ETZ 125 electrics?

[tomx]

My dear old ETZ 125 (see 125 section), has been giving me a right pain.

Got it all up and running but it had a terrible misfire. Just to be safe I replaced the points, the condensors, the coil, the plug and then the carb.

There was a spark, but it would not run. At all.

In checking the timing I noticed the voltage was under 10V, even after charging the battery. Out of desperation I attached a 12V booster and it ran perfectly. As soon as I took the booster off it died. This all sounds like a short in the system somewhere. Could it be the coil doesn't have a good earth?

Yesterday I charged the battery, and after trying all the electrics, it was still showing 12.6V, which I'm pretty sure means it's good. Why then am I only getting 10V with the points open? It still only runs with the booster fitted. Guess I could pull all the wires that aren't ignition and then run backwards from there. Bit at a time.

Any thoughts out there?
Tom

[tomx]

With a charged battery it runs some of the time. Usually really well, but as soon as it gets hot it misfires and then cuts out.

After a couple of minutes it runs well, and gets up to speed easily but bit of traffic and it cuts out again. My friendly mechanic suggested I try a B7 plug rather than the standard B8HS.

Any ideas out there?

[arry_b]

I know you've changed the coil but does yours get hot? Poke at it with your finger when you've broken down. If should be warm, but not hot.

It's a very common problem with bikes that have been stored for some time, although whether that's the reason they get taken off of the road in the first place is debatable.

Symptoms are the bike runs OK until the coil gets hot and breaks down, then runs OK after it's cooled for a while. Then goes around the circle again.

Your battery voltages sound low too. I'd be shopping for a battery and new coil.

[tomx]

Thanks for the input.
I was worried about the coil, as I'd seen on here that they can be an issue, so I put a new one on anyway. The old one got very hot (too hot to touch), whereas the new one only gets warm. I did check when it stopped, but it wasn't very hot. I also remembered to switch off the ignition whilst it cooled down.
I have a new battery to fit, but haven't had the chance to put it on yet. The fact that it runs well after it cools down makes me think something is breaking down with heat. Whether it's electrical or petrol related I don't know.
I have a petrol leak (tap, not carb) to sort first, and then I guess I'll have to try and chase down the fault.

Thanks again.
Tom

[tomx]

I think I've found the problem.
New battery made no difference, voltage looked good and nice spark, so I tried it again. It went less than a mile and then died again.
Took it home and started draining the tank to fix a slight leak. I noticed that after a few minutes the flow stopped completely. I took the (new) fuel cap off to look at the level and the fuel started pouring out the tap.
So a vent problem. As simple as that (I hope).
All my spending on points and plugs and coil and carb were useless, and my nice shiny new fuel cap caused the problem. Guess I just need to run a small drill bit through there and make sure it allows air through.

At least I have plenty of nice spares to keep me going a while.......