Lucas K2F Magneto No Spark

[Terryb]

Hi All,

I have a sick Shooter, after a 150 mike ride yesterday the bike started to miss fire at low rev's and then eventually stalled. Managed to get it home, but now there is no spark. Before this run, it was running sweet as a nut, first kick starter.

Have had a look at the end cap on the Mag, the only thing that looks doggy is the length of the carbon contact which makes with the centre screw. This is worn down to the brass retainer. Could this be the problem?

[muskrat]

G'day Terry.
The bike should run without the end cover on (if the camring stays put), it won't turn off. But the dust from it may have fouled something, earthing a bit that's not meant to be. Give the points area a spray with electric contact cleaner and a blast of compressed air and try again. Note if the bridge in the end cap doesn't make contact with the center screw your kill switch won't work.
Cheers

[victortrry]

I had the same problem on my 1954 GF been out for a ride then started to misfire, what had happened was the cam ring had turned and the blade spring on the points were touching . the problem was the rivet that holds the cam ring in its position had come out a little and allowed the cam ring to turn.
Pull the rivet out and inside you will find a piece of shaped steel, turn it around so it fits the cutout in the cam ring then knock the rivet back in. If it does it again put a bit of shim in then knock the rivet in.

Victor

[Triton Thrasher]

Always do the obvious first.

Are the plugs clean and gapped?

Are the points clean and gapped?

Do the points open and shut as they rotate?

[Terryb]

Had an email from a gent, which I've lost, regarding the end cap and possibility of the carbon shorting out on the brass. Surely, the carbon and brass are conductors, therefore they are connected. I thimk its more blikely that the carbon is so worn down, that its not making contact with the points centre screw.

[bsa-bill]

the carbon is so worn down, that its not making contact with the points centre screw.

that would stop it stopping, would not stop it running, the carbon brush runs against the central screw and is wired (or should be) to a switch (push button) to earth, when pushed the switch completes a circuit from the central screw to earth thereby killing the spark, so maybe check the pushbutton and as has been said anything in the points that shorts them to earth

your right about the brass/carbon

would check as Triton Thrasher suggests, eliminate

[wilko]

If they're steel points this can happen.

[Terryb]

Hi All,

Checked all of the obvious things. Cleaned slip ring, points adjusted, plugs re-set and still no spark. Looks like its going in for a re-con. Strange thing is that its only done 2K since the last one. Thanks for the advice.

[bsa-bill]

Well there are refurbs and refurbs I guess, while the mechanics of the thing don't change the quality of parts used is out of your hands once the postie takes it away, I  had both mine done at the same place based  on the fact that the first one goes fine on my Flash so sent the second one to same place.
However it refused to start my Rocket type so swapped them , result both work fine on my Flash  but neither of the two will start the Rocket (higher compression) .

Lesson learnt but disappointing, when time and cash allow I'll send it to one of the guys here for a check over and fix, suggest you ask for a private quote from the guys here they both (might be more than two) seem genuine blokes

[duTch]

 Hiya Terry- I had a similar thing happen a couple of months ago, did all he obvious clean-ups and checks, but really nothing- had a couple of tongue lubes and ran out of daylight.
 Next day it fired up like nothing happened...

 Have you done a finger on the slip-ring/plug leads..?
Change plugs?

[bsa-bill]

Change plugs?

good one Dutch, probably the most obvious but missed by all so far unless Terry has tried a new pair.
 quite a few here (me too) have experienced plugs go on strike  - blaming Modern fuel and unvarnished inner porcelain bits in the plug for them shorting out so no spark,(wet soot = carbon = conductor = short) just an opinion held by many , may be right or maybe something else but a new plug generally solves it

[Triton Thrasher]

Change plugs?

.....probably the most obvious but missed by all so far....

Oh, he'll have tried new plugs before asking on the internet!

[Terryb]

Hi Guy's,

Problem solved. Not easy to see, but the contact centre screw had come undone, enough so that at speed the points assembly was stable, but when the rev's dropped the spring was shorting out. Hence no spark on kick over.

Gave the whole assembly a good clean, checked all the insulation. Re-fitted them and checked the gap and it all works fine. Just need to renew the end cap some time. Anyway thank you all for your help and suggestions.

Terryb

[Triton Thrasher]

Interesting that you say it was recently overhauled.

Mag specialists aren't the best at tightening screws, in my experience.

The centre screw is part of the LT circuit. If it's loose, you'll have problems even if the points stay in place.

[Terryb]

I think I'm tending to agree with you TT about this Mag specialist, but in his defence, the recon was done in 2008.

However, the bike has stood around for the last 6 years and 600 miles of the 2K has been done by me in the last 3 months. Never the less the centre screw should not have come loose enough to stop the bike.

Did a 25 mile run yesterday and she ran OK