Possible cause of my misfire

[Minto]

Evenin' all
Just done yet another oil change on the A10 and took it around the block a few times, while I was out it was misfiring quite badly to the point that it felt like it was only running on one cylinder at times. I limped it home and tried pulling each of the plug leads off to see if I could determine which side was missing, assuming it was the left (I'd had an issue with the left side recently) pulled that first, obviously now only running on one. Plugged it back on, still mis firing so as I reached for the right hand plug lead, as soon as I touched it I got a massive belt off it, jarred both my thumbs, (the other hand was on the handle bars.)
Can I safely assume that I need new plug leads???

[Swarfcut]

Yes and no. It runs on one, so the LT side of the maggy is OK. The fault is between the slip ring and the cylinder head. So, plug, plug cap, lead, pick up body, pick up brush. All in the chain are suspect. Take out the left pick up, see if the carbon brush is in place. Then swap the good right side lead for the left one. If the right side still works OK, left the same, then it is down to the left side pick up and/or carbon brush, the plug or a mechanical fault.

 Swarfy.

[lawnmowerman]

What Swarfy said but also check for carbon on the slip ring. Some dodgy soft brushes and holders on the market. I cleaned the slip ring and changed the brushes and holders for quality ones from Brightspark and it was like a different bike. (You may need to change the acorn nuts too because the threads may be different).

Jim

[Minto]

Cheers folks, I was convinced that having received a massive belt from the plug cap, it was arcing from that. Always good to have a list to go through though. Will report back when I've fixed it or broke it more.
Cheers
Jase

[Triton Thrasher]

You can get another shock from the slip ring, if you turn the engine over, with your finger pressing a petrol-soaked rag onto the ring. 

[Swarfcut]

Minto... Additional thought. Check the points gap on each cam lobe, the cam ring may be worn unevenly, or alternatively the points plate itself may have a bit of wobble and the mis fire on the bad side is simply due to the points not opening enough to fire regularly. Opening the gap may be a quick cure, but be prepared for rougher running. Observe the magneto  running with the cover off, any wobble will be seen in the centre bolt.

 Clean the slip ring with a paper towel or rag, rotate the armature bit by bit, but don't put your finger down the hole and spin the maggy. You know the HT side is OK from your earlier test! Like the Thrasher says.

 Swarfy.

[duTch]

 

..............Observe the magneto  running with the cover off, any wobble will be seen in the centre bolt. .........

  I would think if that's the case would be due to a worn bearing or some other calamity....my gaps were different due to the cam being a sloppy fit in the housing, rectified by packing one side..... the bolt should be snug in it's taper and unable to move laterally  

[berger]

never put your finger where , that's enough of that. I use cotton buds soaked in meths no shocky

[Minto]

Well, had a look this morning, the plug cap on the R cylinder was split where the lead joins it and Not actually screwed into the lead. Haven’t got any new ones in stock in the only shop open around here so codged that one back on and reinsulated around where it had split with insu tape.
Still running really badly, misfiring, puffing out the carb,  backfiring, so had a look at the points, the gap seems a little tight both lobes the same(ish). Ran out of time to do much today but new leads are definitely going on and new plugs, and I’ll try a bit more gap in the points (where can I buy some more gap, or will any type of gap be ok, I’ve got loads of knowledge gap, and a big funding gap, is that suitable).
Where the ends of my leads enter the pick up body, the ends have a big blob of solder on them, is this normal? If not what’s the usual method for ensuring good contact with the pick up?
If I want to remove the pick up to examine it, do I just turn the retaining clip to and pull the pick up body out of the mag to remove it? Or will something bad happen if I do that?
As you wil have gathered I’m very new to A10s and magneto ignition, in fact to pretty much everything.
Thanks very much again everybody, brilliant forum 👍
Jase

[Minto]

I also tried swapping the plugs over, and the leads, but it seems to be running rough and missing intermittently on both cylinders whatever I try.

[RDfella]

If you're getting a belt off the plug cap it's nothing to do with magneto or anything else - solely the cap or, less likely, the HT lead. Cause of the misfire could be anything that's been suggested, but the fact you got a shock sounds suspiciously like you've found the problem. And make sure any new cap is not the resistor type - they destroy magnetos.

[bikerbob]

I really think you need to invest in new plug leads and HT lead as for how the lead fits in the pickup you bare the end of the lead and fit a split copper or brass washer over the lead and splay  the end over the washer then fit.

[lawnmowerman]

I really think you need to invest in new plug leads and HT lead as for how the lead fits in the pickup you bare the end of the lead and fit a split copper or brass washer over the lead and splay  the end over the washer then fit.

I also like to run some solder over the washer to hold the splayed ends securely. Probably does not make a lot of difference but it is something I have always done.

Jim

[RichardL]

I really think you need to invest in new plug leads and HT lead as for how the lead fits in the pickup you bare the end of the lead and fit a split copper or brass washer over the lead and splay  the end over the washer then fit.

I also like to run some solder over the washer to hold the splayed ends securely. Probably does not make a lot of difference but it is something I have always done.

Jim

Jim,

I think it does make s difference, but not a good one. The point where the bare copper enters the solder becomes a small-radius bend point that can lead to strands breaking. Not a problem in static (that is, non-moving) electrical and electronic connections, but should be considered when there is flexing and vibration.

Richard L.

[Minto]

Made some new leads and put some new plugs in today, less misfiring and back firing but still feels a bit rough, could be my imagination though.
However, I’ve now found a head gasket leak. Great!
Cheers people
Jase