For about 7 years I ran my mower on Propane . When fuel injection first came around Ford was trying something along the idea of the GM throtle body, but with 500 wires and hoses, the book said to set that mess you used a propane torch (not lit) held in the carb to keep it running.I mention this to let you know were I got the idea it was that simple. Back to my mower. I used the 20 pound tank and regulator from the grill and I drilled a hole into the air cleaner big enough to get a hose forced into it .Started my mower on gasoline and slowly turned on the propane bottle till the engine started to load up on fuel like the choke was on. Turned off the gasoline and waited for the carb to run out of gasoline. I had to turn on the bottle a little more as that happened. Then I pushed the throtle wide open and engaged the mower deck and turned on more propane till it sounded steady and mowed. The valve in the 20 pound cylinder is really hard to use for adjusting the fuel for rpm ratio because a 1/16 th of a turn is a lot of propane for a little engine. I bought a small brass valve at the hardware store that was a lot easyer, took a whole turn to get from idle to top rpm. After 7 years of that I bought a two stage negitive pressure regulator off EBAY . For me to add this to my old set up I had to remove the regulator that was from the grill and the hose from the grill as it was only rated at 1 pound and the bottle of propane can get as high as 250 psi.So I bought two reusable hose fittings and a few foot of propane motor fuel hose off ebay.Connected the hose to the propane bottle and to the new negitve preasure regulator. All connection after the regulator are vacuum. Mine has a small 1/4 inch hose to the manafold side of the carb, this is a fuel shut off saftey valve. If the motor dies it shut down the propane from the regulator. Again if you are looking at the carb this hose needs to be on the engine side of the throtle butterfly to maintain steady vacumm. The last hose is to the air cleaner or hose between the air cleaner and carb, as long as you get on the engine side of the filter element to get some intake vacumm. This regulator allowes me to start on propane and idel or shove it wide open engage mower deck and the govenor works fine , no playing with the valve. pretty much like running on gasoline other then no choke. At any time I want to run gasoline I turn off the propane bottle and turn on the gasoline valve. Most floor polishers and smaller engines like genset use vapor regulators and that is what I used, manual say 40 hp max. Larger engines use a regultor /vaporizer that heats up the propane to convert it from liquid to vapor, reason for this is as you pull propane from a bottle it tends to want to freeze up like a aircondtioner and larger engines will pull more vapor then the tank will give with out turning into a snow ball. At this time I still have my Toro GM72 that has the Continental 4 cylinder and my Case/Davis Scatback430 loader with the Wisconcin V4 converted this way. I would be glad to take some pictures of this if anyone has a interest in what I have done. I could not find a lot of help on this type of thing when I did most of it. It is 110 octane so you could put in a thin head gasket or mill down the head but will your starter crank it, it does burn slower then gasoline so we should ****** the timing to lite it up sooner to get the bang on top, I think they make a offset flywheel key to do that. Once mine started and ran so good I never went on.
