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It all started with an indicators fault on my Honda CM125CC. Stationary with no engine running they worked fine. Engine running at tick-over they worked fine. Riding down the road they didn’t unless I put my foot on the rear break pedal.

Its obvious, I thought, its an earth fault somewhere. So, I proceeded to clean and check every earth wire connection on the bike and after several hours of work made absolutely no difference to the issue.

In that case it must be the flasher relay. So I bought a new one, fitted it and that fixed it ……. not!

Out came my multimeter and I checked every voltage and resistance level mentioned in the Haynes manual. Nothing!

Having spent two weeks off and on working through troubleshooting the problem I could safely say I was no further forward.

My Dad always used to say if you can’t find the answer, you don’t understand the problem. So I put everything back together and did some further basic tests.

 Engine off and it worked fine. I started the engine and let it tick-over and it worked fine. I gently increased the engine revs and at around 3000 rpm the indicators stopped working. I dropped the revs a little and they started again. I increased the revs to 3K and they stopped. I put my foot on the break pedal and they started. Foot off the break pedal and they stopped. I turned the headlight on still with 3K dialled in and they started again. Still with me!

All this testing started to give me further clues and I dragged the multimeter out again and measured the voltage across the battery at different rev points and realised that the volts was going off the scale. The issue was the voltage regulator it wasn’t capping the charge voltage and when it got to 15V, the indicators stopped working. Switching on the headlight or anything else electrical would pull the voltage down enough to make it all work.

Bit miffed as its not long since I replaced the regulator. Anyway, bought a replacement and fitted it. It didn’t make a jot of difference. Still too many volts. Threw everything in the garage, slammed the garage door and went to bed.

A few days later I decided I was not going to be beaten by this and ventured back to the garage. Wheeled my trusty steed into the sunshine and got my folding camping chair out. Radio on, bucket of hot tea and I settled for a siege!

I ran various bits of wire out from connectors in the wiring loom so I could check stuff without having to take the bike to bits. This also meant I could check stuff with the engine running.  I wasn’t actually sure what I was looking for so the bike looked a bit like a shaggy dog with threads of wire everywhere with bits of coloured tape over the ends so nothing shorted out and I could tell which were supposed to be live and  which were supposed to be earth.

I then started measuring volts. Some of it was really basic stuff like volts across the battery. I then started getting a bit more technical as I started to think things through a bit – the tea was working.

I started to investigate more closely the volts at the regulator end of the black wire which is the sensing wire and drives the regulator. I realised this was seeing about a volt less than what I was actually measuring across the battery. My very simple mind was telling me that this could fool the regulator into thinking the battery was not charged when it actually was. I followed the trail of this wire through all the various connectors. I fairly quickly arrived in the headlight and discovered quite a bit of corrosion on the terminals of the big connector in the headlight. I cleaned the connectors thoroughly and then continued to the next block cleaning as I went.

I then reassembled the bike and checked voltages again. Much better. I was now reading exactly the same on the black as at the battery. Convinced I had solved the problem I then reassembled everything correctly and removed all my test leads.

Ignition on and check indicators. They work. Start engine and check indicators. They work. Rev engine to 3K and check indicators. They don’t work. Another cup of tea and a calm pill!

More in desperation I somewhat randomly removed the new flasher unit and put the old one back in. Ignition on and check indicators. They work. Start the engine and check indicators and they work. Dial in 3k and check indicators and they work!? Dial in lots and they still work. Foot on break pedal and they still work. Helmet on and a quick whiz round the block and they still work.

So, what was the problem. I can only apply a half arsed guess but I would say the corrosion in the wiring caused the voltage regulator to go a bit awol. The new flasher unit I put in may have been faulty to start with or could have been damaged by the over voltage from the regulator.  Anyways I now have a growing stock of voltage regulators in my parts bin and in future I will check for corrosion in the wiring before I do anything else.

I guess the moral of the story is, on a 30 year old bike always look for corrosion in the electrics first and only when thats been exhausted look for a component fault.

I guess this started with an issue with vibration. It got quite bad and I tried bar end weights on the handle bars and stuff to try and reduce the numb finger syndrome but nothing seemed to work. 

I have also been having an issue with the clutch. Its not smooth and at times its downright difficult to handle. Prior to taking it to bits my best guess was that I have some plates that are out of shape. I purchased some new friction plates and springs and, from Honda, some new steel plates.

Had planned to wait until my holiday to take it to bits but, well you know; cutting the grass or taking a clutch to bits? No competition really.

So out came the spanners. I had a real problem with one crank case bolt and I really thought it was going to shear off but lots of patience (very out of character that) and very gentle persuasion managed to get them all out without a break. Slackened off the four bolts holding the springs and realised I had a bit of an issue as things seemed a little wobbly.

Eventually got it all to bits and this was the problem.

As you can see, one of the spring carriers has broken off completely from the pressure plate. Its a classic crystalline failure. I had a roam around on eBay for a replacement and then decided if that’s happened to mine then perhaps I will opt for a new one and purchased a genuine Honda part from my old favourite Lings.

I also splashed out on a proper peg spanner to deal with the lock-nut. I made one to undo the nut based on the Haynes manual suggestion but decided it was going to be difficult to torque it up properly on reassembly so purchased a peg spanner from Wemoto which will fit a square drive socket wrench.

The actual clutch friction plates  and steel plates seemed in good condition but I replaced them with new anyway. I replaced the springs as well, just because I had some. I had a plan to clean the oil filter while I had it all in bits but for the life of me couldn’t get the oil pump screws undone so I have left that for latter when I have a new battery for my electric impact driver (can’t complain really I have had it 10 years and the battery just isn’t holding charge anymore). I reset the tappets and cam chain tension instead.

Reassembled everything and added my lovely new Athena gasket to seal the oil in and away we go. A very definite improvement on the clutch front and my vibration issue seems to have disappeared.

For the last few weeks since MOT time I have just been enjoying having the bike to ride and while doing that I have been addressing a few relatively minor issues along the way.

I have managed to clock up around 200 miles so far and early indications I am getting just over 80 MPG which is not bad as a starting point. The biggest problem I have had is that my lovely shiny new exhaust broke. The rear mounting bracket weld failed. As a temporary measure I have replaced it with the old exhaust which is keeping me going until I can get the broken bracket resolved.

I have a bit of vibration at the front above 50 mph which I am assuming for the moment is a wheel balance issue. I’ve done some basic checks and bearings etc. all seem fine.

The sprocket ratios are not working for me. I have now changed the front sprocket to the standard number of teeth. This suits my riding style and my weight much better but wouldn’t suit everyone. 50 mph in fifth gear is very relaxed and the engine is more than capable of maintaining that speed but if I need to accelerate I need to change down. For the roads I spend most of my time on going to work this is great as I can just poddle along at 50 and watch the fields go by. 60 mph is attainable if you rev higher in the lower gears before settling into top. I have maxed out at 68. These speeds are all indicated speeds and I would guess these are all on the high side of reality.

Getting the throttle and clutch adjustment right has proved a little challenging. I initially set according to the workshop manual but this proved quite uncomfortable in practice so for the clutch I have now set it according to where I want the bite point rather than what the book says. The bite point is now much closer to the grip than it would be if the clutch lever was setup according to the manual. This gives quite a bit more free play. For the throttle I have taken out a bit more of the cable slack then the manual suggests so the twist grip has almost no slack before things happen. I have found this much easier for me, particular in traffic.

I bought a host of minor bits to just fix bits missing or not in good shape.

I was a bit concerned about the battery terminals shorting out and causing a problem as the insulator on the positive had long since disappeared and the cover was missing from the starter solenoid. So I purchased these bits from Honda along with a battery cushion to make the battery a little more stable in the battery tray. I also purchased a complete new fuse and wire assembly which is the bit that links battery to bike electrics. This is the fused wire and on mine the fuse holder had broken and a previous owner had just soldered the two bits together with no fuse. I purchased a complete new bit including fuses to get that bit right. I also purchased the spare fuse holder just for completeness really.

I have purchased a new chain guide blade as the old one was very worn. Not yet fitted but will be soon.

A comment from the MOT station was that the washers which should be under the split pins on the foot pegs were missing. Not an MOT failure point but he suggested I get some washers and put them under as it reduced wear on the foot-peg parts. For the sake of a few 6 mm washers this is now done.

I’ve purchased a new oil filter/strainer but not yet fitted. I have a big piece of work coming up on the engine and I will do that at the same time.

I have on order some new pinch bolts that hold the top of the forks. Mine are 6mm bolts and I have discovered it should be 7 mm and these bolts are a special as not a preferred size so have ordered from Honda. I have also ordered a new air box seal as mine is missing and while I was in the parts bin I have ordered a front brake wear indicator.

I have a new clutch cable on its way as well to just hold as a spare.