Author Topic: Can ignition timing go faulty during use?  (Read 937 times)

Online orabanda

  • Resident Legend
  • *****
  • Posts: 900
  • Karma: 20
Re: Can ignition timing go faulty during use?
« Reply #15 on: 12.02. 2019 11:38 »
Are the teeth on the fibre gear stripped?
Been there, had that happen....
Remove the points cover and check that the points rotate when engine is turned over.

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Posts: 1353
  • Karma: 20
Re: Can ignition timing go faulty during use?
« Reply #16 on: 12.02. 2019 12:41 »
Quote from: Greybeard
Yes, you are correct. I was thinking of car distributors where the cam is inside the points heel.

In a car distributor, points gap closing up retards the timing.  Same as in a magneto.

Online Greybeard

  • Jack of all trades; master of none.
  • Wise & Enlightened
  • *
  • Posts: 4880
  • Karma: 27
Re: Can ignition timing go faulty during use?
« Reply #17 on: 12.02. 2019 12:45 »
Quote from: Greybeard
Yes, you are correct. I was thinking of car distributors where the cam is inside the points heel.

In a car distributor, points gap closing up retards the timing.  Same as in a magneto.

 *red* I think I'd better just shut-the-f*ck-up.

Offline owain

  • A's Best Friend
  • ***
  • Posts: 103
  • Karma: 2
Re: Can ignition timing go faulty during use?
« Reply #18 on: 12.02. 2019 22:11 »
Thanks for the quick replies. The bike hasn't wet sumped (I have a plumbing valve to completely cut off the oil flow when I'm not using it). I'll check the pick-ups first seeing as that's the simplest and will have a look at when the points separate with a marked paintbrush through the spark plug hole. I haven't taken the mag off the bike yet Dutch. I was a bit fed up with the bike when I lasted posted and have been putting my efforts into rebuilding my A75 engine during the winter. Mag removal and sending it off to get tested is gonna be my last resort right now.

When plugs are removed, I can see a bright blue spark with a reasonably mild kick...but it doesn't spark every time. Out of 10 kick attempts, I'll get a spark 7 times-ish.
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline owain

  • A's Best Friend
  • ***
  • Posts: 103
  • Karma: 2
Re: Can ignition timing go faulty during use?
« Reply #19 on: 13.02. 2019 18:04 »
An update on the problematic A10. I checked the magneto plugs and they appeared clean. Timing was very slightly off, so I reset it again to 11/32" BTDC in full advance. I'm happy with the timing there but when I kicked it over there was just a very brief combustion but died immediately. No signs of life since. I cleaned the points on the magneto again and tried kicking it over. No luck. I switched the high tension cables over. Still nothing.

I even ran down the road and dropped the bike into 2nd gear a few times but not a single sign of combustion.

Here's the strange part...after running down the road with it, I got out the spark plug tester and plugged in between the high tension cable cable and the spark plug. I kicked the bike over. No light to indicate a spark. I then detached the spark plug and just earthed the spark plug tester to the chaincase. Big bright light came on with every kick. Indicating that there is an electrical input. So I tried plugging a spark plug back onto the end of the spark plug tester (ensuring a very good connection) and earthed the spark plug on the chaincase...No light, albeit a very dim light and no visible spark.

Scratching my head as to what is going wrong. There is an electrical input reaching the spark but no spark is forming :/
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Posts: 1353
  • Karma: 20
Re: Can ignition timing go faulty during use?
« Reply #20 on: 13.02. 2019 18:43 »
Does a new plug spark?

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Posts: 7578
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Can ignition timing go faulty during use?
« Reply #21 on: 13.02. 2019 19:09 »
G'day Owain.
Do you have resisted or non-resisted plug caps?
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline owain

  • A's Best Friend
  • ***
  • Posts: 103
  • Karma: 2
Re: Can ignition timing go faulty during use?
« Reply #22 on: 13.02. 2019 19:50 »
Brand new spark plugs but no spark. I'm running NGK B6HS spark plugs. So there shouldn't be a resistor in them and this spark plug type has worked relatively well for me to this point. I've also checked the spark plug gap (0.018"-0.020").

I'm totally baffled though. Spark plug tester is showing a bright light with a gentle kick when it is grounded to the chaincase but as soon as I add a spark plug and ground that to the chaincase. No light or spark.
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline Swarfcut

  • Valued Contributor
  • ****
  • Posts: 378
  • Karma: 8
Re: Can ignition timing go faulty during use?
« Reply #23 on: 13.02. 2019 21:25 »
High Tension Electricity is funny stuff and can defy all logic. Test the plugs by substitution with known good ones. Further  checks before you condemn the magneto are to remove and inspect the carbon brush between the magneto body and armature, located under the brass slot headed screw adjacent to the nameplate. No electrical path here means the HT current cannot return to the armature to complete the HT circuit. With no load the HT current can usually find a way back, but is unable to do this when there is a load in the circuit... as I said it was funny stuff.

    A brass contact breaker carrier usually also has a carbon brush under it to earth the points to the body, the later steel points carrier is a slightly different electrical set up and does not have this brush. An inherent flaw with these penny pinching universal rotation steel points is that if the steel spring blade touches the cam ring, the LT circuit bypasses the points and the result is no sparks or erratic running.

 If these are in order I would suspect condenser failure.

 Swarfy.

Online Bsareg

  • A's Best Friend
  • ***
  • Posts: 199
  • Karma: 2
Re: Can ignition timing go faulty during use?
« Reply #24 on: 14.02. 2019 09:17 »
On the subject of brushes, you may have a set of those crappy lucas pickup brushes fitted . They would throw carbon over the slip rings causing leakage to earth. Might be worth a rag in the pickup hole to give the slip ring a wipe. If tgat works buy some brushes from Brightspark.
C11,B40,B44 Victor,A10,RGS,M21,Rocket3,REBSA

Online Rex

  • Valued Contributor
  • ****
  • Posts: 380
  • Karma: 0
Re: Can ignition timing go faulty during use?
« Reply #25 on: 14.02. 2019 09:48 »
Lucas copy maybe, but not genuine Lucas. Right what you say though...I've had carbon smeared around the slip ring through that duff batch of brushes some years back.

Online bsa-bill

  • Wise & Enlightened
  • *
  • Posts: 5201
  • Karma: 59
Re: Can ignition timing go faulty during use?
« Reply #26 on: 14.02. 2019 10:02 »
Had this problem a few years back, cured it the quick way (fitted Pazon), however if earth is a suspect remember the maggie has an earth brush at the timing case end, I did not check mine at the time (confessional ) so might be worth a punt
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline Swarfcut

  • Valued Contributor
  • ****
  • Posts: 378
  • Karma: 8
Re: Can ignition timing go faulty during use?
« Reply #27 on: 14.02. 2019 10:16 »
    I got to feeling this thread is getting familiar, so I have just read all of Owain's posts.  Cheered me up as it looks as if the curse of the A10 is currently residing in North Wales, and a long way from me.

    This bike has had a lot of time and effort spent, but seems to be mostly an unreliable runner, with one or two episodes of really showing what it can do.

  I reckon if there is an award for perseverance in the face of adversity,  Owain would win by a landslide. Makes another forum member's oil feed problems look like a walk in the park.

  Like all reluctant motors, it can only be  electrical, carby, or mechanical.  Time to stand back and consider what's what, and make sure these three elements are set up correctly.  My thought is that the magneto, despite a rebuild, is the weak link. Providing the charging circuit is reliable, a Thorspark system is a cost effective and reliable solution, allowing the magneto body and armature to be retained but with the benefit of electronic switching and no permanent alteration to the magneto. It also times the sparks in both cylinders exactly the same.  Compared to another overhaul or a new magneto  I know where I would be inclined to punt my cash.

    Spring is in the air and the open road beckons......you need this fixing soon.

  Keep on spannering,  Owain


 Swarfy.
 

Online RDfella

  • Valued Contributor
  • ****
  • Posts: 281
  • Karma: 4
Re: Can ignition timing go faulty during use?
« Reply #28 on: 14.02. 2019 11:23 »
Swarfy's comment 'Makes another forum member's oil feed problems look like a walk in the park' presumably refers to me. I'd happily swap the ignition problem for mine. In my case the lack of oil flow is merely the latest in a long line of irritating faults. Sort of the straw that broke the camel's back.
Ref Musky's post - the danger of using resistor plug caps with magnetos is widely underestimated. I once posted the details of testing which proves resistor caps put a massive load on the mag, sufficient in fact to cause the windings to fail.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online groily

  • Wise & Enlightened
  • *
  • Posts: 1011
  • Karma: 17
    • www.brightsparkmagnetos.com
Re: Can ignition timing go faulty during use?
« Reply #29 on: 14.02. 2019 14:04 »
A few thoughts for what they're not worth, if it's indeed a mag thing.

First - have you got close to 0 ohms from inside plug caps to carbon brushes on pick-ups? With the brush, spring etc there'll often be a small resistance, few ohms maybe. But if loads of ohms show up, or 'open line', then the plug cap isn't attached correctly.

Secondly, small variation in points gap isn't the problem here I don't reckon. It affects things slightly, but as long as the gaps are somewhere close to correct and the points are squeaky clean, it should work. A good wheeze is to take an old plug, grind off the earth electrode, and stick that on the HT lead. With a good 4mm-ish gap, you should get a smart crack of a spark at kickstart speed, no problem.

Third, Swarfy's point about steel cb assemblies - the blade must not kiss the camring or it's bye-bye some or all sparks.

Fourth, a quick HT test  . . . if you put a meter on the Resistance scale from the brass of the slipring with a pick-up off, and the other probe to mag body or a good earth, what do you see? Should be c 5000 ohms typically on a K2F. Open Line says a break in the winding, or that slipring-to-coil contact is absent. There should be no problem in this department  . . . but you never know.

Fifth, ref possibility of timing having altered  . . . If the ATD assembly hasn't moved and the teeth haven't stripped, what does the keyway on the cb backplate's male taper look like? Does it still exist and does it engage properly with the female tapered bore on the armature? If the cb is not correctly positioned, the thing will work badly, or not at all, as the internal timing will have been lost. The keys are fragile and can be wrecked by clumsy fitting of the assembly, also as a factor of age and loads of 'on-and-off'. Hard to feel with the mag on the bike if the drive is connected, but with it off the machine (or with just the ATD off so you can feel what is happening), can you see that the points start to open just after the flip points of the armature (which you should be able to feel easily)? (The key can be reclaimed using a little broach made out of, say, a bit of blade from a small reamer, if need be.)

Sixth, it's a tough one to test, but I wouldn't be totally surprised if the condenser(s) that will be in there have failed, even though the problem isn't the typical 'just when hot'. The hassle here is that you can't test the thing while it's wired to the primary winding, and it's made worse by the fact it will be potted in resin and bloody hard to get at. But if all else tests good and it's not a fuel / valve / other problem, that's maybe where you'll have to go next, unless you want to go electronic of course.
Bill