Sea Foam will make it smoke blue..... How much did you add? That is probably the smoke.
Kick the premium gas. Use regular
Pull the tank, flush it out. Pull the carb and clean it. Tune it up: Spark plug, plug wire, points and condenser. You can file the points if they are still in good shape instead of replacement. Pull the head, decarbon the top end, plane it and install a new gasket. Time the ignition system. Tune the carb. I'd also suggest changing the rear end oil too.
Here are some threads to help you out:
http://www.onlycubcadets.net/forum/s...ead.php?t=4376
http://www.onlycubcadets.net/forum/s...ead.php?t=5656
http://www.onlycubcadets.net/forum/s...ad.php?t=33461
Let us know how it goes.
