A follow up to my last post.

I really think that your low end needle is WAY to rich. That will keep the engine running forever at low throttle settings. Burbling on throttle up is a good sign of richness. A high oil content will foul the plug quickly and make for a rough running engine. Stay at mixtures at 60 to 1 and aove and see how that works.

Run the engine at a mid range throttle setting and tweak the low end needle for max rpm, then richen it up about 100 rpm. Then set the high end needle with a tach for max, and richen it up a couple of hundred rpm. Tweaks after all this should not be more than 1/8 turn on either needle for elevation and weather changes.

Use a well balanced and light wood prop (22/8 or 22/10) to get instant throttle response when you are setting up the engine. After it's set up, use whatever prop you want but leave the needles alone.

Talking to CH, the ignition air gap should not be a problem. I have to say that my other 3.2 that I have been running for over a year now has the same air gap and runs very well, indeed.

Brison makes a very good engine. I'm certain that the problem is a minor one.