Idle gets choppy when fan kicks on

Hey guys, does anyone know what might be the cause of my idle getting really choppy when my cooling fan kicks on? It starts to stumble alot and comes close to dying. I was thinking maybe it's in the charging system, not sure if the brushes in the generator have ever been changed. What's the best way to check the charging system? Should I just physically look at the brushes and see if they're warn? Oh, my battery is also pretty much dead, I have to jump it every time to get the bike started, so could that also be a possible cause?

Oh, this is on my '85 XJ700X.

Thanks.

P.S.

I know the battery probably should of been one of the first things I replaced, but the bike was in rough shape when I got it. I just now got it running, and got everything back on it. Which is why I haven't replaced it yet.

 

Sounds like it could be your battery. The bike runs off the battery until about 2k plus rpm. Take the battery down and have it tested. Also go ahead and check your brushes it's easy enough to do.

 

Thanks, will do.

Any suggestions on where to get a new battery if I need one? I've heard they're kind of pricey. Haven't actually looked around much though.

 

for the brushes I believe the wear limit is 10mm from the line on them.

Ditto on the battery these bikes have to have a good battery to run properly. I just got my X back together a little before winter and have a few things left I want to do on it as well.

 

Another thing you could try is hooking up a 6A or so battery charger while running the bike through a warmup cycle. If having the battery charger hooked up eliminates the idle problem, then at least you know the issue is likely being caused by low supply voltage, rather than something else, like electrical noise, interference, or just plain high temp.