I recently took the sporty to a hardtail and a lot of the wiring was redone. Now, I ran off the original battery that was previously in it and everything was fine initially. After a while it had trouble starting the bike so I replaced it thinking I'd had the battery a while and it was time. Now I've had a battery about a month and the same issue is occurring.

At this point, the bike seems to jump start fine, but if I jump it and immediately remove the cables, the bike runs odd and will stall unless I'm revving it. With the bike off, I'm getting 12.8V, but as soon as it turns over And I pull the cables, I get between 4V and 4.3V. What's going on?!

 

Doesn't sound like you keep the battery on a tender to keep it charged. Sounds like something is slowly draining your battery and it is never getting fully charged back up. Your going to have to check your grounds and wires to make sure you have good connections. Make sure you don't have a wire that is pinched or cut. When you did the hardtail was it a bare frame. Cause you have to be careful welding with all the current going through electronics and wiring.

 

What's the condition of your charging system?

 

It may be overcharging or undercharging the battery, first check all of the connections as suggested above. Go buy a battery tender and fully charge the battery, then start the bike and using a voltmeter on the battery terminals bring the idle up to 2000RPM and hold it there, you should see 14-15 volts if your charging system is working properly.

 

If while doing the mod you painted or have any fresh paint in the area where ground connections are, clean it up by removing paint.

 

Although I wasn't keeping it on a tender, I do have one and I did charge up with it at one point. However, once fully charged, it didn't turn the bike over. It was a click and then nothing. After that I couldn't even get a click off the battery.

Now once I jump start it, with the choke fully engaged, that's what's getting me the 4-4.3V. That's got to have me at 2k RPMS, right?

Doesn't seem to be any loose connections, frame is still bare metal, so no paint interference.

 

So I checked with a little more revving and as I rev more, the voltage drops down to about 3V.

 

Then next thing is to check the regulator, should be instructions for checking it in your service manual.

 

Because I suck with a multimeter, checking those two things has proved tough. As a side question, would either of those going bad directly result in it becoming tougher to start the bike even with a jump?? Or maybe indirectly, is it beginning to fry my starter? There's consistently a click, long pause, then everything begins to rotate...but that long pause concerns me.

 

I am no electrical expert but did you check stator?