Bad Battery Or?

[K_Flyer]

Thought my battery was dead. Just get a buzzing sound when I tried to start. Replaced the battery after quite a hassle. (Another thread) Rode the bike 156 miles last Friday including four starts with no problem. Went to start the bike this morning to get a new rear tire. Same buzzing sound. ;-( Thought I somehow developed a loose connection. Took it all apart, made sure everything fit well. Same thing. Used a voltmeter on the battery screw terminals. Voltage drops to zero when I try to start. Bike on center stand and in 5th gear,push on the tire it move and you can hear the cylinders move. WTF?

 

[RossKean]

Get it load tested. Might be a bad one. If it was just dropping to a low voltage (i.e. 9V or so), I might suggest looking at the starter solenoid and starter motor. Zero volts suggests essentially open although it might show 12+V as long as there is no draw.
Of course, you need to make sure that cables are securely connected but you are measuring on the actual terminals?
(I have seen a case where the vinyl cover from the positive cable got tucked between the cable and the terminal preventing solid contact.)

You're not having much luck lately!

 

[K_Flyer]

Have to take the battery out to load test it as there is almost no access to the positive terminal with the load tester.

Trying some other tests first. Now suspect the alternator.
Some other data points. Installed the new battery, put it on the tender, Removed tender and went for a ride (156 miles, four starts), got home and parked the bike. Two days later, it would not start. put the bike on the tender part of the day and it started normally. No time to ride for a couple of days. For grins, tried a start and it worked but to busy to ride.

The battery on its own went from 13.17V to13.05V in 24 hours and no drop in 5 more hours so the battery sounds okay. Setting up to measure drain of all "loads" on the battery when switch off. Then will check charging voltage with everything connected and vary loads; Moto Lites on/off, lights high/low. What should the minimum charging voltage be at idle?

Interesting that my riding buddy who restores Broncos guessed the alternator as the base problem.

 

[RossKean]

Check system voltage. Start bike and rev to 3,000 rpm or so. If the charging system is bad, there will be little difference with engine running. (Should get 14V or so running.) You then need to narrow it down between the stator and the regulator/rectifier. (Or a bad connection somewhere along the way.) Measure the AC output on all three stator legs - should all be the same. Can also measure the resistance of the three legs - should be low and the same as each other.