Question about alternator brushes ?
Moderators: oldjapanesebikes, H2RICK, diamondj, Suzsmokeyallan
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Question about alternator brushes ?
If they crack, are worn, etc. What is a common electrical characteristic that they are in need of being changed ? Does the bike simply not want to hold a charge, won't start, does the bike buck ( surge or cut in and out of electrical power), lights are screwed up ? I have 2 sets of new brushes and I may just replace the original ones on my restored bike to eliminate that as one cause for a couple of small electrical problems I am having. And just to replace them. The originals seem to have a lot of meat to them. Don't appear cracked. Is there a gap you need to set with them or simply install them and be sure that they are seated against the rotor shaft ? One of the small electrical problems I having is the bike has a brand new sealed battery ( I tested it ) and a brand new combined rectifier/regulator and doesn't want to hold a charge. The rectifier/regulator is grounded to the battery box. The battery box has a very light coat of fresh paint. But, the ground terminal is fastened with a brand new stainless bolt and washer. Could the new paint under the fastener be affecting the ground ? I wish I was good at diagnosing electrical problems with an ohm meter. But, I know nothing about using one. But, testing a battery. I'm confident I'll sort it out though. Just need some advice.
- oldjapanesebikes
- Moto GP
- Posts: 3229
- Joined: Sat Feb 07, 2009 12:43 am
- Country: Canada
- Suzuki 2-Strokes: GT750(Jx3,L,M,A,B),T500
- Location: Ontario
- Contact:
Re: Question about alternator brushes ?
That's a long list of questions and I'm sure jabcb will be along presently
but basically the only issues I've seen with the brushes is that they eventually wear away to nubs and need to be replaced.


- - there is no clearance to be set - they have to be touching the commutator to work
- - have you checked to see what the output is is at about 3500 rpm ? If not, then with everything hooked up, and with your lights on take a voltage reading at the battery first with the engine at idle, and then with the engine at about 3500 rpm. If you see the voltage change from about 12.4 v to something around 14.3 v then the charging circuit is working and you need to look elsewhere
- - for grounding checks - with your ohm metre, check the reading between the battery ground (I'd disconnect the battery first) and the furthest points in the harness - so in the headlamp bucket, at the engine case and at the tail lamp. If you see zero ohms, then you are probably OK

Ian
If at first you don't succeed, just get a bigger hammer !
If at first you don't succeed, just get a bigger hammer !
- jabcb
- Moto GP
- Posts: 4318
- Joined: Mon Dec 13, 2010 4:32 pm
- Country: USA
- Suzuki 2-Strokes: 69 T350 thru 75 GT750
- Location: southwestern Pennsylvania
Re: Question about alternator brushes ?
Brushes provide the electrical connection to the field coil, so they have to be in good contact.
A crack in a brush can interfere with the current flow within the brush, so that can be an issue too.
Replacing brushes that work ok is optional:
1) you can keep the spares for later use, or
2) replace them now so that you don't have to do it for a long time
The rectifier/regulator has to have good connections to the bike's positive circuit (battery +) & to ground.
If the ground isn't good, it will just reduce the alternator's output to get what it thinks is the correct voltage.
With the bike running above idle (something like 3.5k rpm is fine):
1) check the voltage across the battery
2) check voltage drop from rectifier/regulator positive wire connector (red wire) to battery positive
3) check voltage drop from rectifier/regulator negative wire connector (black or maybe brown wire) to battery negative
A crack in a brush can interfere with the current flow within the brush, so that can be an issue too.
Replacing brushes that work ok is optional:
1) you can keep the spares for later use, or
2) replace them now so that you don't have to do it for a long time
The rectifier/regulator has to have good connections to the bike's positive circuit (battery +) & to ground.
If the ground isn't good, it will just reduce the alternator's output to get what it thinks is the correct voltage.
With the bike running above idle (something like 3.5k rpm is fine):
1) check the voltage across the battery
2) check voltage drop from rectifier/regulator positive wire connector (red wire) to battery positive
3) check voltage drop from rectifier/regulator negative wire connector (black or maybe brown wire) to battery negative
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more
Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Re: Question about alternator brushes ?
Thanks, guys. I'm gonna do that test within the next few days. I may be back for more questions. Even though, Ian says I ask too many. Lol ! 

- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Re: Question about alternator brushes ?
One other small thing to consider is the earth from the frame on the battery box bolt to the electrical panel. Considering what its job is, I made up some new ones for all my Buffalos. For excellent continuity and no corrosion issues, I used larger gauge wire and gold plated eyelets on my upgraded parts.
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Re: Question about alternator brushes ?
Ok, Allan. I purchased a new Suzuki Oem ground wire that you speak of. The current version is a heavier gauge than what was originally on the bike. The eyelets are also made of brass. Unlike the original. If I remember correctly it's eyelets were zinc plated. So, I believe that quality of new ground is good. But, It may help to scratch away some paint under it's ground surface ? I also added electrical grease.Suzsmokeyallan wrote:One other small thing to consider is the earth from the frame on the battery box bolt to the electrical panel. Considering what its job is, I made up some new ones for all my Buffalos. For excellent continuity and no corrosion issues, I used larger gauge wire and gold plated eyelets on my upgraded parts.
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Re: Question about alternator brushes ?
The eyelet goes between the bolt head and the washer on the rear left side of the battery box fitting, so you only need to run a tap through the threads on that bolts location to clean them and add the electrical grease. Theres no need to scrap any paint off of any surface.
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
- oldjapanesebikes
- Moto GP
- Posts: 3229
- Joined: Sat Feb 07, 2009 12:43 am
- Country: Canada
- Suzuki 2-Strokes: GT750(Jx3,L,M,A,B),T500
- Location: Ontario
- Contact:
Re: Question about alternator brushes ?
Certainly it won't hurt, but the ohm metre will tell you.pearljam724 wrote:But, It may help to scratch away some paint under it's ground surface ?

Ian
If at first you don't succeed, just get a bigger hammer !
If at first you don't succeed, just get a bigger hammer !
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Re: Question about alternator brushes ?
Well, I swapped out the new rectifier/regulator single unit for a few year old separate rectifier and regulator off my 550 and it cured the problem. Held a charge on a 4 or 5 hour ride. When I began the ride, the battery was nearly dead for being drained from the new rectifier/regulator solo unit. I'll have to inspect the wiring on the new unit, but I'm pretty sure I already did that. I think the new solo unit ain't worth a damn. I bought the single unit from a Hong Kong seller on Ebay, I believe. the cost was $40. Turns out it's not worth a buck. 

-
- Road race school
- Posts: 841
- Joined: Tue Feb 19, 2013 2:45 am
- Country: Australia
- Suzuki 2-Strokes: Suzuki GT750A 1976
- Location: Sydney New South Wales
Re: Question about alternator brushes ?


GT750Battleship.
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Re: Question about alternator brushes ?
Sorry to hear about your failed product thats a problem you can do without for sure.
I've got both systems, the stock rectifier and some of the standalone regulators from Anthony at Oregon Motorcycle. I've also got one of his regulator/rectifiers he made as well but have not mounted it on any bike.
Since the GTs electrical panel has places for the two units I just like the idea of keeping them separate.
If you have the old rectifier and its good then you only need an electronic regulator from Oregon Motorcycle, its got a guarantee which is even better.
By the way its got a pot on it that adjusts output voltage, I believe its around 1/2 volt range.
http://oregonmotorcycleparts.com/vregulators.html" onclick="window.open(this.href);return false;
I've got both systems, the stock rectifier and some of the standalone regulators from Anthony at Oregon Motorcycle. I've also got one of his regulator/rectifiers he made as well but have not mounted it on any bike.
Since the GTs electrical panel has places for the two units I just like the idea of keeping them separate.
If you have the old rectifier and its good then you only need an electronic regulator from Oregon Motorcycle, its got a guarantee which is even better.
By the way its got a pot on it that adjusts output voltage, I believe its around 1/2 volt range.
http://oregonmotorcycleparts.com/vregulators.html" onclick="window.open(this.href);return false;
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Re: Question about alternator brushes ?
Thanks, for the references. Slowly, I'm sorting out the last couple small electrical bugs. I think it will help if I solder the leads on the RexCaunt coils, so that I can use them. All signals were working, but both on the left side stopped. The big thing was holding a charge. Which I think is accomplished. The bike is running fantastic though. Pulls very hard up to redline. The loss of weight from the chambers is very noticeable flicking the bike around. A throttle mod I did and a gearing change has made it into what seems twice the bike it was before I started the tear down. It's quite peppy now.
-
- AMA Superbike
- Posts: 1681
- Joined: Tue Jul 24, 2012 11:45 pm
- Country: U.S.
- Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
- Location: SW PA
Re: Question about alternator brushes ?
I think I found the problem with new rectifier/regulator single unit. I triple checked all mating wires, ground, etc. Today, I removed the pins from the 2 sockets on the new unit. Very oddly, the exterior and the latch are identical to the original sockets. However, when I removed the pins. I noticed that these sockets have a 3 or 4 millimeter protrusion of plastic sticking out past the hole where the pins slide through on the interior. These sockets on the new unit are designed that way for whatever reasons. Unlike the original sockets. I'm thinking that this is causing a bad connection on the male and female pins because they aren't allowed to make compete contact through the complete distance of the pins. So, I threw those in the garbage and swapped for the original sockets on the separate rectifier and regulator that came off my 550. I believe this should fix the new unit. But, I won't know for sure until I take it for another ride sometime in the future.