charging circuit or battery ?

[nb1914]

Hi all,

Just a quick confidence check before splashing out, ok so my bike has been dying. I checked the battery voltage 11.3 which i know is no good. I charged the battery over night unto 13.5V then i left it over night and it went down to 12.6 then after leaving again for a day it went to 12.4/12.3. Im not sure how to check the charging circuit so i simply started her up ( battery now at 11.6v when running) and with a multimeter on the battery reved her a bit and i saw the voltage increase by approx .2v. In my mind the battery shouldn't drop voltage that much overnight (its the original from when i bought it ) and as i see some voltage increase when running is the charging circuit ok ?. I have converted the charging circuit with the nylon bolts and have fitted a modern combined reg/rec. Any thoughts welcome.

 

[retiredgentleman]

Your charging system should increase the battery voltage to about 14.1 volts when you rev the engine to 3000+ rpm. How high did you rev the engine?
What components did the stock charging system have? Did it have a combo unit or did it have separate rectifier and regulator?
Your battery may be OK. It would have to have a load test to see if it is in good condition.

 

[nb1914]

The original reg/rec were individual items but not the originals someone must have upgraded in the past, i didn't rev it too high ( no rec counter) i will post a diagram of my electrics soon as i completely re-wired so highly possible i messed up somewhere. Previously to this i did go on 2 short rides of approx 5 miles each without charging the battery with no issues at all bike ran perfect, on the 3rd ride after approx 4 miles it died started died etc.

 

[retiredgentleman]

There are 2 types of charging systems. In north america, the 1970 to 1979 bikes used a ground (earth) on the inner, right side brush. The 1980 to 1984 bikes had both brushes isolated from earth. The UK may be different.
The combo rec/reg you now have should work if its designed to work with both brushes isolated from earth. However, if you have the other combo type that needs an earth, then it won't work with the nylon screws.

 

[nb1914]

This is the only info i have on the reg/rec, would it be safe to simple convert the brushes back to all brass screws to see if it has an effect or could that toast the reg/rec if its wrong.

Direct replacement to your original unit
Plug-and-play, direct fit, easy installation
Higher grade of electronic components
Improved heat sink and charging capabilities
Quality exceeds the OEM equipment
heavy duty regulator/rectifier replaces OEM part
100% Brand New
Easy to install, No Installation Instruction
Fitment:
Yamaha XJ550 1981-1983
Yamaha YX600 1986-1988
Yamaha XJ650 Turbo 1980-1985
Yamaha XS650 1978-1983
Yamaha XJ900 F 1983-1994
Yamaha XJ700 1985-1986
Yamaha XJ600 1984-1992
Yamaha XS400 (D.o.h.c) 1982-1985
Yamaha FZ600 1987-1989
Yamaha XJ750 1981-1984
Yamaha FJ600 1984-1985

 

[weekendrider]

IMO this is a good representation of a charging system.
'77 stock displacement, Pamco igniton,'77 38 mm carbs, stock alternator, the solid state conversion for individual rec/reg, LED turn signals and headlight.
You will see it run under no load and full load (lights all on, not on, headlight only or turn signal only)
This charging system does run a bit higher than the original motor did but never goes to 15 volts, close but doesn't hit 15.
It starts climbing in out put as soon as you increase the rpm, and it tops out at a cut out point determined by the regulator and not necessarily dependent on rpm.
In other words sometimes it hits the 14,9x mark at 3K rpm sometimes at 4K. But who is to say it isn't a variance in the mechanical tach?
The original motor(bent valve motor) would top out at 14.4 but would have the same/similar voltage increase as demonstrated, only a lower top value.
As nothing was changed in the system other than the stock alternator I attribute it to the the alternator. They are the same but different.

Addressing your problem, it takes a good battery to run these. Your charging and small drop in the following days says your battery may be good. The fact you were able to ride for couple of times before it dying also is indicative that the battery is not at fault. An at home load test would be to install the battery charged and turn the headlight on bright, cycle the key/switch several times with the volt meter checking the battery for on/off voltage. Now leave it alone for an hour or two. A good battery should recover to almost full charge. If you have a dead cell(s) or weak cell(s) it won't. Check your brush length. Check the rotor ohms. Then move on down the system to the rectifier and regulator. Then wiring for a short that is draining the battery. Best I have to offer without actually being hands on.

 

[nb1914]

I will try the load test somehow as i have no lights ( you can get an MOT in uk without them) I am wondering now if should have altered the charging system with nylon bolts as the spec sheet does state "replace without modifications" the brushes on the rotor are new, i will check again but i think i saw 7ohms on the rotor.

 

[5twins]

I've found that peak output will vary depending on battery charge. A check immediately after starting with the electric start will often show a higher peak output, like WER's 14.9, compared to a check after a ride and after the battery is fully replenished. Then he may only see in the low 14's.

 

[retiredgentleman]

This is the only info i have on the reg/rec, would it be safe to simple convert the brushes back to all brass screws to see if it has an effect or could that toast the reg/rec if its wrong.

Direct replacement to your original unit
Plug-and-play, direct fit, easy installation
Higher grade of electronic components
Improved heat sink and charging capabilities
Quality exceeds the OEM equipment
heavy duty regulator/rectifier replaces OEM part
100% Brand New
Easy to install, No Installation Instruction
Fitment:
Yamaha XJ550 1981-1983
Yamaha YX600 1986-1988
Yamaha XJ650 Turbo 1980-1985
Yamaha XS650 1978-1983
Yamaha XJ900 F 1983-1994
Yamaha XJ700 1985-1986
Yamaha XJ600 1984-1992
Yamaha XS400 (D.o.h.c) 1982-1985
Yamaha FZ600 1987-1989
Yamaha XJ750 1981-1984
Yamaha FJ600 1984-1985

Well, you appear to have the north american 1980 to 1984 type of rec/reg. So that is good to work with nylon screws.
Show us your wiring diagram, so we can see if its correct. Do not go back to steel screws until we see your wiring diagram.

 

[5twins]

From the description, your new reg/rec appears to be the later style ground switching type. Whether you need to use the nylon screws or not depends on which brush mounting configuration you have. If you have the '79 and earlier brush set-up then yes, you need the nylon screws. The inner brush on that set-up is permanently grounded through it's mounting screws. You need to isolate it from ground so the regulator can control the grounding. It does so to the other (outer) brush. There is one more change you must make. You have to supply switched power to that inner brush that was previously grounded through it's mounts. Just adding the nylon screws won't make your late style reg/rec work. That's only half the job. You have to change the wiring to the inner brush too.

 

[nb1914]

Ah 5twins, i didn't make any changes other than use the nylon screws on the inner brush……..i didn't change the brush wires around , i will upload a diagram soon but i suppose it could simply be the wires swap i need ??

 

[5twins]

Yes, that could be it. If you have the early brush set-up and you didn't change the wire to the inner brush, the alternator is not being fed any power now, just ground. Previously, the power was fed in to the outer brush from the old regulator. Your new regulator doesn't feed power in, it does ground.

 

[nb1914]

I havnt got a photo to hand of the brush setup but I'm sure its the early version i.e. the inner brush is fed from the top left to bottom right with the metal plates, the bottom left i.e. outer brush is on its own. Below is my wiring diag currently without swapping the brush wires i have wire connected to the positive rail after the ignition switch which is connected to the top left brush screw ( inner brush ) i have a green wire from RR connected to the bottom left ( outer brush ) would it be a simple matter of connecting the green from RR to inner brush and positive feed to the outer brush.

 

[5twins]

If you have it wired the way your diagram shows then it should work, no need to switch the green wire to the other brush. You want switched power to the inner brush, switched ground from the regulator (green wire) to the outer. If it's wired that way and you have the nylon screws in place, and it's not charging, the brush wiring isn't the problem, it's something else. Check that rotor again, 7 ohms isn't good. It should be more like 5.

 

[retiredgentleman]

7 ohms is a little high. Connect both leads of your meter together, with lowest ohm scale. What does it read? It could be as much as 1 ohm. Subtract that reading to get the true rotor winding resistance.
You should also check the resistance from either slip ring to the frame of the rotor. Remove the brushes and use a high ohms scale to measure. It should read a very high resistance.

Are the slip rings looking all dull. If so, you need to clean them with some very fine emery paper. You want to see them with a very bright copper finish, so that the resistance is low.

 

[xjwmx]

Have you found "Curley's charging guide" yet? It's very helpful. It is about tracing charging problems down methodically, step-by-step.

One thing to do is oepn all the relevant connectors, spray them good with electrical contact cleaner then silicone dielectric grease them. This includes the connector inside the headlight that comes from the ignition switch. If any voltage coming out of the switch is much lower than the battery then you'll need to take the switch apart and clean the contacts.

The battery doesn't sound too bad. It went up 0.2 volts when you revved it which implies the circuit is ok. If your voltages are ok, then your components are bad. If the voltages are bad, correct it and try again. Pretty simple. Checking voltages with components disconnected can help find bad components, in cases where you can't just test the component.

 

[nb1914]

I re-measured the rotor resistance, i get approx 5.8ohms so i guess not too bad and approx 9ohms measured between the brush contacts. I will look for that guide but i guess I'm down too pulling the loom apart to check battery is still dropping voltage slowly.

 

[nb1914]

just out of interest what would be the effect if say 1 or 2 of the 3phase wires from the stator were disconnected ? would there still be a slight charge, i ask as i had to join these using crimps and couldn't see anyway easily to check continuity.

 

[5twins]

Your charging system should put out about 2 volts more when revved than at idle. It doesn't matter what your battery is reading at idle, rev the bike and that should go up about 2 volts. Yours doesn't seem to do that.

 

[nb1914]

yip i only get approx 0.2volts i.e. goes from 11.6v to 11.8v not quite sure what that might indicate but firstly i will re-check the wiring, is there away to check whats coming off the stator when disconnected from the RR ?