[ceslaw]

Caprimaniac:

Temps are F, not C. But use the temps as a relative indication, not an absolute. Different engines will have substantial differences in 'normal' operating temps for the exhaust gasses.

I assume timing is right, getting spark to all the plugs, and only issue is carbs.

Are the two non-firing cylinders on the same carb? If so check the air flow to make sure it is flowing the same as the other carbs. You might try to open the idle stop screw on the problem carb just slightly more than the other three to see if that will get it to fire. That would tell you it is indeed a carb issue.

Of course you need to do all the preliminary checks: linkage working properly, floats properly set, clean idle circuit, etc.

Experiment with the mixture screws. There is a 'sweat spot.' As you back it out you may find it suddenly firing - back it out a bit more and then fine tune it.

I don't suscribe to the notion that all eight mixture screws must be exactly the same and less than a single turn out. Get it running right, and if one is out a half turn or three fourths of a turn more than another don't worry about it. Of course if all the mixture are more than a two or three turns out you lilely need a larger idle jet.

At this stage the temp indicator will tell you whether it is firing or not. Don't rely upon the temp readings as you primary means of adjustment.

Good luck. Patience . . . . .