Can ignition timing go faulty during use?

[owain]

Well that was a short lived success 

The A10 went brilliantly for a short run around the countryside yesterday. Started well, ticked over nicely and pulled great. Until I took it to work this morning. The bike suddenly stopped working 1km into my journey. I went around a roundabout and engine just conked out. No life in it again.

I've just pushed the motorcycle home and back to square one. I took the spark plug out of the cylinder and kicked the bike over. Have a good spark. I sprayed engine starter into the engine incase it was bad fuel...nothing again. I cannot understand this motorcycle one bit. Cracking the engima code couldn't been this hard 

[RDfella]

Presumably the good spark was after it had cooled down? In which case almost certainly a duff condenser in the mag. Unfortunately that means a rewound armature as it's in the centre (daft design). Not sure about the lates ones that fit at the points. Look a bit small to me, but maybe worth a try.

[berger]

RD fella many years ago mine had similar problems, had the mag re-wound with what I think he said were 2 modern condensers and if one packed up the other took over but also at this time it started banging in the exhausts and  missing then picking up ,after the mag was done I found out  the points  were toast as well. glad I had the mag done though it was  a 1960ish mag and still had original wrapping. I put the platinum tipped points on and jobs a gooden. it seems when owains is getting hot is when the problem starts which at first I would say condenser, in my case I don't know weather mine was points- condenser- or both at the same time

[Swarfcut]

Hi Owain.  One more try.  Get yourself some plugs from a running engine. I re-read this thread and see you have new NGK plugs, which have (I understand) been the subject of counterfeit operations.  Maybe you got unlucky.

 Give the cylinders a good dose of fresh fuel down the plughole, then maggy end cover off, fuel off and get kicking with no choke, varying the throttle. It should fire and run for a couple of seconds. If successful, repeat with the fuel on and a bit of choke to keep it going.

 If it is still dead, time for another go at the magneto. This is still your number one suspect, reviewing this thread again from the start.

 If it will only run with continual priming down the plugholes, that suggests the carb is acting up. Try your old carb, cleaned and checked, the new one may be not as good as it could be. Check the fuel lines, just in case some sediment is being drawn down after your heroic test run.

 Once running OK cold, the classic symptoms of a failing condenser are  a reluctance to start when hot, and erratic running and sudden cutting out, again once hot. The condenser within the magneto is buried in the armature, at the drive end, where it is nice and warm.... they have a hard life.

 The Brightspark Magnetos Website will tell you all you need to know about why they fail and the simple effective options for a fix, essentially and very sensibly moving a modern type condenser to the points plate for easy access.

 If you go this route the existing armature does not need a rewind, just as long as it is electrically sound, and is used with a slight  circuit alteration to isolate the suspect condenser.  In the end the choice is yours, but for my money, conversion to an easily access  Brightspark condenser makes good sense if you are determined to retain a standard magneto.

 For a simple assessment of your magneto, I would recommend Priory Magnetos. Here bear in mind this is a small business, and opening hours and availability of service depend on existing workload, so best to make contact first by email via the website. If the armature turns out to be the problem, electronic ignition, typically Thorspark, is a good choice as it retains the defunct magneto  with ATD as a basic mounting and is fairly priced compared to a full house rebuild of your suspect magneto.


 Swarfy.

[RDfella]

Just to a add to my previous post - it's not unusual for condensers to be fine when cold but fail when they get warm. Trouble is new condensers will be of unknown quality and NOS are no better, because they can deteriorate with age. Wonderful.
Another thought - is Owain using suppressed plug caps? If so not only do they reduce the spark intensity, but they also cause a large rise in mag internal voltage - enough to make a mag fail. Have the test data on that somewhere and it's quite alarming.

[owain]

UPDATE:
I've just received the magneto back again from the repairman. Symptoms are still the same though. I get a shock if I hold the ends of the HT cables and kick it over but I'm not getting any indicator of combustion.

I'll change the fuel tomorrow and buy new spark plugs to see if that fixes the problem. Although I can't help but think that there still is another underlying issue causing the ignition to fail. It just seems very odd for the motorcycle to start running again only to die on me the moment I go around a roundabout.

[Swarfcut]

Owain
 Do the usual check of making sure the cylinder on compression has the pick up brush over the brass segment of the magneto slip ring, it's easy to swap the leads over by mistake.
 Does the magneto look as if anything has been done by your repairer? If it gives you shocks, back from being checked over I would expect it should give a bloody big spark in the open air. If this in order, another rough check of the timing may be worth doing.

  Leave the magneto cover off, it could be grounding somehow, through the kill button wiring.

  Give it a good dose of Start Yer Bas**d along with your new plugs. Just dropping the plug cap loosely onto the plug was an old trick to boost the spark enough to clear a fouled plug, as the spark jumped the gap between the plug and the cap as the engine vibrated. So try this, may be just the boost it needs to get it to fire up.

 Swarfy.

 

[duTch]

 

.....It just seems very odd for the motorcycle to start running again only to die on me the moment I go around a roundabout

 I don't recall that bit, but as suggested above, maybe there's something loose earthing it out, or maybe if there's a wire to a handlebar cutout rubbing or pinching when you turn 

[ironhead]

UPDATE:
I've just received the magneto back again from the repairman. Symptoms are still the same though. I get a shock if I hold the ends of the HT cables and kick it over but I'm not getting any indicator of combustion.

Sounds like leaky HT leads and or Plug caps. If all is good you should be able to touch the plug caps with the engine running & not get a boot . Or are you sticking your finger where the the plug is supposed to go

[owain]

Tried new NGK B6HS plugs today. No luck. I also tried a simple test: Spark plug tester connected to a plug cap with the other end grounded to the engine. When I get the the engine over the bulb lights up. When I introduce a new spark plug to the circuit and ground it to exactly the same point. The bulb does not light up and no spark can be seen.

I checked for a possible source of grounding but can't any and the above test seems to indicate that a unexpected ground isn't the issue. 

[RDfella]

Lets get back to basics here, or you'll be going round in circles. You say you get a shock from the ends of the HT leads. But that's no real indication. Need to hold the end of the HT lead about 8 - 10 mm away from bare metal and make sure you've got a fat blue spark. If no-one's around to help you to do that, open up the gap on an old spark plug and lay it on the cyl head and look for said blue spark.
Do you have a mag cutout on the bike - either on the mag or by wire to a kill button?
If no spark, have you tried it with the end cap off?
What condition are the mag pickups and HT cables?
Are HT cables wire core or carbon filament?

[owain]

@RDFella Thanks for the tips. I have mag cutout on it and I removed it when kicking the bike over but had no effect. I couldn't get a spark to jump 8-10mm either from the HT lead to the engine either.

I took the magneto off the bike to test it to see if it's a bad ground (although I was trying to ground it directly to the mag before anyway). Long story short, the little process on the rear of the contact breaker assembly (that little bit that sits in the groove in the spindle) has broken off. Now I have to get another contact breaker assembly before continuing with this horrific problem that has been plaguing me.

Oh also, I bought new copper core HT cables and new NGK non-resistor type plugs. The mag pick-ups were replaced by the repairman and seem to be a pair new replacements for the originals.

[chaterlea25]

Hi Owain
Surely the "repair man" should have looked and seen the contact breaker rotor problem??????
Is it a brass or steel points rotor?
A new "key" can be made and soldered into place Or
A competent repairer can press a new key 180 degree's opposite the missing one

 
John

[owain]

It's a brass one. I have a feeling that I may have broken it by over tightening the autoadvance bolt onto the mag spindle (maybe). I tried to solder a bit of flux myself but it doesn't want to bond to the brass (perhaps I'm using the wrong stuff). I also tried to 'build up' a little bit of material with my arc welder...in hindsite that was a foolish idea.

[groily]

The keys are fragile and if the cb unit has been shoved on out of alignment, the raised portion gets squashed when the centre screw is done up. Sometimes, it's missing altogether and there's just an open notch where the key used to be.
As Chaterlea says they can be reclaimed, or a new one formed exactly opposite - and they can also be repaired with solder if necessary. Fiddly job with swiss files etc after, but the brass will take it ok, and as the key shouldn't be doing any work beyond acting as a register, the thing ought to stay put, and survive.