Guys,

I’ve mangaged get the beast back on the road but it kept cutting out when warm. This is ignition related not fueling etc as when it cools down it fires back up and off we go again.

Now, new coil, HT cap and lead and plug.

Checked the points and they’re burnt to buggery.

So I’m about to replace the condenser but then noticed the black wire from the condenser which passes out into a diode or something before connecting to the loom was totally caked in crud.

Could this wire be my trouble? I can’t seem to find its purpose.

Help!

The diode prevents to engine from starting/running backwards.. It can be bypassed or DEET might have a new one.

I still have some of the diodes for these.

Thanks but my bike starts and runs fine until warm.

Not sure the diode is the issue and from.the responses I'm assuming it's not and the condenser is my issue.

If this black wire has a poor connection does this cause the condenser to act up? I'm thinking not.

I would try replacing the condenser. Should be cheap and as mark said nix the diode or replace. Condensers do go out and my experience is that they limit top revs first because they need more capacity to sustain high revs, then they get worse down the rev range til nothing. Heat makes all electronics work harder and exacerbates any known problem. If anything you will have a spare for your kit if not the problem.

Points do get black & cruddy over time but surprising what still works. Keep the source coil in mind. If it was CDI i'd be looking at the source coil. Points source are heavier windings but can still give up after--40 years. Not sure how i'd test it running but an ac volt meter on the black up to the loom & watch it intently until it cuts out. If you have enough revs on you might see the needle drop to zero immediately while motor's still spinning down. I'd think condenser would run erratic for a bit before stopping & not just cut straight out--depending on revs of course. Crook condenser you can often see the points arc hugely compared to a small spark in the dark. Talking using an analogue AC volt meter.

Thanks for this.
I replaced the condenser and it seemed fine, rode it around for about 30mins.
Then I killed it, it wouldb't start hot.
Pulled the plug, let it cool and started again.
Then stopped, let it cool, started and the ignition cut out again about 100m up the road.

Pulled the tank off to check the coil etc and noticed that the black and white wire connected to the coil was very loose. could this cause these symptoms?

Sorry to say--i still vote the source coil, but been wrong before. Plug cap resistor is a thought--but likely would not run at all. Close the plug gap to ridiculously close to see if it helps a possible source coil weakness or shorting together of the windings from heat & vibration. Suppose hat doesn't really explain why it comes right on cooling--but!!--that's what they can do talking fine winding cdi type coil. Also make sure the source coil isn't the type earthed through the lighting coil like early dt1 250's whereby if the lighting coil is faulty then it'll bugger up the source coil running. Maybe close the points down too--to maybe 10 thou. I know it'll retard the timing but only experimenting chasing the source coil possibility.

If the diode is shorting it could be heating up and this could suck the juice from the ignition system. Could you also measure the voltage at the ignition coil wire when cold and when warm before it cuts out.

I'm attempting a long run tomorrow and I'll see how she behaves.

I see what you mean regarding the source coil. That's what a friend also mentioned.

Wouldn't mind but I'm expecting to ride 2000km.this week on it.....