Help troubleshooting an engine that won’t start

[Mcnaldo]

Inexperienced mechanic here. I’m learning through the internet and really enjoying it. My 82 CB750c currently won’t start. The initial problem arose when riding to my friends house. Suddenly I could not go over 35 and the engine would stall out when I engaged the clutch and restart when I disengaged it. I made it to his house and that’s where it stays until I can fix it. When initially troubleshooting I found the charging system was giving me less than 13volts when reving. Going through it I have done the following things.

Replaced the rotor, it tested weak
Tested the stator OK
Replaced the brushings
Replaced the ignition coils, I think they were ok but the wires were old and cracking so I swapped it out
Tested the rectifier OK

As I have been working on the bike it has become harder and harder to get it started. At first it would start but I would have to throttle it to keep it running. Currently I can’t get it to start at all. The only thing I get now is the occasional singular pop similar to a backfire.

I get a visual spark out of each plug when I test them.
My charging system was definitely weak but maybe that wasn’t fully the problem.

I’m feeling a bit directionless at the moment. Can any of you nice people steer me in the right direction?

Thanks in advance.

 

[dirtdigger]

Check compression. Probably low with tight valve clearances.

 

[Mcnaldo]

Check compression. Probably low with tight valve clearances.

Thanks. I’m on it