Bubble balancers are supposed to be pretty beat for balancing a motorcycle tire. I used to do mine and spin balance them and it was accurate. I had the harbor freight setup and it came with 2 metal rod for placing inthe center of the wheel when removing tires.....I would take the rod that would fit in the wheel and then place the wheel and rod on 2 jack stands and spin it and wait for the heavy spot to stop at the bottom. Do this 2-3 times and make a mark each time, it should be the same spot over and over. Another helper...spin balance the rim to find the heavy spot with no tire on it and mark it on the inside ( only needs to be done once, then it is marked forever ), that way you can figure out where to place the dot on the tire, which I believe is the heavy spot. Go to a NAPA or other parts store and pick up the tape on weights, they are cheap and easy to use and I never had one fall off the wheel.