Hemmek post=846311
I must clarify one thing thou, I didn't intend to replace the battery
Just helping out with the voltage drop during the starting event.
I realize I didn't actually answer your question directly. I was really just curious myself to work out how a capacitor compared to a battery in terms of energy storage.
You're not alone in thinking that super caps can be used to supplement lead-acid batteries. This is one that I found that is advertised for exactly that purpose.
media.digikey.com/pdf/Data%20Sheets/Skel...elStart%2012V_Br.pdf
Of course this one is $1217, so maybe not really practical at this point. But the idea is sound enough.
However, a normal AGM battery in good shape should start your bike without any help. The other day I started a '74 Z1 with ~1250cc and ~12:1 compression with a 1/2 size battery because that's all I happen to have handy. I did maybe 6 starts before it noticed it start to slow down.
If you're having trouble with slow starting, you either need a new battery, to check your charging system, or do some work on your harness.