Weak battery? No spark?
 

I've charged the battery up and it turns the engine over fine, but I get no spark or volts on the negative post on the coil. Could this be caused by a weak battery on this 128?

Ive replaced the V/R, coil, condenser, solenoid, new wire harness.

It had spark last week but the coil was going bad so I replaced it now no spark.

The battery is 3 years old

Do you have power on the + side of coil with the key turned on?

Can you see spark at the points?

A low voltage battery can cause a no or weak spark. BTDT.

Click on this link and with a DVM or VOM, you can trace the issue down....... Diagram

I am no expert but could there be a problem with your ignition switch? That is about the only thing you did not replace.

Great point Paul. Kinda what I was thinking. Looks like the points weren't replaced yet either. Maybe a quick clean with some emery cloth would help.

I have a new set of points laying around, ill replace them today.

Ignition switch was replaced with one off of another cub but its still could be bad.

12v power is going to the positive post on the coil.

IF you have 12VDC on the ( + ) and ( - ) side of the Ignition Coil and still have no spark, I would look at the Spark Plug Wire and/or the Spark Plug itself. This is assuming the Ignition Coil is working correctly.

I dont have 12v at the negative post when I crank the engine, only the positive.

Take the neg wire off the coil and see if you have 12V.@ the coil with key on and/or cranking,
if so, then the problem is in the points/condenser or shorted wire to them.

Here is a quick test you can perform. Take everything off the negative Ign Coil Term. Install a jumper wire on that terminal. Turn on the Ignition Switch. With the opposite end of the wire, touch the motor block (ground) momentarily, if all is well, you should see a small spark at the end of the wire and spark at the Spark Plug.

http://i176.photobucket.com/albums/w...COILTEST-A.jpg

OR.....

Take everything off the negative Ign Coil Term. Turn on the Ignition Switch. Take the black or negative meter lead and attach to motor ground. With the Red meter lead, if all is well, you should have 12V at both the positive and negative terminals of the Ignition Coil.

http://i176.photobucket.com/albums/w...COILTEST-B.jpg