Alternator meter drops upon acceleration

[akinz]

I still need to do quite a bit on the bike, but I at least got it fired.... I am noticing a problem with the alternator meter. When the key is on and also idling, the meter shows approx. 12-13v (new Yuasa battery installed) but when the bike is revved, the voltage needle drops instead of rising. The bike only has 6400 miles on it. I purchased it from a previous owner who just purchased it at an estate auction.

I haven't pulled the alternator yet to see what condition the brushes are in. I know there is oil leaking between the two halves of the alternator, just wondering if anyone might have some insight as to what might be the problem.

Thanks in advance,
Kyle

[Rick Pope]

Do not run it until you have that oil leak fixed!

Most likely, the seal at the rear of the alternator is bad, allowing oil to get into the alternator, which should be dry. The oil will mix with the brush dust and create a conductive goo, wiping out components. When it happened to me, it took out every charging component, rotor, stator, and regulator.

The seal is a common one, available at any decent automotive parts house, as are the bearings. The bearing numbers are 6201 and 6203.

[akinz]

Yuck!, I was thinking that might be the problem, but was hoping it wasn't. Thanks for the info. So possibly the oil's wiped out the alternator etc. hence why the voltmeter drops when rpm's increase?

[Jeff Bennetts]

Yuck!, I was thinking that might be the problem, but was hoping it wasn't. Thanks for the info. So possibly the oil's wiped out the alternator etc. hence why the voltmeter drops when rpm's increase?

You may have lucked out, cln it up, use some fine emery cloth on the ring, replace the bearings and give it a whirl, or test it while its apart.

Do a search, plenty of threads here on it.

[Kool_Biker]

You have to fix the leak with no delay.

BUT, while at it, you must pay close attention to the alternator clutch plates, spring, washers, etc.
The drop you see in the voltmeter when you blip the throttle could be that as the (electrical) load increases, the alternator slips and hence the drop in voltage.

Good luck, Aris

[Rick Pope]

Sorry if I cause you any panic, both Jeff and Aris are correct.

The alternator is really simple. Take it apart, clean it out, inspect everything and re-assemble, using new bearings and seal. I can't recall the prices for the parts, but it used to be really cheap from a parts store, or >$50 from Honda. Are the Honda bearings better? Perhaps, but you'll likely need to have it apart again after 20k miles for new brushes anyway.

As Aris mentioned, do a search and find the thread explaining how to properly surface/shim the plates. It's not difficult. The hardest task you'll encounter is getting the bearing out of the outer half of the case, and that's easy too.

[akinz]

A lot of good points here that make a lot of sense. Unfortunately yes the bike only has 6400 miles but I believe it's been sitting so long that all the seals have hardened up and are causing a few oil leaks here and there. I'll look around for the resurfacing... I believe I've come across them before, but there was some speculation that getting rid of the grooves originally worn into the plates might cause more problems.

My experience with aftermarket oil seals has not been very good so I'll definitely plan to get all OEM parts.

Thanks for the help so far... once I crack it open and document it I'll be sure to share.
Kyle

[Jeff Bennetts]

What oil are you using, synthetic oil can make a marginal set of alt clutches and a weak spring slip under acceleration.

[akinz]

I'm using non-synthetic castrol 10w40. I just changed the oil when i got it.

[akinz]

castrol 10w40.

Motorcycle oil of course