Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Murf on September 04, 2025, 01:22:15 PM
-
I have just striped down what I would call the electrics plate, the plate with the rectifier, regulator, solenoid etc and have a couple of questions.
I have the original type regulator, electro / mechanical I guess. What is the general opinion are they ok and reliable or should I change it to a modern type, or go all the way and get a modern combined reg/rect.
Also what function does the starter safety box have.
Thanks.
-
The regulator in my experience rarely fails.
The starter safety box stops the starter operating unless EITHER the clutch lever is in OR the neutral light is on so it wont jerk forward if you press the button in gear
-
Rectifier, regulator and solenoid are maintenance free and live forever. A German engineer has substantiated that the OEM regulator is in practice better than a modern one, as its big resistor 'senses' the ambient temperature.
-
Thanks, that’s saved me some cash. Just need to get a new fuse box as that has seen quite a lot of heat at some point in its life, with a fair bit of melting around the highest amp fuse holder.
-
Go to the US site and look up Hondaman(Mark Parris) he makes a blade fuse type plug in fuse box
-
Thanks, that’s saved me some cash. Just need to get a new fuse box as that has seen quite a lot of heat at some point in its life, with a fair bit of melting around the highest amp fuse holder.
When you fit the new fuse box check the terminals inside the remaining half of the multi plug. It's quite common after a few years for the spade type connectors to turn green and create enough resistance for the ends of the fuses to get hot as they try to draw enough current. I had experience of a series of main fuse failures and I kept looking for a short circuit, until I was informed that if it's a 'short', then the fuse wire breaks in the glass, whereas in my case the end od the fuse had got hot enough so the end cap came loose.. Disconnect the battery and have an ejoyable 1/2 hour with a set of jewellers files. Have fun. Mike.
-
Hi Murf, after checking my connectors I found that the `green rust` had eaten in ssome cases half of the spade connectors (its easier to take the connectors out oif the blocks to clean, you can then see as in my case the bits you cant see like the half eaten terminal) so replaced the lot instead of cleaning, this was the safest route for me. its easy to take the terminals out and check.
-
Thanks
The little sub harness that connects everything together is definitely not in a great state and needs work. The wires of the 3 connectors to the regulator all have solder joints in them which look like they are about to break, so think I am going to put complete new wires and connections in to replace them, I have checked the spade connectors and surprisingly they are pretty ok.
It’s definitely worth putting work into this area of the bike as it looked like ‘break down central’ when I removed the plate with it all on.
Thanks Bryanj, I will check out that fuse box as it would be nice to upgrade to spade fuses.
-
All very interesting, but - as I am lazy - I prefer to perform a V-drop test before beginning tedious chores. If a test informs me V-drop is within limits, I'd abstain from activities not needed.
-
A v drop test? That might need some further explanation?
-
Well, if there's no V-drop over 0,5V - 1 V max, why would you start labour not needed? So far I never needed to clean connections.
If you're interested in what mechanics have to learn tp localise a bad connection, here it is.
It's just 4 steps with the same meter. When you look at the pics long enough, you'll get it. Realise that each picture depicts two (!)measurements. So the measurement on the left is the first, the one on the right the second and in the second picture the measurement on the left is the third, the one on the right the fourth step.
Let's say there's a problem, something is not working right: a somewhat dim lamp.
Step 1: you measure the potential over the battery terminals. Here it is 12,0 V. This is now your reference.
Write it down: V1 is 12,0 V. Then go to the right, which is step 2. You measure the potential over both sides of the part that does not perform 100%. In this example you measure a potential of 11,0 V. Write that down: V2 is: 11,0 V.
Hmm, one volt does not make it from Batt POS to Batt NEG, so to speak. We want all Volts to pass. Where can I look for that missing volt, in other words where is the resistance? For this we go to:
Step 3. Check if there's any potential over Battery POS and POS side of the lamp. Ideal outcome would be 0 (zero), indicating there's no resistance and all volts arrive. In our example 0,1 V is missing. This is acceptable. BTW, you can interpret that little square as things in between like a fuse and/or a switch.
Write down: V3 is: 0,1 V.
Now check the NEG side of the route: the potential over Batt Neg and the NEG side of the lamp. Also here the ideal outcome would be 0 (zero), indicating there's no resistance and all volts arrive.In this example we measure 0,9 V however. Write that also down: V4 is: 0,9 V.
Before we begin interpreting our results, let's first check we did the V4 measuring right.
You only have to remember one formula: V1= V2+V3+V4. Always.
So in our example: 12,0 = 11,0 + 0,1 + 0,9. Conclusion: we did it right. As already said, the 0,1 V missing in the POS route is not much of a problem. Possibly there is some minor resistance by a fuse and/or a switch. Not much to worry about. The 0,9 V in the NEG route is a reason for concern however. But at least we now know, where to look in order to locate it: the negative path. In our example, it's probably a rusty, dirty or loose connection. Could be the thick Batt NEG cable, connected to a recently powdercoated frame.
Ofcourse this is a simplistic representation. Depending on 'obstacles' like switches and/or fuses, we may need more steps to perform, but V1 must always be the sum of V2 and V--n. Also realise, I've limited myself here to describing a situation, where a component is not working a 100%. There's also the possibility, something is not working at all. I'd then start by isolating that part first and connect it directly to a known good battery to verify that part is OK.
-
Good explanation. I have always found the accuracy of readings to be problematic (fluctuations) with budget digital multi-meters...I'm not sure what make/model/meter that you use, or could recommend?
-
That’s really interesting info, thanks for posting as I know it will come in handy for fault finding in the future.
For this bike, which was probably an ex scrapper import from US, I am going to replace or repair all the dodgy looking electrical bits as it’s not a great deal of extra work while everything is stripped down. And I just know they will come back and bite me in the bum if I don’t 😣
-
Bryanj
I Have found HondaMan, I have read about him, I know he makes and sells things but have totally failed to find the site where he sell his things from or how to buy anything from him.
Do you have a link or the name of his site.
Thanks
-
Bryanj
I Have found HondaMan, I have read about him, I know he makes and sells things but have totally failed to find the site where he sell his things from or how to buy anything from him.
Do you have a link or the name of his site.
Thanks
Think this is it Murf https://sohc4shop.com/
-
Thats the one or just join the us forum and send him a pm
-
Personally I wouldn't bother and have the three fuses floating. I had to add two fuses: one for the horns and one for an auxilary wire. Just cut the wires and insert the fuses. The wires are short and stiff enough not to wander about.
-
You could also try Vehicle Wiring Products in the UK for a 4-way blade fuse box (Ref: FBB4T)
I used to supply them for RD250/400's a number of years ago.