Electrical Issue

Hey guys, please help me understand my electrical issue. I have an 81 XJ550R that I now have running pretty good mechanically, but Im running into a strange electrical issue. New battery, fully charged. Good readings with the bike off (12.4V or so). When the bike is running, it makes my handheld Voltmeter flip out! It very quickly flashes randomness on the screen, never giving any kind of read. The strange part, I dont even have to get the prongs on the terminals, I can be within 5 or 6 inches of the bike and it wigs out. With the bike off everything is back to normal. Anyone ever heard of this? I replaced the rectifier/ regulator with a brand new one, same thing. Thanks guys!

 

how long have you had the meter? what brand? if you just purchased it it would return it.
Telsa would love this problem.

you are trying to read DC correct?
12.8 would be better battery off the bike.

what does the volt meter in the cluster do?

I would clean the vr connectors and ohm out the entire charging system.

make sure your grounds are clean the ones at the coil mounts the one to motor and the one from motor to frame.

 

Yes, DC. Im gonna check and clean all my grounds. I have a feeling Im not grounded properly. The meter in the cluster jumps around a bit when its revving too. Not near as wild as the handheld meter though.

 

ok . meter should climb with rpm and at 2k rpm be in the 14 volt range.

could be bad brushes in the alternator

 

Thanks for your help, I will check the brushes too

 

The frustration continues... So far Ive replace the rectifier, checked and cleaned all my ground cables, replaced the stator coil, replaced the brushes, and checked all the wiring and harnesses. Same thing, no charge at all. Like its completely disconnected. Battery is 12.6 when bke is off. Start it and it drops to about 12.2V and stays there no matter what rpm. I guess the only thing left is replacing the actual stator armature.

 

The field coil or rotor should measure 4.0 ohms +/- 10%. Did you measure this at the brown and green 2 pin connector just to be sure you have good contact at the brushes to the field coil?

If it ohms out OK (a little high at the connector is usually OK), then hook it back up, place a thin feeler gauge about 1/8 inch away from the alternator cover, turn the key to "ON" and the magnetic field from the field coil should pull the feeler gauge toward the cover.

Next, with everything connected and with just the key on and bike not running verify 12V at the brown wire and less than 1.8V (but not zero) at the green wire.

 

I once had a CB750 I bought from Dyer Honda hidden in their back room with 4500 miles one owner that passed away. Got 15 miles away 2 miles from my house and it died... battery dead after a quick charge ..I ordered a rectifier no help, went to Cycle Recycle 2 was ready to buy a stator...he told me it is the rotor. I was sceptical but went home , he handed me an axle shaft told me to thread it in end of rotor hit it several times 3 strikes it popped right off. Put new rotor , put it back toghether ,started bike up put volt meter on posts CHARGING like it should shazzam . Possible your rotor has went bad.

 

read this thread before buying a rotor look at before and after photos
charging system test reults

 

Measuring at the connector I am seeing 20.4 ohms. I haven measure directly on the rotor. Im going to clean up the contact rings and take a new measurement tonight. I will also try your other suggested checks. Thanks!

 

Thanks for the link. Im going to try to shine up the rotor rings tonight to see if that helps. Thanks!

 

Problem solved!! Took the stator cover back off and polished the contact rings of the rotor. Seems to be charging great now. Thanks guys!!