Author Topic: Possible cause of my misfire  (Read 1657 times)

Online Minto

  • Resident Legend
  • *****
  • Join Date: Mar 2019
  • Posts: 518
  • Karma: 8
Possible cause of my misfire
« on: 06.04. 2019 21:20 »
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???
52 A10 plunger
Aprilia RSVR

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1630
  • Karma: 32
Re: Possible cause of my misfire
« Reply #1 on: 06.04. 2019 21:49 »
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.

Offline lawnmowerman

  • Resident Legend
  • *****
  • Join Date: Dec 2009
  • Posts: 624
  • Karma: 8
  • 1959 Super Rocket. Kent, England
Re: Possible cause of my misfire
« Reply #2 on: 06.04. 2019 23:02 »
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
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online Minto

  • Resident Legend
  • *****
  • Join Date: Mar 2019
  • Posts: 518
  • Karma: 8
Re: Possible cause of my misfire
« Reply #3 on: 07.04. 2019 10:16 »
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
52 A10 plunger
Aprilia RSVR

Offline Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Join Date: Feb 2009
  • Posts: 1652
  • Karma: 21
Re: Possible cause of my misfire
« Reply #4 on: 07.04. 2019 11:00 »
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. 

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1630
  • Karma: 32
Re: Possible cause of my misfire
« Reply #5 on: 07.04. 2019 11:14 »
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.

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4538
  • Karma: 41
Re: Possible cause of my misfire
« Reply #6 on: 07.04. 2019 11:51 »

 
Quote
..............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 *conf2*  *dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online berger

  • Wise & Enlightened
  • *
  • Join Date: Nov 2017
  • Posts: 1719
  • Karma: 12
  • keith.uk 500sscafe.norbsa project,honda 750fz
Re: Possible cause of my misfire
« Reply #7 on: 07.04. 2019 13:18 »
never put your finger where , that's enough of that. I use cotton buds soaked in meths no shocky *clap*

Online Minto

  • Resident Legend
  • *****
  • Join Date: Mar 2019
  • Posts: 518
  • Karma: 8
Re: Possible cause of my misfire
« Reply #8 on: 07.04. 2019 16:09 »
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
52 A10 plunger
Aprilia RSVR

Online Minto

  • Resident Legend
  • *****
  • Join Date: Mar 2019
  • Posts: 518
  • Karma: 8
Re: Possible cause of my misfire
« Reply #9 on: 07.04. 2019 16:16 »
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.
52 A10 plunger
Aprilia RSVR

Online RDfella

  • Wise & Enlightened
  • *
  • Join Date: Aug 2017
  • Posts: 1397
  • Karma: 12
Re: Possible cause of my misfire
« Reply #10 on: 07.04. 2019 18:10 »
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.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline bikerbob

  • Resident Legend
  • *****
  • Join Date: Feb 2011
  • Posts: 583
  • Karma: 8
Re: Possible cause of my misfire
« Reply #11 on: 07.04. 2019 18:40 »
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.
56 A7 s/a
63 A65

Offline lawnmowerman

  • Resident Legend
  • *****
  • Join Date: Dec 2009
  • Posts: 624
  • Karma: 8
  • 1959 Super Rocket. Kent, England
Re: Possible cause of my misfire
« Reply #12 on: 07.04. 2019 19:34 »
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
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 5588
  • Karma: 52
Re: Possible cause of my misfire
« Reply #13 on: 07.04. 2019 20:32 »
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.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Online Minto

  • Resident Legend
  • *****
  • Join Date: Mar 2019
  • Posts: 518
  • Karma: 8
Re: Possible cause of my misfire
« Reply #14 on: 09.04. 2019 01:20 »
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
52 A10 plunger
Aprilia RSVR