I think your problem lies in fuel delivery. 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.

I found TDC on #1 by using a screwdriver in the plug hole and turning the engine over by hand. Set the static timing. With the timing set the ignition system side was done. Tweaked the carb some and got the lift to start up. A
litte fine tuning with the timing and setting the idle speed and it'll be running like a dream.

Mrfixit, thanks for all your help.

So I pulled the plugs, cleaned and gapped them. Getting good spark on the plugs and checked the coil with a spark tester and it jumped a 1/4 in. with no problem. Set the point gap. I'd like to set the timing but can't figure out how to get a view of the crankshaft pully. The only way I can think of is from underneath. but getting the lift up isn't an option I have.

Anyhow, I had someone turn the engine over while I moved the dist. around and still nothing.

Even with the timing being off I would still expect some attempt to fire.

Any ideas?

I guess the next step is to take the plugs out and visually see if they're sparking. If not then check to see if there is power to the coil and clean the points.

Compression checked out. Tried some starting fluid but don't get even a stumble. May be an ignition problem. Set the points at.018 according to specs for the nissan H20 engine, I'm assuming there's no difference on the points between gas and LPG.

I checked for vacuum leaks by spraying carb cleaner around the carb and didn't notice any increase in RPMs.

As for the valve clearences, not sure what they should be set at. I haven't been able to find any specs for this lift.

A compression test would indicate valve clearences being off, right? Bad comp. = Bad vacuum...?

You might want to check the rocker arm /valve clearances if it's running rough. That would cause low vacuum also and cause the fuel lock valve not to turn on. Maybe check for any bad gaskets on the carb and manifold too.