Bike:
1999 Yamaha R1

Problem:
When out riding sometimes my battery dies. I hooked up a digital volt gauge to see whats happening and this is what I found.
At idle the volts sit at 12.0v then randomly will climb to 13.5v. Then the voltage will stay the same when I rev up, even above 5,000 rpms. Then when I let off the throttle the volts drop all the way back down to 12.0v- very strange

What I've tried:
(all tested good but replaced them anyway)
replaced the battery, the Stator, the rectifier
The main ignition (key) switch (had a short thanks to some *** hat wanna be bike theif)

The bike acts the same way after replacing all the above items. help please! why would voltage drop after I let off the throttle and not raise at above 5,000rpms?

 

Check your wiring harness's integrity. Check all the leads right at the stator connection and at the rec plug end for continuity. Sounds like you have a bad wire somehwere. Did the old reg/rec look deformed from heat at all? When they go bad I have seen some short a wire. Also make sure all the pins are tight in the connector, sometimes they can be pushed out and loose contact if they are bent a little bit.

 

I checked the harness today. everything looks good and all connections are tight. Each part on its own test good. yeah the old rectifier had a slight burn on the RR plug so I replaced that along with the RR and it wasn't deformed or anything

 

my battery doesnt charge either.

i push start my bike.

its been like this for about a week, ill prolly go to walmart tomorrow to get me a new battery.

 

I found the problem. My flywheel bolt came loose again! grrrr! the crank shaft doesn't have aplace for a key to lock the flywheel to the crank so I think thats why it came loose again.