battery voltage dropped then jumps up after sitting

[miahlaw]

So I noticed my bike was not firing on the right cylinder. Had it running... so I took off the carbs, cleaned and all that. Battery showed 11.7 on the voltage meter.
For some reason my battery dropped from 11.7 roughly to 5 volts, not running, just dropped and would not start. It seemed when I checked the right spark plug for spark it just juiced the battery.
I kicked and kicked and it would try, but no dice. after sitting for 3 hours, the batteries voltage is back up to almost 10 volts? Started right up but the right cylinder isn't firing. While running the battery shows 5 volts again...this stuff just confuses me...
I know the guy I bought it from re wired it and simplified it, I think the reg/rec might be bad and I have a different reg to put on it but havent had any issiues til today.
It seems if both cylinders are firing it wont run, like it sucks all the juice if the right cylinder tries to fire.
Anybody else have this problem.
(Right cylinder as if your sitting on it.)

 

[miahlaw]

also any advice on new universal coils? im thinking thats my issue...from what ive seen new coils are going to run me 160+...
that or keep buying used ones that may have the same problem...

 

[buschkj24]

Start out with a new battery... Sounds like a cell or two are dead. If that doesn't fix the problem then start looking at the PO's rewire job... Probably not the best idea for him to rewire it but whatever trips his trigger.

 

[willem]

if a battery drops below 9v at any point in time, it's dead

I've had a brand new one that did that. Batteries are strange creatures. Sometimes they last a decade without any trouble, sometimes they die within a week of manufacturing. Check your wiring and charging system once you get it running again, too. If your regulator is broken, your bike may have fried the battery.

On ebay you should be able to find some decent and cheap coils. There have been a few threads on this here, so do a search