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Marginal Charging...

Charging System, Wiring, Lighting
Maloymerc Member
Posts: 68
Joined: Mon Mar 05, 2007 3:50 am

Post by Maloymerc » Thu Jun 14, 2007 4:48 am

Hi Vince...
Can you tell how to determine if the magnet is already weak?
When i place a screwdriver beside it, it still sticks to the magnet but doesn't need much force to pull it this a sign of a weak magnet?

Vince Lupo Member
Posts: 1371
Joined: Wed May 04, 2005 7:17 am

Marginal Charging...

Post by Vince Lupo » Thu Jun 14, 2007 5:59 am

Hello Again -- Well of course I'm no expert (I just pay for the stuff!) but in comparing a new permanent magnet rotor from another bike (like a Triumph), it is not able to pick up a rather large wrench from the work table. That's really the only way to check (I don't know if there's a 'magnetism meter'). In reading Bill Silver's Honda Restoration Guide, he says that one of the reasons for a weak charging system is the loss of magnetism in the rotor. This is primarily due to age. He also mentions that 12.8 volts was about all you got out of the original system (more of a 'battery maintenance' system than a true 'charging' system). Also, I'm still trying to get an answer from the fellow at Jobmaster Magnets here in Baltimore, and while he's pretty sure he can do something in terms of remaking the rotor, I'm certain that he has much bigger fish to fry than making a little rotor for an old Honda, so that's why I think he's been dragging his feet on the issue. I did actually look at a new rotor for a Triumph to see if it is comparable, but it's too small and the taper is wrong. You could get a NOS rotor from Western Hills Honda or Ohio Cycle, but that might be a crapshoot too -- another 40+ year old rotor with questionable magnetism. If anyone has any other suggestions about this rotor stuff, we're all ears!

Maloymerc Member
Posts: 68
Joined: Mon Mar 05, 2007 3:50 am

Post by Maloymerc » Thu Jun 14, 2007 11:49 pm

Vince, i'd also like to mention that the wrapping that covers the copper wires on the stator have kinda peeled off, but from what the naked eye can see, there seems to be no damage or cut wires.

My question is...does this also affect the charging capacity?

Vince Lupo Member
Posts: 1371
Joined: Wed May 04, 2005 7:17 am

Marginal Charging...

Post by Vince Lupo » Fri Jun 15, 2007 3:11 am

Let me quote Bill Silver from his 305 Restoration Guide (which, once again, I heartily recommend for all out there -- even for those of us who pay others to do the work, like me!): "Problems occur (here) when a) a rotor loses its magnetism or b) the stator windings lose their insulation wrappings (usually from bad crank seals soaking the insulation, causing the insulation to fall off), then the coils begin to bounce around on their mountings, shorting themselves out to the grounded stator frame. Stator lead wires can also work loose and rub against the rotor or frame." Now, let me also quote from Mike Jackson, technical advisor with Classic Bike Magazine in the UK, who just replied to my charging query: "Modern (and that includes 1966!) magnetic materials do not lose their magnetism as readily as the pre-war ones did and I would not expect the low voltage on charge to be due to loss of magnetism. How have your mechanics determined that the rotor has lost magnetism? Rotors and stators from different manufacturers are not "mix and match" items so you can reject that line of thought. My suspicion is that the most likely culprit is the rectifier." The 'mix and match' refers to my thought of potentially using a rotor from another bike, like a Triumph. So, while one person says that rotors can lose magnetism, we now have someone else saying that it's unlikely. However, I am willing to give another rectifier a try. As for your dilemma, NOS alternators are about $ 400.00 or so, and I know that Western Hills Honda has some. The loss of insulation (according to Bill Silver) does in fact have an adverse effect. Hope this helps!

Maloymerc Member
Posts: 68
Joined: Mon Mar 05, 2007 3:50 am

Post by Maloymerc » Fri Jun 15, 2007 4:10 am

Thanks Vince, very informative indeed. I for one, would favor the latter reason as just being a rectifier problem. I may have to replace my stator due to it's disintegrated coil insulators as this may be a factor in the charging defficiency as cited by Bill Silver. I just called up a shop that fortunately has a NOS stator, rotor and rectifier...but very pricey. I'll try replacing the stator and rectifier first...might solve my problems.

fastjoe Member
Posts: 38
Joined: Thu Jan 04, 2007 2:14 pm
Location: kingman az

charging system

Post by fastjoe » Fri Jun 15, 2007 6:25 pm

l / lite sw
l l

diagram of how the 6 windings are wired as best i can do here.
this is a balanced system. meaning the alt output is equal to the load + maybe 0.5 amp for the battery. there is no voltage regulating other then the battery itself.
the bike runs on 1 pair of windings with lites off. the other 4 are taped in when the lite switch is turned on.
If the battery is good, the wireing is OK, the rectifier is new or tested OK, then low charging problem is most likely in the windings.
You will need a voltmeter, ohmeter and a trickle charger. apx 500ma / .5 amp.
read battery voltage , key off , just as it sits. should be around 12.6 if lower charge batt
hook up trickle charge, wait 10 min. read voltage --- you might see something like 13.2 apx.
you should see a similar voltage or more with the engine at about cruz RPM.
If not then move on to checking the windings.
find the 3 wires coming from th stator. use ohmeter , all should have continuity to each other but no continuity to ground. a short to ground is the most common problem. while checking for short try to wiggle each winding. sometimes they get loose and will have an intermitant short. I have fixed these by shiming with pieces of matchbook cover and sealing with epoxy.
trying to help

Maloymerc Member
Posts: 68
Joined: Mon Mar 05, 2007 3:50 am

Post by Maloymerc » Fri Jun 15, 2007 8:49 pm

Thanks Joe...this will help definitely!

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