New to the MotoBicycle world.


New Member
Mar 5, 2019
Hey folks. I'd say i'm a long time lurker of the forums, but i've only had my bike for about 2 months now. It was given to me by my father who couldnt ever get it to stay running for more than a minute. If i remember correctly there was something wrong with the carb causing it to kill momentarily after starting. Either way, i've got her running fairly smoothly. I've had a few hiccups the first few days. The carb float kept getting stuck causing a leak, so i bent the metal prongs down a bit. I do have a few questions though, maybe you guys know a specific thread for me to check out.
1) the plastic piece on the kill switch that the throttle tube screws into cracked. and I think the plastic keeper stripped out, so the piece that the throttle cable wraps around kinda spins around. I see I can buy replacements for the piece, but is there anything sturdier I can buy?

2) someone gave me the HP carb from bikeberry. At low/mid throttle it runs/idles great, but at full throttle it bogs down a bit and the RPM goes flat. it getting too much fuel? Not enough? Should i rejet it to a smaller size?

3) is there a definitive goto guide that has a start to finish product build? I tore the top end apart and started sanding/polishing the ports/head a bit, but i'm looking to actually open/widen the port a bit without adjusting the timing. I did chamfer the intake/exhaust port slightly, and put a small window on the intake side of the piston, but at TDC part of the piston it still covering the intake. I'll probably take it back down and open up that piston skirt a bit more.

I'm fairly mechanically inclined. I've worked at mechanic shops in my early days, and I'm a structural/architectural steel fabricator/welder currently. So I'm fairly confident I can handle modifying things without destroying the motor.

Thanks in advance, sorry for the lengthy intro post

/edit Forgot to mention its a 66/80cc China motor



Well-Known Member
May 1, 2011
Welcome to the forum, it does sound like you have a jet that is too large, the best way to check is by spark plug color. The porcelain insulator should be brown in color, search “plug chop” and you’ll find a lot of info. Notching the piston does help to wake up the engine, too much notch will harm low end, I mark along the intake port with a pencil then remove the piston and trim out the area.