocket that had a pilot hole for the hole saw bit. worked great.
I'll try to upload some pictures of both bikes.
To answer your question, it could work either way. They could supply the bike (like my guy did) or you could buy bikes. My suggestion is that you have the customer pony up the money for the bike and kit. Then they pay you the balance for installation when the bike is complete. Just be up front about what the total cost is. Nothing says you have to break down the costs. Just give them a total.
I thinking of doing as a side line. Once you get the build details down, you can put these things together pretty fast. Custom bikes should cost extra as there could be many issues to overcome. Good luck.