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CarlB |
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CarlB L Plate Warrior
Joined: 20 Aug 2018 Karma :
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Posted: 20:13 - 20 Aug 2018 Post subject: Points problems, 1976 Honda CG 125 |
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Hi, new to the forum, just thought I'd post this in case it helps anyone else.
Gradual points creep on an old bike.
I bought a '76 cg125 a few weeks ago for a trip to France; it was mostly in good condition with a little bit of obvious work to do. The stator coil for the battery was shot so I had them both rewound, I fitted a new battery, I checked all the wiring and replaced connectors and sealed everything against water, I put a new back mudguard on to take the weight of a back rack as the old one was badly rusted and I cleaned and adjusted the back brake and replaced the front brake cable. The points were a shiny, newish replacement and worked fine. Remember that!
A few test runs and it all seemed good to go.
Once in France, in very hot weather, I found the bike beginning to falter.
First symptom: it died when coming to idle after a long run, I checked the plug, which was sooty, so then the air filter, fuel flow, dismantled the carb, nothing obviously wrong there so I suspected the timing. Off with the gear lever, side cover, checked the points gap- no gap. The retaining screw was still tight so that's odd. Adjusted the gap, let the bike cool down and rode on. Second time it happened, the next day, it faltered after a couple of hours riding and smoked a bit too, excess fuel smoke. Symptom of retarded timing, amongst other things. I wondered if the advance/retard springs were too old, maybe getting hot and weak and not pulling the rotating cam back to the low revs position properly; so off with the stator cover, the springs seemed fine, put a little oil on their pegs, adjusted the points gap again, let the bike cool and rode on. Over the next couple of weeks it became a daily routine to stop when the bike began to falter and smoke, take the cover off, adjust the points and ride on. I convinced myself that the heat and vibration was causing the points to creep very slightly and gradually retard the timing and the adjustment is so minute that it's really impossible to see any obvious difference in the screw position.
Ok, so today, still in France, it happened again but this time there was no more adjustment on the points. The slot on the backplate was at the max for advance so after today's adjustment there would be no more. Finally I realised that the cam follower must be rapidly wearing out, which was weird, until I inspected the cam closely and saw a little patch of pitting, old corrosion, which was acting as an abrasive, wearing down the soft cam follower pad.
Little hope of finding new points here in a day so I had to bodge. Chemical metal putty to rebuild the cam follower by a mil or so, and a tiny strip of brass foraged off my 6v testing screwdriver as a face to resist wear on the steel cam.
So far, it works. The bike runs ok. I've done a couple of short runs but I want the chemical metal to harden overnight before I stress it any more. The next long run will either be trouble free or I'll have bits of brass and resin flying off into my stator!
What I've learned so far: don't get fixed on a diagnosis, there might be another cause behind the problem that I haven't seen yet. |
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 21:46 - 20 Aug 2018 Post subject: |
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Interesting fix.
Oddly, I'm struggling to find a seperate points cam listed anywhere for an early CG125, even on the parts fiches. Is it actually a seperate part or is it part of the crank itself?
Is the felt pad stil in place and lightly oiled? ____________________ “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. |
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bikenut |
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bikenut World Chat Champion
Joined: 21 Nov 2011 Karma :
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steve the grease |
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steve the grease Crazy Courier
Joined: 26 Jan 2018 Karma :
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bikenut |
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bikenut World Chat Champion
Joined: 21 Nov 2011 Karma :
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CarlB |
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CarlB L Plate Warrior
Joined: 20 Aug 2018 Karma :
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Triton Thrasher |
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Triton Thrasher Could Be A Chat Bot
Joined: 16 Oct 2012 Karma :
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Old Thread Alert!
The last post was made 5 years, 203 days ago. Instead of replying here, would creating a new thread be more useful? |
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