50cc Bike

View attachment 75438 Recently finished putting this motor bike together. It's probably the 5th I have ever built, and now that I have access to better tools at UCLA I tried to increase reliability and overall strength / integrity in ways I haven't been able to in the past. I got the motor kit on eBay for $98 and the bike for $20 on Craigslist.

first thing I did was weld a front motor mount and properly shim the rear, as the motor mounts on the engine where slightly too big for the bikes tubing.

The rest of the build was pretty straight forward. mounted the tank on the rear rack. I also cut up the stock exhaust and welded it longer using electrical conduit. This has a good effect on power, but I want to remake one with smoother curves, as I wasn't using the tubing bender correctly when I tried it the first time.

only thing to be done at the minute is fix the head gasket leak, port everything, and trim the piston so it doesn't block the intake at all. it already runs pretty good, but with that stuff done it should scream. I would say it tops out at about 28 mph right now, mostly limited by the 44t sprocket, but its got a lot of low / mid range power. I also want to mount the CDI beneath the engine, but I need to get a longer plug wire before I can do that.

Ive been having fun building this bike "super stock" i.e. only with modified stock parts. I've built some bikes with lots of modified moped parts etc. which is a good time but this is fun in its own way


I'll keep updating this thread as the build continues

 

[motorbiek]

took some updated pictures today. i welded a rack around the rear gas tank. seems to work good! carried a fat cinderblock on it today and it was fine

 

[Frankenstein]

Out of question did you leave the rack on the bike when you welded it or took it off. I hear that you can't or shouldn't weld to anything on the bike with the magneto and cdi attached or it will burn them out...

I can't make heads or tails of that idea so if you left it on and you aren't having problems let me know please. Thanks.

 

[motorbiek]

Out of question did you leave the rack on the bike when you welded it or took it off. I hear that you can't or shouldn't weld to anything on the bike with the magneto and cdi attached or it will burn them out...

I can't make heads or tails of that idea so if you left it on and you aren't having problems let me know please. Thanks.

I left it all attached, and didnt have any problems. I also grounded the welder pretty close to where I was welding. I can imagine that if the ground was, for example, on the handlebars, more current would potentially pass through the electronics and kill them. maybe?

 

[Frankenstein]

I left it all attached, and didnt have any problems. I also grounded the welder pretty close to where I was welding. I can imagine that if the ground was, for example, on the handlebars, more current would potentially pass through the electronics and kill them. maybe?

I figured that if the ground was close it shouldn't be a problem, and I understand electricity wants to take the shortest path, I couldn't think how or why any current, ac or not, would want to go through the electrical system if you aren't actually hooking a ground or arc tip up against it.
Thanks.