Stop-A-Flat (solid inner tube).

[Chopperoad]

I got the right size in there and the tire is slipping on the rim.
I didn't have that problem on my 10 speed. So bewear is you go this route. It also says Not for motorized bike's.

 

[Chopperoad]

My top speed now is about 15mph cause the tire wobbles. Other reviews said it worked on motor bike, well not this one ~