[serialk11r]

Enki have you considered pairing the motorcycle battery with a small cap bank? As demonstrated by the video in the original post, you can start the car with a surprisingly small cap bank thanks to the high power density. Your motorcycle battery sounds like it's still good to go.

My own plan is to go for a Deka ETX12 battery next time around (so a little less than half the capacity of stock), lead acid since I feel like there's no reason to put that big of an investment in at this point, and 6 400F ish capacitors. If it can start a V8 it can surely start my wimpy 1.8L 4 banger. The smaller capacitors will also bleed less current which will help.