Converting a Generator to Run on Propane




A step by step instruction on how I converted my generator to run on propane as a back up fuel source. There a numerous reasons one might want to do this. You might need a cleaner burning engine. You might not want to store or carry large amounts of liquid fuel around, besides liquid fuel eventually goes bad, propane will not. Its easier to store large amounts of propane. In an emergency situation such as hurricanes and earthquakes, gasoline might not be available or if it is, it will be in high demand, propane usually is not.

I found several ways of doing it on the web but nothing that seemed permanent or cheap. They have kits to do this but I didn't feel like forking out 100+ bucks to do it. This project cost me about 25 bucks and thats because I wanted new parts. If you had the parts laying around you could get out of it cheaper.

Step 1: Warnings

WARNING This could be dangerous if the motor dies and your not around, the propane will continue to run and could possibly build up and you would have a nice explosion. The kits available commercially have a safety shut off or an on demand regulator that will shut the gas off when the engine dies or is not running so they will not flood the area with propane.

I run my generator outside on the driveway and know when it dies so I don't have a problem with the way I did this. Besides, with the wind blowing, I would never have a problem with gas build up. NEVER run the generator indoors with propane or any other type of fuel for that matter. Propane is heavier than air so it will collect on the floor or near the ground when it is allowed to escape out of the tank. Use this instructable at your own risk!!

Step 2: The Carburetor

I used an old carburetor off my kids Go-Kart. It was shot and not repairable. It was physically the same size as the carb on my 10 hp generator and made by the same company. If you decide to use the carburetor off your engine be aware that this process is not reversible and it will make the carburetor totally useless for any other purpose. My advice is to obtain an old carb to convert for 3 reasons.

One, if you screw it up and it doesnt work, then you still have your original one to put back on your engine.

Two, if you decide to later return your engine to operate off gasoline, it only takes a min or two to put the old carb back on.

Three, you will have a way to run your engine on two different types of fuels. Could be useful in a crisis when gasoline might become scarce.

You can obtain old carbs possibly by visiting a local small engine repair shop. They might give you one cheap if it cant be used on a gasoline motor anymore. Another source is to look for the same type of carb or engine that has a carb, on an old mower or some other engine that doesnt run anymore. Look on craigs list, garage sales, ebay, neighbors backyards, trash dumps etc etc... any carb that will physically fit your engine should work for this even if it is gummed up from gasoline. Possibly if its from another mfg, just as long as the mounting flange and openings are the same.

Step 3: Remove the Old Float and Needle Valve

You first have to remove all the old parts out of the carb. First remove the bowl. Usually this can be done by unscrewing the bolt or jet on the bottom of the bowl. As you can see, this carb was pretty old and totally shot.

Next remove the float and the needle valve and spring. Most carbs you just have to remove the pin that the float hinges on and the float and needle valve come out all connected.

Step 4: Remove the Butterfly Valve

Next, remove the butterfly valve and its shaft. This is done by removing the little screw on the valve plate itself and then the shaft just lifts up and out.

Step 5: Remove Idle and Mixture Screws/jets

Remove the idle and mixture screws/jets. These wont be used for propane. You will end up using the new needle valve we will install to control the RPM of the motor.

Step 6: Removing the Jet Hole Plate Cover.

I suppose you could leave this on, but I wanted to make sure these holes under this cover where plugged.

How I removed it was to first drill a hole in the cover. Be careful not to drill through the carb, just drill through the small aluminum cover. Then I installed a screw into the hole and then screwed the screw into the hole until the cover popped off. Not sure if this works on all carbs but it worked great on the one I have.

Step 7: Primer Bulb Removal

On this carb I was able to just pull on the bulb real good and it popped right off. There is a small retaining ring that may have to be pried out before removing the bulb. My ring was rusted so bad it just popped out when I pulled on the bulb.

Step 8: Venturi Jet Removal

You have to remove the venturi jet. Install a screw onto the center of the jet from the bottom and then pull. The jet assembly should come out. If not don't worry, in a later step you will drill this out but I thought it would be easier to remove it before drilling.

Step 9: Clean It Up

Now clean the whole carb up. I used my dremel tool with the wire wheel attachment and a small wire brush. You could also use carb cleaner if you wanted to also.

Step 10: Drill Out the Venturi Port

Next you have to drill out the old venturi port to accept the 1/4 tube you will install later. I used a 1/4 inch drill bit.

Be sure to drill straight.

Be sure to remove ALL metal shavings out of the carb. Any shavings left might be sucked into your motor!!! I used a chemical cleaner and cleaned it after drilling.

Step 11: Seal It Up

You now have to seal up all the holes and jets. I used the black ATV silicone you can get at the auto parts store. Its heat resistant and seals good. Seal every hole and jet you see except the main venturi jet. Even seal up the old gas supply connection. Seal up the primer bulb hole as well. I ended up removing and sealing the vacuum control hole as well, this is the small nipple seen in the second pict.

Step 12: Parts for New Venturi Tube

You will need a BBQ grill regulator. I bought a new regulator assembly for a BBQ grill at Harbor Freight for 15 bucks. I'm sure you could get one off an old gas grill. I then used a 1/4 inch copper compression needle valve, a 3/8 flared to 3/8 male pipe thread (MPT) adapter and a 3/8 to 1/4 inch compression reducer to make the connection to my propane regulator.
What ever you end up using, reduce the connection down to 1/4 inch to match the new needle valve. This valve will be used to adjust the gas flow.
You will also need about 6 inches or so of 1/4 inch copper tubing.

Step 13: New Venturi Tube

I used a 3 inch piece of 1/4 inch copper tubing for the new venturi tube. When cutting copper this small, its good to deburr it after cutting so the burr wont interfere with the gas flow. I used a small file to remove the ridge inside and outside of the tube after cutting.

Step 14: Venturi Assembly

Assemble the venturi assembly as show in the picture. Its pretty basic. I used Teflon tape on the connections and made sure they where tight. I used another piece of 1/4 inch tubing between the needle valves and adapters. This piece of tubing could be as long as you need it to be.

Step 15: Put It All Together

Now slide the venturi assembly into the carb. I found that the venturi placed inside the carb about 3/4 of the way into the carb opening worked best for my motor. If you can get away with test running the motor first before epoxying the assembly to the carb, do it. I was able to slide the assembly up or down until I found that 3/4 of the way worked best. Cant explained why, it just work best placed 3/4 of the way into it then any place else I tried it. The first picture was taken before my test run. The second picture showed the position of the venturi after the test run.

**Update I figured out that the engine was getting too much air and this is why the engine ran better with the venturi in this position. I have since added a restrictor plate to the air intake as you will see in the video.**

Step 16: Mount the Carb Test and Final Assembly

Mount the carb on the motor. Be Sure to use a gasket between the carb and intake manifold. Connect the gas regulator line to the assembly and connect to a 20lb propane tank.

To start the motor, make sure the needle valve is turned off. Turn on the gas on the propane tank. Turn the needle valve about 3 turns and then quickly pull start the motor. After 2 pulls mine starts up and then I can adjust the running speed by using the needle valve. If it doesnt start within a couple of pulls or you start to smell a strong oder of gas, turn off the gas and let the area clear before trying again. Just watch for gas build up. Do it outside in the driveway.

When it starts adjust the needle valve for best running speed. You may need to slide the whole assembly into or out of the carb to find the depth the venturi needs to be for best results. After you find this spot, mark it on the tubing and then using marine epoxi or jb weld or some other high temp epoxy, epoxy the whole assembly where the venturi tube slides into the carb.

As soon as the weather clears up I will attach more picts of my final assembly and maybe a video on how well my motor runs and how I start it.

Step 17: Final Setup and Run

After messing around with this set up for a week or so, I discovered that the engine was getting too much airflow. I ended up making what I call a restrictor plate to restrict the airflow. In the video you will see the plate I made. I just mounted it to the front of the carb with one screw and adjust it according to the weather, colder weather I will have to restrict the air more, warmer weather I will have to open it up some. I set the plate so that the governor of the motor "floats" in the middle of its travel. On a generator you have to get it up to a certain speed for maximum power and frequency generation, without a tachometer I figured if the governor was about in the middle, it was running about the correct speed. Load tests of about 35 amps confirm the generator is able to deliver what it is supposed to without the motor dying or any other problems. It does load up but it never died. It was mentioned about the lines freezing up in one of the questions, I was not able to see any ice or signs of freezing, but the temp was about 20 degrees when I tested this thing. I don't know what it would do in warmer weather. I let the thing run for about 2 hours with no problems. I also did away with the 90 degree elbow I mentioned earlier. I did not like the way the 1/4 inch line vibrated with the elbow on, so I ended up as you can see in the video just making a gental sweep into the carb.



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    165 Discussions


    6 weeks ago

    Good idea. But for people going to use this setup. You must use a multimeter to set the rpm so you get 50hertz and the correct voltage. Different rpms will change voltage and hertz


    1 year ago

    Forgot -- 6.5 hp clone Honda Make'em for larger engines also..


    1 year ago

    I've played around with Propane on several things. Used it as a starting fluid from a torch when an ATV had old fuel and ran the ATV for quite awhile with the small bottle dialed down. I have since worked with DIY conversions.

    I am working on building EFI for my mower but Propane is much more efficient and simple without building a chip. I am learning piece by piece of info about fuel weight/flash point/separation from my dad who's an engineer at a refinery. It's interesting how raw petrol is separated based on weight.

    Having a gas disperse rather than hazardously liquify on the engine seems safer.

    Stick a small propane bottle unlit in a small engine and slowly turn the fuel on while it sparks. You can eliminate a carb and go straight to a custom intake manifold but need a simple means to adjust air:fuel.


    2 years ago

    I notice a 'detractor' or 'troll' in the comments below, describing all the monthly damage to engines running LPG. That person is a liar, an idiot, misled or just plain ill-educated and completely wrong ! Such damage may well occur in the engines he mentions, but it is certainly NOT from the use of LPG as the fuel.

    LPG is Liquid (or Liquified) PETROLEUM Gas and is a close relative of the petroleum (gasoline) used in our motorcars (automobiles), hence, being gaseous in the first place is actually LESS damaging to the mechanical parts because is DOES NOT wash off the lubricating oils when fuel rich and DOES NOT cause the same levels of carbon deposits, due to more intimate mixing of fuel and air.

    I don't like the method described above for the conversion because it almost certainly is inefficient with the propane and fails to automatically control the fuel based on engine demand. If there is demand for it, I will produce a video on how to make a demand valve so that an efficient and safe system can be made for very little money and without needing the silly spare carburettor !

    1 reply

    Reply 1 year ago

    10 hp is not going to supply 35 amperes either.

    Ebenezer ScroungeChrisD201

    Reply 2 years ago

    Keep in mind, hydrogen can actually leak through metal. It also makes metal tanks brittle. Expect to lose 1% per day.


    Reply 2 years ago

    It certainly can. The only problem is fuel availibility. It is tough to source. That being said you are probably thinking of making hydrogen from water, an inefficient proposal.

    Electrolysis of water its more like a battery than a source. It is a great way to store energy, but only if you can find an efficient method of converting it back to water.

    If you had other ideas, i apologize, please share! If im correct, start looking at fuel cells.


    2 years ago

    Just a comment about the gases. If you use butane in your camper or caravan (trailer) instead of propane, the same systems work but the regulator has a different connection thread. I noticed someone ask about methane. Engines run just as happily on methane although if the source is from domestic pipework, the pressure starts quite low (compared to propane and butane in bottles). During WW2, my father and many others ran their cars using Towns Gas which was the domestic gas in UK prior to conversion to methane. They simply filled a large balloon on the roof of the car with the gas and this was enough to get to work and back again.

    Hope that it useful :)


    4 years ago on Introduction

    Wouldn't it be simpler/cheaper/easier to put a modified flange instead of gutting a carb, and running the needle valve and piping to that?

    you could put a ball valve on the supply side of the needle valve for quick shut off, would give you instant backwards compatability, and you could start it on gas then switch over to gas once it's warmed up for easier starting. Would also allow you to hook up to NG at your house, you'd just have to readjust the mix for NG vs. propane though.

    2 replies

    Reply 4 years ago

    It would be cheaper just to drill a hole in the breather filter housing and stuff the hose in there but I wouldn't have repurposed the old carb that was heading to the garbage... that was one of the challenges to keep the old carb from becoming landfill fodder


    Reply 2 years ago

    How large of a whole has to be drilled, to be a suffishent port of gas flow.


    2 years ago

    Lived off gridd for 11years in the Australian desert and ran a small petrol motor on lpg to power a big industrial evap cooler .
    Worked well.


    2 years ago

    How does a professional conversion work? This or other unregulated methods would work in a pinch. But without the governor/butterfly assist you'd loose the ability to operate under widely varying loads unless you plan to constantly fiddle with the restrictor plate and flow valve.

    Even a method involving a safety cut-off and retaining the butterfly/governor functionality is hindered without the ability to regulate gas flow based on demand.
    It would loose a lot of power under load and possibly detonate/pre-ingnite (governor demands more air, leading to too-lean condition), or run way too rich under low load if the flow were set for optimum high load conditions.

    So how does a professional conversion work? Do they somehow regulate flow based on the governor input or vacuum sensing or something? And are they adjustable? Because most I'm seeing for sale say they work on a large range of engines, so without a mixture adjustment they could be wildly out of tune as well.

    Love the homemade solution in a pinch! Just trying to understand whether there is any advantage to a professional kit, or if they too are just something that "works" rather than something that works well.


    2 years ago

    you can get a vacuum diaphragm safety switch that will only let the propane flow if there is vacuum from a running or cranking over engine. such as this and it needs no power to run. I have one on my pressure washer and am using one on my generator install.


    4 years ago

    I like the idea of multiple fuels now only if it would run on methane

    1 reply
    pmuhammad dwikelms1

    Reply 3 years ago

    nice idea, but methane are less flammable than propane...
    you need to adjust at correct proportion


    3 years ago

    Why not just use a Makuni type of carb, seal off all the holes, keeping the slide and metering rod in place. Plumbing the feed up through the center as before, but instead of needing a butterfly to regulate the air fuel ratio it would pretty much be done internally. Well, in theory anyway. But good job. Thank you for the post.


    5 years ago on Introduction

    I was really on the verge of giving up on deciding about using propane conversions but I think somehow I found the answer. I am a newbie here but I would just like to share my experience since some people might feel the same way. At first I was a bit doubtful if converting gas to propane would really fit my expectations but I've come to realized that yes, it is the answer for my longing prayers. It's very affordable, convenient and is truly a lifesaver. I don't need to spend too much on gasoline and I enjoy the perks of saving my precious time and energy. Just to share, try visiting this website that I found, It's a good reference for your concerns about propane conversions.

    I hope it will help you like it did for me. :)