Got a new toy recently on craigslist. A Chinese clone of a Honda SS50 that hadn't been run for over a year and had a broken sprocket hub on the rear wheel, but was all still intact otherwise.
I got it home, got it to start roughly just on the old gas left in it, and called it a night. The next day I went to the local motorcycle junkyard CycoCycle, and managed to scrounge up a close match to my broken hub, only it was cast with about twice the aluminum and looked much sturdier. After getting it fitted and installed I managed a shaky and sputtery ride around the yard with the motor jumping around under my feet.
One cleaned carb, properly replaced engine anchor bolt, fresh oil, a newly fabricated chain tensioner, fresh gas, a new fuse, cleaned fuse holder, and a new battery, and I had it running..... WORSE. Actually it was running much better, but I'd managed to lose the carb settings while cleaning it, and couldn't manage to get it idling properly. It would get up to 40MPH without trouble, but that's all it had. Not bad for about $150 invested in it including gas and oil, but I was wanting more and not wanting to mess with tuning a carburetor if I could help it.
I went online to Planetminis.com and found a nice looking 110cc motor that looked like just the trick and got it for a decent price with the carb and all pulled right off a running bike. A few days later I dropped the original motor and heaved the heftier 110 in place. Then all I lacked was finishing.
Finishing turned out to be a little more involved than I originally planned for. I had to rewire the stator plug from the original (my cheapo 12v impact wrench was fantastic for this), pulling the flywheel to make sure I matched the correct wires to the original plug. I then installed a fuel cutoff valve since the original was MIA, swapped the original motor's drive sprocket on, installed the throttle cable, and was then struck with some problems:
* No spark
* Clutch cable won't reach on new motor
* Mounting bracket hole for muffler doesn't line up
* Foot pegs won't fit between bigger motor and exhaust pipe
I wound up having to figure out the pinout for the gear indicator light, which also acted as a kill switch if the bike wasn't in Neutral when kicked over. After that was sorted I just wired the N pin to ground and wrote "ON" over the neutral light. Now I won't forget the key in there! :P
The clutch cable wasn't too hard to fix. It would have had the same amount of travel even with the right cable, it just needed to be a couple inches longer. After sizing up the situation I ground a notch in the side of a bolt, welded a nail to it, and slipped it in place between clutch arm and clutch cable. Works perfectly!
The muffler mount just needed a notch cut in it so it could slide far enough forward to meet up with the slightly longer motor and still meet up with the bracket's bolt hole.
The foot peg was a serious pain. After trying to shave down some meat to make it fit for about an hour so I wouldn't lose the proper positioning of the peg I gave up, lopped the original right peg off before it bowed up to hit the motor, and welded a new bit of steel rod sticking out while it was all bolted in place so I knew it'd have to fit cursing and burning myself with the welder the whole way. I then eyeballed the foot peg and welded it in place, putting solid beads in with it all in my vice so I wouldn't have to curse and burn myself as much. After that it slides in place great through.
Now on a test run through the neighborhood I can get it up to 50 and I'm guessing it'll make it between 55 and 58 on the open road. Once I toss an air filter on there I'm not sure if I'll sell it or keep it around and put new tires on it. It's very fun to drive and is nimble enough to almost treat like a dirt bike.