This sound like it needs a tuneup?

[mr-asa]

Well shoot. Something is wrong and I can’t fix it right now.

Did a tune up, hooked up some Atom modules I have had on the shelf for a long while. Ran rough still. That’s fine, bottom cylinder is cold and nothing changes when I pull the plug wire, I pulled the flywheel and swap the polarity of the wires on the module as you sometimes have to do.
Start it up, again and it runs even worse. Pulling the plug on the bottom cylinder again does nothing.

Time for a compression test or something, I guess. Dadgummit.

[outbdnut2]

It could be as simple as a bad spark plug – some are bad new out of the box lately – especially Champions. Try swapping the spark plugs and see if the problem moves to the other cylinder. You can also swap coils and condensers to see if the problem follows the swap. Spark plug wire could be bad too.
Dave

[billw]

Compression test followed by an open gap spark test. It’s just good to know it will pass those two tests, even if it is just a bad plug. I know some of you guys like those modules but the old points and condensers are just so simple and bullet proof……To me, the modules just add some uncertainty where there really is no need to add it. Just my own opinion. The other thing, after those two main tests, for me, would be to bring out the cheapo KV meter and/or inline neon spark checkers. My under-$100 KV meter has solved more mysteries quicker than almost any other method I can think of.

https://www.ebay.com/itm/114895532985?hash=item1ac04eb3b9:g:M-gAAOSwVJ9g8yAa

Long live American manufacturing!

[mr-asa]

Compression test looks good (90ish on both) ended up swapping plugs and got great results, slight stumble, but I was able to adjust that out a little bit later.

Took it out on the lake and ended up with it running as bad as it had before I did the plugs. Ended up having to screw the idle screws in almost to closed to get it to run halfway well. I think the retainer nuts that go around the idle screws were too loose? I didn’t have a wrench to tighten them.

https://www.youtube.com/watch?v=OOD97JkbSgQ

[mr-asa]

Testing in a barrel today after I tightened the retaining nuts. Runs great. Brand new fuel pump doesn’t keep up with it
One of these, which is advertised to work with a 25HP https://smile.amazon.com/dp/B08D3LF9FB

[Author]

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