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Like Frank says, there are numerous “fixes” for these early engines, and some of the cams were matched to the replacement carburetors. The cam without the steep ramp looks like the original one, which I would try first…The cam with the steep ramp makes for some odd midrange running characteristics. As for the different cam pick up points, I wouldn’t worry about that either…Set it up according to the original mark and try it….Advance the throttle pick up a bit if the engine seems rich off idle, retard the original setting if the engine is lean/bogs off idle/acceleration.
I have oftentimes been confused by these engines, the early ones (with all the plug fouling issues) seem to run the nicest at low speeds, maybe it is just me…So, I am inclined to use the early stuff, and those NGK plugs (never tried them myself, the Champion UL81Cs seem to work fine) everyone raves about….Let me know how you make out….
PS Does this thing have the updated head? I wonder if the inner exhaust housing was modified, this fix involved drilling a few exhaust relief holes at the top to relieve back pressure.