Some help with my Yamaha - Alternator

[crayonjota]

Ok, so the long and short is that my Yamaha FZR600 charges just fine below about 7000rpm, but after a good long hard caning the battery is discharged.

I tested it out with a voltmeter on a discharged battery. I push started and had a base figure of 11.3v on the battery. At idle, with lights on (I had tried disconnecting the lights to save energy..) the voltmeter read 12.4 at 6000rpm a steady 13.8 and at 10,000 back to less than 12v.

By eye you could see the light on the wall. at idle it was dim, then as the revs rose it got brighter and brighter till it dimmed to almost nothing after the 7000rpm threshold.

I have the shop manual and I ran all the diagnostics it describes, but doesnt have anything for this problem.. I am thinking perhaps brushes on the armature?

Anyone with a clue?

CJ

[Dink]

Sounds like a short in one leg, revs are breaking the connection.
Try resistance testing at the same rev points

Dink

[Boondocks]

Ok, so the long and short is that my Yamaha FZR600 charges just fine below about 7000rpm, but after a good long hard caning the battery is discharged.

I tested it out with a voltmeter on a discharged battery. I push started and had a base figure of 11.3v on the battery. At idle, with lights on (I had tried disconnecting the lights to save energy..) the voltmeter read 12.4 at 6000rpm a steady 13.8 and at 10,000 back to less than 12v.

By eye you could see the light on the wall. at idle it was dim, then as the revs rose it got brighter and brighter till it dimmed to almost nothing after the 7000rpm threshold.

I have the shop manual and I ran all the diagnostics it describes, but doesnt have anything for this problem.. I am thinking perhaps brushes on the armature?

Anyone with a clue?

CJ

I don't know what type of alternator you have. If it's a permanent magnet type like on the GS, it won't have brushes. If it's a field coil activated alternator, it will have brushes and slip rings.

Don't worry about finding some diagnostic that matches up exactly with the electrical behavior. Use your shop manual to test the alternator and R/R separately. The alternator will probably be tested by checking the AC voltage with the stator wires disconnected from the R/R. On the Suzuki GS models, OEM and aftermarket stators should have equal AC voltage output on all three stator legs. Depending on the stator design, this might range from 50 VAC (some aftermarket) to 80 VAC (OEM) or so. The test on GS models is performed at 5,000 rpm.

If the alternator checks out OK, you probably have a bad R/R. Check it according to the procedure in your shop manual.

[crayonjota]

Sounds like a short in one leg, revs are breaking the connection.
Try resistance testing at the same rev points

Dink

I do have one leg shorter than the other, as it goes, something about a couple of months in traction...

Seriously though. Thanks.. I will drag off some plastic and take a rusty screwdriver to the alternator tomorrow. I dont think its a 2stage job though, like on the GS..

CJ

[crayonjota]

I figured it was only fair to come and give the diagnostic.. Thanks again for all the help.

Word is the brushes or springs/clips that hold them pressed to the armature are suspect.. So it should be cheap to fix. I lilke that..

CJ