I got a 72 350 with a bit of a charging problem. Put a brand new battery in, and she'll pop off, but then die in about 5 minutes, and then she won't start again. Have to kick start her from there, but no electric start. She won't hold a charge at all. Don't want to run at all. Thoughts??? She was working fine, then this just started one day.

 

The biggest cause of charging problems on these machines is the rectifier. It is usually the orange finned thing.

But if the battery is dying real quick, you need to check further. What you need to do is check the current flow in and out of the battery. For this, it helps if your multitester can read to 10A, both + and - (a digital multitester can, analogs usually can't). Connect the meter between the battery + and the red lead usually screwed into it. Check the current flow with ignition on, to see the static current draw. it shouldn't be higher than about 5A max. Then check with the engine running, it should show a slight positive current at around 1500rpm, and about 2A around 3000rpm (all figures approximate).

If you have a second multitester, connect it across the battery terminals too, so as to see the voltage. It shouldn't drop below 11v, and not over 14v.

This way, you can determine whether you have a short or a charging problem.

If you have a short...have fun finding it and if not I'll bet dollars to donuts that it's the rectifier.

 

Was a 1972 Honda 350. I had that happen all the time. I inevitably found one of the conductors somewhere shorted against the frame. No real rhyme or reason to it. Just somewhere there would be a short. Always found it on visual inspections by gently feeling along the wires and checking and scrutinizing any strap and contact points. those scooters are generally bullet proof. They're like an old Ford, they'll always run when nothing else will. I ran one of those little buggers from one end of the southern states to the other and then from one side of them to the other. FUN!!