I see no reason it cant be done, and with a much better setup than that. Just consider the fork lifts that run on propane. Would be a nice winter project if it does at least run as cheaply as with gasoline. Of course it would be limited to 4 strokers I would think.

Crude but cool. It's been done before. My neighbor showed me a factory propane conversion kit he had in a box for a Clinton engine.

Thanks for the link, Tom. Hopefully some engineers from Briggs or Tecumseh will read it.

I'm all for developing small gasoline (and Diesel) engines that can run on alternative fuels---anything to reduce our dependence on foreign oil and the unstable governments where it's produced.

Tarheel
I can see where diesel engines are not popular with the mower manufactors.

Take this Hatz diesel engine for example.

# Model 1B20 9901
# Air cooled, 1-cylinder, 4-stroke, direct injection engine
# Die cast crankcase; pressurized lubrication
# Recoil start; 3600 RPM
# 3/4in. x 2 7/16in. shaft; 3/16in. keyway

HP = 4.6

Cost = $1339.99

I would hate to see the price of a push mower with a 5 hp diesel engine.

Here is a link that might be useful: Hatz Diesel engine

Not to mention that engine alone weighs in at a hefty 73 pounds! Imagine that on an already porky Snapper!

If i remember correct you need a harder exhaust valve, maybe seat? Also the govenor would have to have a special regulator, During the last gas shortage lots of sevise vans with small block chevy's were converted over to propane, haven't seen one of those in years.....and gas prices never came down, just supply meet demand...so i would surmise they are NOT pratical ? WDIK

In the 80's when I was going to school, our school district had the busses converted to propane.

I like the disclaimer from the website's directory:

Anyone reading this web page should not assume that any given subject is safe or legal. The purpose here is to give information only. I take no responsibility for what anyone may do with the information given here. What you do with it is your own business and responsibility. Building some of the projects, described here, can be dangerous, illegal or both; and require that the builder or user be very conscientious and able to exercise a great deal of Caution and Common Sense. A project described as "relatively safe" may not be completely safe. It may be described as "relatively safe" only because it appears to be safer than making a batch of Nitroglycerine. Never get cocky where safety is concerned.

Hippy--

Thanks for the link. Weight and cost are definitely issues with small Diesels. Hopefully, some engine manufacturer somewhere will spend some R&D money to overcome these issues.

Propane has its own issues but, here again, it'd be nice if an engine manufacturer would invest in an R&D project to overcome propane's issues. It'd help us break our dependence on foreign oil.

Those of you with E85 (85% ethanol) stations nearby could run any of your older 4 stroke engines on it. I've run it in my Ariens GT17 with great results. You just have to open up the jets a bit, as E85 runs on a stoichiometric air fuel ratio of 10:1 compared to gasoline's 14.7:1
Cold winter starting may be a bit of an issue with low compression engines, but I'm sure there's ways around that too.
Right now E85 is under 2 bucks a gallon here, and it burns nice and clean...No plug deposits, and a kind of sweet "Indy Car" exhaust smell.

E85 is hard on neoprene gaskets, O-rings, and seals, but so far I haven't had anything fail on mine...They say it's corrosive to aluminum too, but that remains to be seen as well. I've noticed no abnormalities.

Jetted correctly, I believe E85 makes more power than gasoline, but haven't confirmed that with any real data. Just tilling the garden with the GT17, the thing felt unstoppable! It also had a cool looking blue flame coming out of the exhaust when put under heavy load then backed out quickly.

The engine didn't seem to be running any hotter, and it starts quickly just as it did with gasoline, even when cold...Just have to baby the choke a little more till it's warmed up.

I and my partner refine used veggy oil for use in diesel engines.We also do the conversions in the shop. It's starting to become popular since the cost of fuel spiked.

EnviroGard has a line of propane mowers and certified conversion kits available. www.envirogard.com

Here is a link that might be useful: EnviroGard Propane Mower

Propane is very practical on a car or any liquid-cooled engine. I think it actually provides more BTU/gallon that gasoline, but also has higher octane (104 or so, I think) and therefore requires more compression and/or timing and/or boost advance to realize that latent power at the crankshaft. On an air-cooled engine like a mower, I would expect difficulties with the propane orifice freezing closed at some point or else the carb venturi building up ice and closing down. On propane conversions, the carb is actually heated by coolant water to keep this from happening, but that's not so easy to do with an air-cooled motor. Of course, if you could get it to more of a direct injection situation, then heating wouldn't be needed and you could also realize a lot of extra power from the charge cooling effects of the vaporizing LPG. I don't know how they do it, but floor buffing machines are often run with propane engines that must have a lot in common with mower engines (because they run inside they can't use gasoline or diesel). So there are systems out there that are probably adaptable to lawn equipment use. Plus, I'll have to read the links to these conversion companies because they've obviously figured it out.

Propane on a air-cooled engine is definitely doable. I set up a Honda engine to run this way. I have plans available if anyone is interested.