Early AS-400

Vent Tube connects to crankcase w/ internal valve. Crimp on fuel line, light gray paint, 2 piece snorkel, no raised surface for tank side screws, "T" shaped starter handle, internal muffler, cylinder top is capitol dome shaped, spark plug boot does not cover all the porcelain, intake elbow is the same size on both ends, ign coil is black, carb has 2 adjustments.

Late AS-400

Raised surface for tank side screws, fuel valve on tank. Intake elbow has built in channel. Later AS-400's reverted back to original design, plug boot covered all the porcelain on spark plug.

Early AS-450

Early AS-450, Carb Atmosphere Relief Tubing connecting from base of Carb to Elbow behind spark plug. Vent tube connects to both chambers of tank, no internal muffler, intake elbow larger at tank end, "L" shaped starter handle.

Late AS-450

Anodized Finish, cylinder has 2 flat surfaces leading to spark plug. Ignition system change to tan, cream or brown colored coil.

AS-500

Basically the same as Late AS-450 but had a 1 piece valved snorkel.

Late AS-500

Tank was polished, no seam lip.

Early AS-600

New polished tank design with seam lip, new carb with 3 adjustments, black starter housing, prop guard and intake elbow, upgraded to electronic ign system.

AS-600 CE

Same as above with add safety features to water inlet, prop guard and addition labeling. Tank color is now green.

AS-600 EPA

Same as above but reengineered to meet U.S. E.P.A. emission requirements. Cap locks on carb adjusters.