Outdoor Power Equipment and Small Engines - Briggs & Stratton Magnetron problem?

The right-hand cylinder on my Briggs & Stratton 18HP twin engine (model 422707, type 1211-01) appears to be cutting out intermittently. I have measured the spark going to both cylinders. The spark on the left-hand cylinder seems constant and strong, jumping a gap of approximately 3/8 of an inch. The spark on the right-hand cylinder is much weaker, only jumping a gap of 1/16 of an inch and somewhat intermittently at that. It would seem that the Magnetron is faulty but before undergoing a rather costly replacement (in expensive Canada), is there anything else I should consider? I gather that Magnetron failures are rare so maybe I'm barking up the wrong tree.

It sure sounds that you have a failed ignition coil but to be sure you need to remove the kill circuit wire (small gauge) from the coil, be sure the coil to magnet airgap is correct (.010") and then check for sufficient spark. If not then it's time to replace the coil.