still not starting

[Barnsey]

Thanks for that lengthy discussion Steve. I will be working through that, I won't give an even longer answer right now. Having refitted the points I will double check the timing. I take onboard your point about winding the engine FORWARDS to the 7mm point to take up the slack in the system.
I will also check the distance that the spark is capable of jumping.

I held the timing cam in the advance position with a screwdriver.

I am checking the points opening and closing with the multimeter.  And I did check the spark with a neon tester, although it is easier to check the spark with the plug out. 

[Aquarius]

However, out of curiosity, is there an electronic ignition which will work on a 1963 C15 with 6V? 

  Ian

Is this any good to you? Says 6 or 12volt. I run a 12v electronic ignition on my A10.  https://www.classicmotorcyclespares.com/index.php/default/electronic-ignition-self-generating-bsa-c15-b25-b44-b50-with-lighting.html

If you want to go down this route, the kit listed above (out of stock!) is the Electrexworld kit, see here
STK-100D-DC

[rhyatt]

Do you have the distributor ignition or the side points.
Reason I ask, the books I sent you were very clear,
Distributor timing was set retarded and sidepoints ignition set fully advanced.
What do you have ?

[Barnsey]

Well, with only one cylinder it isn't technically a distributor but I would say it is the distributor version, as it has the points in a mushroom at the side of the engine. 

I wasted hours of time this afternoon trying to set it up by both methods,  advanced at 7.1 mm and retarded at 1.6mm (1/16")  In practise setting it up retarded is a lot easier as it is a fiddly to advance the mechanism by hand. 

  However, after several attempts achieving nothing I found an issue in that the new condenser is almost 3mm longer than the original.  This small difference pushed the contact spring out so that it wasn't following the cam through its whole cycle! 

  I can't believe how new parts are so often rubbish straight from the box, and a Lucas part too (red box).

  Can anyone recommend a known good condenser? 

  Running out of time again for today, and it is hot in my cabin!

[Steve.S]

I think you'll find it's pronounced 'Rucas'.

[iansoady]

Modern Lucas shares only the name with the Birmingham original.

[rhyatt]

If it's a metal mushroom behind the cylinder barrel , then that's refered to as a distributor.
So follow the instructions , from memory 1/16" before tdc in the retarded position , don't touch bobweights.

Have you determined the 1/4" spark gap colour , blue or ?

[Barnsey]

I put the original condenser back in and tried again with the piston at around 2mm BTDC and retarded .  Once again the dizzy is around 90deg out from where it started.  This is bonkers.  The terminal for the wire is now on the side of the bike which just seems plain wrong.

So I checked the manual and it said to check that the valves are both closed, and it is on the power stroke, which it was. 

Getting weirder.  Surely if the dizzy rotates once in four strokes, then 90deg would be one entire stroke out!  That would put it at BDC. 

I haven't got as far as checking the spark yet. 

[V500]

The capacitor doesn't need to be inside the distributor/mushroom anyway. Works equally as well attached to the outside of the body.

[Barnsey]

I didn't manage to get a spark between the lead and a vane, as previously described, but I tried opening a spark plug up to 3mm and it sparked across that gap, so it seems to me that the spark must be reasonably strong. 

[rhyatt]

What colour was the spark , strong blue crack

[scifi]

If you have a centre punch or small cold-chisel, you can put two marks at the junction of the distributer and crankcase.  This will be a reference point for further experiments.   I did the same with one bike, and found it ran best when the marks were just misaligned by about 1/16 inch.   But at least I knew where to reset it.

[Barnsey]

I would have said that the spark was pretty thin, and white, although it was hard to tell when it was only there for a split second.  Checking the colour of sparks is obviously a skill I need to learn.

The new timing position is so completely different to where it was that I didn't believe it was right until I had done it several times.  If anyone can tell me how it was possible for it to run at all I will be glad to hear.  I thought seriously about kicking it over, to see what happens, But I could do without any disasters at the end of a Sunday, so I postponed that to next weekend. 

  For the moment I am marking my positions with a permanent marker, as I can clean that off with spirit, but, when I am happy I might use a dot punch as suggested. 

   To be continued......

[rhyatt]

Ok thin spark.
This could well be the issue all along.
If it is a weak spark outside the engine , even the meagre compression ratio of the C15 could well extinguish this spark when inside the engine .
Basically , blow it out and it won't run.

Was this test using just the ht lead against the engine or a spark plug pushed into the plug cap

[Steve.S]

3mm in English is less than 1/8" and will be quite useless, although when you get your spark gap tester, I imagine it will jump more than that. If you find it jumps 5/16", then you can forget about the strength of the spark and move on.
By 'vane' I assume you mean 'fin', but it's no good trying to hold the HT lead with your hand. You need to fix the HT lead so there is a gap of 1/4" and then 5/16" between it and the fin or vane, maybe with a bit of wire.
From what you have said, I get the impression you're not setting the timing correctly. Now it is all assembled, just connect your multimeter, turn the engine over in the correct direction of rotation on the compression stroke until the meter reads zero, and measure the piston distance. If it's 1/16" from TDC, your ignition timing is correct, and you can move on to the next thing.