I have Tax, Insurance and MOT for my Honda CM125 C, so I am now fully street legal as they say. Couldn’t wait to have a shakedown run and see if my labours over the winter months all worked.
Set off on a gentle run with a view to taking a trip to my mothers. A round trip of about 60 miles mostly on back roads. Everything seemed ok on the outward journey although I was struggling to see the idiot lights in the sunlight – if I had been thinking, that should have set the alarm bells ringing. Got to Mothers, did some gardening for her and then went to set off home again on my trusty steed.
Flat battery!? And these have no kick start. Managed to bump start it and get it running but very quickly realised the battery wasn’t charging and the lights where getting a little dim. I set off home fairly promptly and limped home by trying to use anything electrical as little as possible. Battery was pretty much dead by the time I got home.
More annoyed with myself for not checking the generator output than the bike but slung it in the garage and closed the door in disgust.
Got up next day feeling a bit better about everything and went out to the garage. Wheeled the bike into the sunshine and removed the seat and tank. Got one of my comfy camping chairs out and settled down with my multimeter.
The big one I was worried about was the stator wires broken or shorting to ground. The stator is now getting a bit difficulty to purchase and fixing would probably involve a company rewinding for me. I checked the three stator wires and all seemed good. Phew! I removed the regulator and the blocking diode and sat with the Haynes manual (have I mentioned how much I love those manuals) and worked through the tests. Blocking diode was blocking both ways – that’s not good. The regulator/rectifier (RR) was a bit inconclusive. Got some readings out of it but not all. Then I noticed a bit of corrosion on the wiring loom side of the six pin plug for the RR. Started taking a closer look and discovered the main charging lead was not actually attached in the plug. It had corroded through. That won’t work then.
So, to sum up I need a new blocking diode, replacement RR and a bit of re-wiring of the wiring loom connector plug.
I found a blocking diode with my old friends Wemoto. Bit shocked at the 16 quid price but couldn’t find it anywhere else cheaper so gave in and stumped up the cash.
Checked the Honda price for a RR and suffered a minor seizure. Two hundred quid! Tried my usual parts places and quickly realised there was a need for caution here. My RR has a part number of SH532-12 and there are quite a few units around that carry this number but have different numbers of wires and styles of connector. I have noted that some have five wires and some have six. Some have two, three pin connectors and some, like mine, have a single six pin connector. Resorted to eBay. The used ones on eBay looked pretty rubbish. Close inspection of the photos often showed what looked like damaged connectors and wires so decided it had to be new. The units with two connectors seem an awful lot cheaper than those with one connector. Decided to take a risk and purchase a unit with two connectors and six wires for the princely sum of 39 quid. Hope I am not going to regret this.
I carefully removed the plastic outer from the connector blades on my old RR. Similarly removed the outer casings from the blades on the new RR. Inserted the blades into my plastic casing with the wires in the right order. So far so good.
I then popped the outer casing off the wiring loom end and crimped a new connector on the end of the broken wire (found a good source for motorcycle connectors of every shape and size on eBay). Re-inserted the connectors into the casing so I now have a repaired wire and a new RR with six pin connector. While I had it all in bits I rubbed down the mounting bracket and repainted it as it was showing signs of rusting and added new stainless steel screws and nuts in place of the rusty steel ones.
Connected it all up and inserted my new blocking diode. Tank and seat back on and ready to test.
I checked the voltage across my rather depleted battery and it was showing as 11.55V with everything switched off. Connected up some jump leads off my car and started the bike. Removed the jump leads so the bike was on its own and then checked the battery volts at tick-over. I was reading 13.04V.
I have no rev counter so I was guessing on the speed but I dialed in what I though would be about 3000 rpm. The voltage crept up to 13.54 V. I gave a couple of serious blips of the throttle to see what the voltage peaked out it and it didn’t go above 13.80 V, which according to Mr Haynes is about right. Its supposed to limit everything to 14 volts. I let the bike run for a bit to put some charge in the battery and make sure it was going to last longer than two minutes. I repeated the tests with headlight on main beam and it had no measurable effect on the voltage. Based on these readings I have taken the view that this issue is fixed.
Blocking diode is now working correctly as I can’t start the bike without pulling in the clutch – just as it should have been.
I guess this is all part of running an older bike.