The Question one needs to ask is . Have you got spark ? have you got fuel ?

The starter will engage and then throw out.
???

Maybe the battery is down a bit not enough grunt to do the job try jumping it

does it back fire at all ( timing out of wack )

These are the things you need to look at JudgeOZ
Good luck

Cheers Slider

Not firing or not winding over?

You say the starter engages then throws out?

Is that your way of saying the starter side of things is fine and its just not firing or is the starter only engaging for a moment and disengaging?

Toby

Try staring it a few times then pull a plug out and see if it has some fuel on it . if it has then good if not fuel is not going where it should be .

The next thing because the bike is getting old the wire,s are getting hard with age and in been so they draw a lot more current and so the starter is not getting what it needs to wind over correctly . also the wire,s to the points and all the ignition wire,s could be the same witch will compound the problem .

Also is there compression ?

these are just idea,s hopefully it will help

Cheeers Slider

JudgeOz,

I went through similar troubles to get my '79 on the road after years shelved in a garage. Can be difficult especially if you don't know its history and may have several system failing at once.

I'm still a bit confused by your last post. You say "the starter engages momentarily" This doesn't sound so good. Is it not cranking? .The starter should engage and stay engaged till you let go of that starter button. Is that whats happening or is it only engaging for a moment then disengaging?

You also say the battery is on a trickle charger but runs down quickly because of cranking. So it is cranking?

If its on a constant trickle charge and in good order you should get some good cranking out of it and you can move on to looking at spark and fuel as the next weakest link. But if its not strong and runs down after a few cranks, Id sort the starter side of things first.

A weak battery is going to wind the motor slowly, cause the solenoid to break its connection to the starter if the voltage drops too low, and result in a weak spark.

Toby

For old jigger like that you carn't beat Colt from HD Developments in Little Lonsdale st