1960s Sears Clinton 3.5 Running rough

[atucker1]

I recently posted a thread trying to get my Sears 3.5 running. I was successful and took the motor out for a roughly 30 minute trip. There and back it was fine. I stopped for a little while and then continued running it. The motor then started to misfire (if that's the right term) occasionally. Since fuel was starting to run low, I tilted the tank so that there was definitely plenty of fuel. This did not help. I stopped the motor, waited a while, and started it up again. It ran extremely rough. I was able to get home at idle speed, but if raised above that the motor gets rougher and rougher. Today I tried a different spark plug and adjusting the carb settings. No luck. Also, the motor seems to be smoking more than usual. This is a video of the motor showing the condition: http://youtu.be/rr_JxNy_NaI
The audio doesn't capture the sound very well. The best way I can describe it is that the motor (when working correctly) hums, it started popping occasionally the other day, and now at idle it hums and pops, and at higher throttle it just pops.

Thanks in advance for any input!

 

[brim_buster]

What did the spark plug look like when you pulled it? Could be trash got under the needle and its running rich. Its a thought. Fuel pump diaphram could be weak or have trash in it. Points could be out of adjustment. Hard to say. Its one of those process of elimination things.

 

[atucker1]

No Title

Definitely running rich but I swapped in a clean plug and had the same problem with the carb setting on lean. Pulled the flywheel and will readjust the points--I suspect that's it since I fiddled with them trying to get it started and only had a ruler to re-gap them. Confuses me why it took a while to make it run rough though.

 

[atucker1]

It was the points. I re-gapped them and replaced the flywheel and it runs smoothly again. I opened the points up to a little bit more than .020. Also, it starts a lot more easily than before. Thanks for the help!