Just wondering if there is a vacuum line on the Magna that you can pull. That will allow you to suck some Sea Foam into the cylinders. Very simular to what we do with out cars an trucks. I was thinking of maybe the crank case line as it is very handy an out in the open.
I use Seafoam to unclog carburetor jets. Perhaps it has value in the cylinders, but why would you bypass the carbs?
I run it through the carbs also to clean the jets etc. I was wondering if there was some way of getting it into the cylinders. So you can over does them to clean up any deposits that might be built up around the rings,cylinders an valves.
under each intake rubber boot is a screw, except for the front right carb. you can order those 'booster joint' i think they are called that has the vacuum line to the fuel shutoff valve on it. you would take the screw out of each one and screw in those vacuum port 'booster joints' and then you can feed a tube from each port into a can of seafoam and clean the valves and intake ports.
Dump some down the spark plug hole.