classic motorcycle forum

I almost feel the Same!
The capacitor is the original. Easy to disconnect and see what happens.
I'll try anything.
I have a new substitute which needs a different mounting tab to use.
Neworiginalones Ive never found.

If it was broken, what effect would that have in the short term?
It stops erosion of the point's contacts and not much else?

Thank you as ever for the interest and suggestions about this 'issue'.

The bike with a strong 12V car battery, a good 12v coil, a new HT lead (but this was a length of heavy duty wire, not real HT lead), all other leads were new automotive loom wire, all connections were soldered, not crimped.
As I said at the time, when I connected the ground wire there was a light sparking with the points open or closed at the -ve battery terminal.
The condenser was the original one.

I turned the engine flywheel by hand until the plug sparked. The spark 'intensity' was much the same as the spark from the 6v magneto.
The timing marks on the static and flywheel parts were in line, the engine was 5mm Before TDC, points @ 0.4mm

The spec for the engine is 5mm btdc, a figure found in various Terrot handbook pages. Most 2 strokes are 2mm btdc?
Away from this set-up I have tried 10mm btdc, 5mm, 2mm and TDC.

In all cases when the engine has run it has been @ 5mm btdc.

OK, with the 12v system attached I tried to start the engine with the large Chinese carb (used because the engine last ran with it) and some mighty hard kicks, about 20. Nothing happened.
Out with the (wet) plug, clean with brake cleaner, rub the electrodes with fine W&D, tea spoon of 30:1 in the hole, fit plug pdq and kick hard, 20+ times, nothing, not a glimmer of a fire-up.

Next day, remove the 12 volt kit, remove plug, clean etc and after some hard kicking it fired and ran. I stopped the engine by closing the throttle, and after 10 seconds tried to re-start it. Nothing at all.
So, the 12V test showed the timing to be right, the plug sparking outside the engine, no combustion.
The only times this bike has run has been on the original magneto.

I have very limited 2 stroke experience, and what I have is around Lambrettas.

The engine is all original, the bore is really good, piston is standard size and a nice fit, rings are new. When I stripped the engine the rings were solid in the piston due to carbon.
There was a lot of carbon build up in the lower crank case which must be evidence of blow by.
I know I can get a new piston, I think about 0.5 and 1mm over size are available, so if I have to I can have it rebored to suit a new piston, cost would be about £150

My back ground is in mechanical engineering, new products, 5 year classic indentured apprentice, and I did my first Lambretta when I was 15.
I have built several cars, restored 6 and have raced  cars for 27 years.
I have a full bike licence, but after doing 3 hours riding on a modern 175cc bike 2 years ago I realise I don't want to ride these things due to the current breed of car drivers around here...

Thus I restore bikes for winter fun and sell them, not to make a profit, but to make room for the next one!

Below is what I normally work on, and proves I know enough to be dangerous! 



And my last 2 restorations:

But did you check that you had a good spark?

I posted a while back that I thought the basic problem was a degraded flywheel magneto and suggested (as others did also) that you rigged up coil and points. I don't know why it didn't work/you didn't persevere with that set-up?

Because that's how I feel as above!
Not really ready to spend ££££ with a specialist to go over the same ground, but I expect he knows a lot more than me (obviously).
Got to find a new angle on this thing.
Just do not know which way to turn, so trying to go back to basics, compression, fuel, sparks.