So I finally got my bike running and on the road after years of working on it. Battery was fully charged and I put about 2 hours in a parking lot on it (learning to ride) before parking it for the night. Day 2, I got another hour before the bike stalled while I was stopped in neutral. I didn't have enough power to restart. After getting the bike jumped and back home I did some tests.

When my radiator fan turns on the rpms drop drastically and the bike will stall. Now I can counter this with a higher idle. I am currently about 1k rpm. Is the alternator/generator bad? Replace the battery? Or is my RPM just too low and can't compensate for the increased electrical load?

Please help as I don't want to blindly replace parts only to be left stranded if it dies again.

 

Idle of 1000-1100 rpm is fine, what voltage are you seeing on the battery, should be 13 to 14.5 volts when revved, if not your regulator rectifier may be on the way out and not charging properly.

 

At idle it was at 11.9-12.0. When I turn the high beam on and the turn signal it drops to around 11.7-11.8. When the fan kicks on with the other stuff on it goes to 11.5 and dies. I will try to warm it up tomorrow and get a voltage when revved.

 

I would also load test your battery as anything less than perfect can cause troubles.

 

The 1000F alternator doesn't start charging (using the standard regulator/rectifier) below 3000 revs. Riding these bikes slowly around a parking lot will not push enough current into the battery to keep the bike running after a while, especially if you're running the lights at the same time.
If you plan to do a lot of slow speed (and low revs) I'd suggest you fit an aftermarket reg/rec - I have one from Electrex which starts charging at around 1400RPM and gives you slightly higher input (up to 15.5V) at normal running.
If you were to take the bike out onto a road and run it normally you would not be having a problem.

 

So charged the battery for 24 hours roughly and running voltage was 13.5 or so and slowly dropping. When revved above 3,000 rpm it goes to 14.4-14.5 volts.

Shadow - Thanks for the insight. I never would have thought that the regulator would not allow charging below 3k.

I will just have to do loops in the parking lot at lower gear and higher rpm so I can keep learning. I would prefer to learn in a controlled envirnoment than on the street with all sorts of other things.

Thanks very much for the help guys.

 

Always a pleasure to help.

Just remember - higher revs at slow speed equals overheating, which in turn will spin the fan, which will munch your battery.......
There's not really a happy medium unless you can find a bigger parking lot.....

These bikes were never really designed to learn on - they are high speed touring bikes that don't like high volume traffic or too much slow, lower gear riding.