Check that the Lage solenoid on the Aisin reg is energising, it only operates when the distributor is turning, it's a safety fuel cut off to shut down the LPG if the engine stalls. Crank the engine and hold a screwdriver close to the solenoid armature, it shoud "grab" the screwdriver. If the solenoid is not operating the fault is in the engine speed sensor or it's relay or in the distributor ignition module. However the most comon fault I find with the Aisin reg is the valve in the primary chamber stuck with tar, this gives all sorts of strange starting problems. Because the valve when it sticks is wide open it over gasses the engine and it somtimes wont fire up. If you remove the "gas" hose from the dual fuel carb and hold it about 2 inches away from the carb connector then try and start it, it will quite likely fire up because the mixture which was over rich is now weakened. If this gets it going, you will have to strip the reg and free up the primary chamber valve........thats the chamber nearest the large solenoid...........Safety warning don't smoke and make sure you are in a fairley open area or you may get a nasty little shock! good luck Dave