The Styrofoam battery/ignition coil holder in my bike is kaput.( 31505-147-020 HOLDER, BATTERY ) the ones I've seen for sale used are in very poor shape. I was thinking of using a plastic trash bag and back-filling the open areas with expanding insulating foam. Is this a good idea or have you found a better way? Thanks.
I got a old Tabaggon keeping mine in a spot on my scooter. I imagine you could use what you say, but with the expanding foam I would put something like Card Board around the Battery so It does not stick to the Battery.
I wrapped the battery in a plastic bag/tape and smeared silicone grease over the plastic. I set the battery in the "divot" at the rear of the seat stamping and filled around the battery with expanding insulating foam.* I let it set up 24 hours. The battery and plastic/tape slipped right out of the cured foam. The battery is now held well and is padded. I will do the ignition coil next. It is very easy to do. *Any excess foam can be trimmed with a box knife or hot wire cutter.
You did good. Spending a lot of money on some thing old is nuts unless you have a cherry and expect a good return on completing a restoration. In the case of cars people restore and pay to restore and then find they could have bought one just as nice for a lot less.