CB500 Charging issue - Is my rectifier duff?

[Cyclingbiker]

I have my first big bike now after passing my test last year. It is a 1999 Honda CB500s (with the half fairing) in yellow, the bike is in fairly good nick for its ages some chips and scratches plus a hole in the silencer that could do with welding up at some point. The bike runs well and is sooooo much faster than my 125, even at 33bhp.

The only issue I'm having is with battery charging. Basically the bike will run forever with no lights on or just the sidelight on, but as soon as I put the main or hi-beam on it will drain the battery very quickly. The bike will run but won't start again if I switch it off, the battery will be flat or very nearly so. This doesn't happen unless I have been running the main beam though.

I have suspect a duff rectifier and have my Haynes manual to help me test it. So far I taken the battery from the bike and charged it up to capacity with a trickle charger, I left it on all night and by the morning it showed a steady 12.9 volts once it had been disconnected from the charger for a few hours. It was then hooked back up to the bike to test for rectifier output with my multimeter.
In the Haynes it asks to start the bike and switch the Hi beam on, the bike is supposed to run a 60/55w H4 bulb and I can confirm that it has one fitted. There are no other power-draining accessories such as alarms or heated grips fitted to suck the power.

So with the lights on and the bike held steady at 5000 rpm I should be seeing between 14.0 and 15.5v on the meter across the terminals but I can only see a max of 12.7v and with any less revs it drops rapidly (within a few seconds) below 11v. This is why it is draining so quick I suppose.

Without any load on the system, all lights off, I do get the specified voltage across the terminals but not with the lights on.

Then I go to test the rectifier with the Ohms resistance scale on my meter. The Haynes has a small diagram of the 5 pins on the rectifier marked clockwise from bottom-left "A-B-C-D-E". B-C-D are the input from the generator and A-E are to the battery and earth respectively.

https://cdn.bikechatforums.com/files/rectifier.png

What is confusing me though is that I only get the specified readings with the polarity of the leads reversed! So that when I should be getting those readings with the positive lead on "A" and the negative lead on one of the others I get no continuity. It is only when I put the negative lead on "A" and try again with positive lead on the others that I get the readings I am looking for

Somebody help me out here, if is duff or not?
____________________
Honda CB500s (1999) - Honda CG 125 BR-J (1991)

Mod 1 - Passed - 12/11/12 --- Mod 2 - Passed - 26/11/12

[salem1987]

Reg/recs can be mysterious things in my experience. I had one on a cbr400 which would only fail once it got warm.
The cb500 one looks very similar to the one on the 400 when i look at mine. Its definitely worth getting one off an R1 or something if you do decide to replace it - Much better build quality and actually has cooling fins to keep it cool.

I also ended up fitting a cooling fan from a PC over the top of mine and wired it into the rear light, dunno if it worked but it added piece of mind at least!

Have you checked readings from the stator with your multimeter also?

[Cyclingbiker]

Yes I've heard that the Mosfet type from the R1 is preferred replacement for Honda reg/recs, a bit of research shows that they come up second hand for various prices:

https://www.ebay.co.uk/itm/Yamaha-R1-04-05-06-5vy-regulator-rectifier-/380706608196?pt=UK_Motorcycle_Parts_13&hash=item58a3e1d444

Or as part of a complete kit from the states for £70-80

https://www.ebay.co.uk/itm/SHINDENGEN-MOSFET-FH020AA-REGULATOR-RECTIFIER-KIT-REPLACES-FH012AA-/380704480069?pt=Motorcycles_Parts_Accessories&hash=item58a3c15b45

I have checked the resistance of the coils with the meter, the manual says it should be 0.18-0.2 ohms but I am getting something like 0.6 ohms between all three wire, there is no cotinuity to earth on any wire. It is outside of the specs but I don't know how much difference it makes.
____________________
Honda CB500s (1999) - Honda CG 125 BR-J (1991)

Mod 1 - Passed - 12/11/12 --- Mod 2 - Passed - 26/11/12

[stinkwheel]

Ignore that testing diagram. It will only work on a dynamic test with a particular type of ohmeter.

A normal multimeter doesn't use enough voltage to saturate the semiconductors in the reg/rec and you'll get all manner of weird readings.

The cances are, it's the reg/rec. Your bike is bang in the middle of the era when they were making dodgy ones and I know for a fact yours has one of the ones with absolutely no heat sinking at all because Mrs stinkwheel has the exact same model.

One other possability is if there is something causing a huge drain along with the lights. Repeat the test with the lights off and see if it's putting out your 14-15.5V.

If it's charging properly with the lights off, it would be nice to get an ammeter in series with the headlights and see how much current they're drawing. I'd be expecting somewhere in the region of 6.5 to 7.5 amps just from the lights. Bear this in mind because you'll fry a standard multimeter with this much current. Many of them will have a specific 10A input, this would be the time to use it.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Islander]

As Stinkwheel said, you'll need a specific type of meter with a semiconductor test function to get any sense out of it. A reading in one direction and not the other is normal for a semiconductor junction - that's what they do, pass current in one direction only.

Voltage checks are the usual way of finding out where the fault is.

[Cyclingbiker]

[WD Forte]

Yep that diagrams pretty useless for normal folk
You can test the RR with a bog standard cheapo dgital meter
If it has a diode test function, its even easier

First though, its always best to test the stator windings first
this is quite easy as wel.
l
Disconnect the plug from the RR
and set the meter to its lowest resistance/ohm range
Short the probes together and note the reading, this is usually less then 1 ohm.
Next read the resistance between each of the 3 yellow wires from the stator, you should get very low readings of about 1 ohm or less
taking into account the meter lead resistance.
next read the resistance between the yellow wires and ground or battery negative.
You want to see very high resistance here, megohms or off the scale.
If it all checks out fine then you can move on and test the RR, if it doesnt you probably need a new stator.

Testing the RR
disconnect it from the rest of the bike
Set the meter to diode test and put the red probe on each pin which connects to a yellow wire from the stator and the black probe on the pin the red wire goes to.
You want to see about 0.5 on the display each time

Next put the red probe on the green wire (ground) pin and the black probe on each yellow in turn.
Again you want to see 0.5 on the display
If it all checks out well, the rectifier is probably OK
but voltage regulation can only be checked when its running
Check all cables and connectors as well for damage and scorching
Ideally, you want to see about 14-14.5v across the battery when the bikes running, lights on or off
HTH
____________________
bikers smell of wee

[stinkwheel]

[cb1rocket]

You could put a heat sink on it from a CPU cooler etc ?
____________________
Honda H100S2 Rebuild - https://www.bikechatforums.com/viewtopic.php?t=253852

[Islander]

[Robby]

Either replace with a MOSFET one that will last, or replace it with another cheap one and hope. Fitting a PC fan may help a bit, but the chances are that the little fan will have failed due to dirt or vibration long before the reg/rec is due to expire - the current one is anything up to 15 years old after all.

Make sure the replacement has good clean mounting points to sit on, and good clean connectors in the connector block. Clean connections mean the new reg/rec has an easier time and will last a bit longer.

[smegballs]

I put a shindegen FH001 on my sisters ZZR600 a few years ago had no charging problems since. IIRC "FH" in the shindegen model number means that it is a mosfet model.

[Cyclingbiker]

Cheers guys this is now (Hopefully) sorted for good.

I ended up with a MOSFET rectifier from a BMW S1000rr that I picked up from a German breakers on eBay for £65 posted. It is specifically a Shindengen FH012DA.

For connections instead of buying those blocks from the states I went off a tip from many of the Triumph forums' threads on rectifier upgrades following a recall for some models fitted with shunt-type rectifiers. There is an official link lead sold by triumph for these upgrades with the part number T2500676

https://www.triumphrat.net/memberalbums/data/837/FH012_adapter.jpg

The 2-pin plug had the wires removed and set aside for a later date when I can fit the unit a little more permanently and so I untaped the two sets of wires so I have no excess wires in the tight space behind the LH panel of the bike. The 3-pin plug is the input from the genny and plug at the other end matches the plug from the stator but lacks the locking pin so I'll need to get that rectified fairly soon but for now it is going nowhere. I have removed the two battery wires from the old rectifier block and fitted the + and - spades directly to the pins on rectifier, it is not ideal but will do for now.

The battery is a little discharged at the moment but I was still getting a steady 12.5v at idle with full beam with a slow rise over the course of a few mins. At 5k rpm the voltage was up past 13.5v with high beam on and 14v without. I will be having a good ride out tomorrow and so the battery will get a good top-up.
I've just had a good 20 min ride in the dark with lights on and all is well so far

Did have an unrelated issue earlier as I was about to take the bike out for a test rise. The sidestand switch had developed at fault and was intermittently cutting the engine even with the stand up and the bike in gear so I had to bypass it for now with a piece of wire bridging 2 of the 3 pins and held on with insulating tape. I will get a new switch or permanent bypass sorted ASAP.

Also found out headstock bearings need replacing too as they are knocking slightly and have a notchy feeling to them
____________________
Honda CB500s (1999) - Honda CG 125 BR-J (1991)

Mod 1 - Passed - 12/11/12 --- Mod 2 - Passed - 26/11/12