MEngr,
Thank you for the detailed explanation. I do have the valves set at 0.015. I will follow through the additional steps. I can only get 10 BTDC. There is no more adjustment in the slot. I've got a better analyzer on the way. So it may take me a week or two to get my ducks in a row.

Thanks again!

impco makes a lean air valve assembly for this mixer

Kingston;
The first item you need to look at is the valve adjustments hot. You should have 0.015 inches on both intake and exhaust. Item two is to set the timing of the engine to 12 degrees before top dead center with the engine's speed at 650-700 RPM. Next item is to purge the fuel system of all LPG by turning off the fuel at the tank and run the engine until it dies. When this is done go to the rear of the vaporizer-regulator and remove the 1/8 inch pipe plug and install a 10 lb pressure guage in it's place. On the bottom side of the regulator is a 5/8 plug that needs to be replaced with a manometer. When this is done turn the idle mixture screw out 3 to 3 1/2 turns and open up the fuel valve on the tank. Turn the engine over with the key while looking at the guage pressure at the regulator. You should be seeing 1 1/2 lbs plus or minus 0.5 lbs. If the fuel pressure is at the 1 1/2 run your engine till it reaches operating temperature. When the engine's operating temperature is reached put the engine at maximum governored speed full load and adjust the Power Mixture Adjustment screw to the leanest side until the engines speed starts to drop off. When this point is reached ever so slightly return it toward the "R". With all of these steps taken look at the monometer and you should be seeing 6 inches at idle and 13.8 inches water column at full throttle. Now install your air gas analysier into the exhaust and adjust idle air mixture for a 15:1 mixture. When this is completed high speed/ full power carbon monoxide reading should be 0.2% and at idle speed it should be at 0.5%.

Remove lpg mixer and place a shop rag over intake opening. Make sure that all lockwashers and nuts are accounted for and none entered intake. disassemble mixer watching to not destroy gaskets and notating orientation of components. Give all parts a good cleaning. Inspect diaphram for holes/tears if older model mixer. Make sure all orifices are cleared and rotate the lean/reach mixture adjustment full range while spraying cleaner into the inlet. Be sure to clean throttle bore well around butterfly. Do not remove butterfly to shaft screws. Just clean well around it using small brush with cleaner. Use compressed air to blow out after cleaning. Lean/ rich adjustment pointer should be one click left of midway point initially. Idle adjustment will need to be reset. Back out idle air mixture screw till maximum idle rpm is achieved. You should be good to go. That should take care of the "bad" smelling exhaust fumes also.

most of the CA-55 series mixers have a course fuel adjustment on the inlet side of the mixer. Reset your air mixture screw back to about 3 full turns out from screwed in. Then go to the course adjustment valve on the inlet and adjust this to get your best CO reading. Then you can go back to the air mixture screw and fine tune it.
If unsuccessful then replace the mixer(make sure its the same series as what is on there)

try running w/out an air cleaner,maybe a clog somewhere. valve compression?