74 Z50 no longer has spark?

Z-50 with a voltage regulator? You got a battery on that beast?

I bet what has happened is the points have closed up. The points cam is behind the flywheel and will get rust on it. Usually because the chain has come off and poked a hole in the mag cover, allowing all manner of mud and dirt and stuff into the mag.

The rust will cheerfully wear away the points breaker block (the fiber looking thingie that rubs against the cam lobe).

You can check your points gap (.020 is about right, it is supposed to break on the "F" mark) through the holes in the flywheel, but if you do indeed have a rusty points cam the flywheel will have to come off and you must polish the cam. Scotchbrite it for fifteen minutes or until you get a nice smooth finish. Dab a little grease on the felt to keep it happy.

Oh, and make sure to look at the engine case and cover to see if there is any chain damage. Sometimes you can fill the engine case damage with Bondo. The cover is best replaced, as they are pretty cheap if I remember right. $20.00 or so.

Keep us posted. :)

Try a new plug, if re-setting the points don't work.

Don't assume a new plug has no problems. I would stick another one in there & try it. Very small chance 2 plugs are bad though.

TT

MM, the 74 Z50 has no rectifier or battery. The part you are talking about is the ignition coil. It's mounted on the frame under the gas tank, right? If you have fire coming from the stator, then your points should be fine. The coils are pretty weak on the early Z50s, so I would test that next.

Follow the wire that's connected to the sparkplug and it will take you to the coil. Check the wire going into the coil for fire. If there is current going in, but none coming out, you probably have a bad coil.

If the sparkplug wire comes out of it; then that is the coil.

Again; carefully go through the points setting before replacing any parts.