Topic: 78 750K - Charging problem

[ZanVooden]

So finally got the 78 750K out the other day to get some miles on it after its recent rebuild. Unfortunately I had some charging issues I was hoping some body here could help me with.

I had run the bike once a month over the summer and when I was warming it up the other day it started fine but then died trying to warm up. So I got the charger out and charged the battery, no big deal there. Got it running again and got out on the road. Everything was going fine on some country roads till I got in to a small town and stopped at a stop sign and took off and the bike died. Hit the starter button and it turned a couple times very slowly and stopped dead. I had no choice but to ask for help from a passing 62 chevy. He helped jump start the bike. I got up to the next stop sign and it died again and same dead battery. The 62 chevy guy helped me out again and I nursed the bike home on blacktop roads, not stopping at any stop signs.

Now when I got the bike it didnt run so I dont know if this was a prior issue with the bike or sometime I created in my rebuild. I know jump starting a motorcycle off a car battery can hurt the electronics on the bike. Might my rectifier be shot? How do I check this?

Does anybody have any idea where I should start in fixing this problem? 

Dave

[TwoTired]

Start by charging the battery and being certain it is good.  Having it tested just might save further troubleshooting.  After you have a fully charged battery that has rested for 2 hours, it should read at least 12.6v or 12.8v.
Install in bike and kick start.  Measure battery voltage at idle, 2000, 3000, 4000, 5000 RPM.  Hold 4-5000 for a few seconds to see if voltage continues to rise (indicating the battery is recharging).

Report findings for the next steps.

[Inigo Montoya]

Have to second the battery. I had an older style lead acid at one time and the cells went dry. As you can imagine, it did not hold much charge. So if you have the style where you need to add water, check that. If you have to add water, I would see about getting the battery tested after that. It may be damaged internally. If you do have to replace it, get at least a sealed Maintenance free or my favorite, an AGM battery.