Introduction: Multi-Fuel Generator - Gas Propane NG

Picture of Multi-Fuel Generator - Gas Propane NG

Generators are a wonderful convenience when the power is out - unless you have no gasoline. Then they are a huge paperweight and an annoying reminder you should have had more gas on hand. This conversion is very fast and allows you to run your generator on gasoline, propane or natural gas - and easily switch between the three.

On June 29, 2012 Virginia experienced the blunt force end of a derecho - a freakish fast moving destructive thunderstorm. One of the worst in recorded in North American history. People died, houses burned, trees fell everywhere taking power lines with them. It even disrupted Instagram, Pinterest and Nextflix (gasp) when Amazon's Northern VA data center was offlined. 2.6 million households lost power in Ohio, West Virginia and Virginia alone. My house lost power for 10 days. It was hot, we had an infant and most gas stations had no power to pump fuel. The stations that did have power were often sold out. We made it through with the generosity of family, but it made me take a serious look at my storm preparedness. It was clear I needed a larger generator, better extension cords and more fuel storage.

Gasoline storage is sub-optimal. The majority of pump gasoline is full of ethanol. Ethanol fuel goes bad quickly and really should not be used in small engines. Non-ethanol gas storage needs to be rotated. My prepper friends do a much better job of this than I do. I get lazy and I forget. Plus at $3 or more a gallon gasoline is expensive.

I wanted a better more versatile answer. I also happen to have a very full 100 gallon propane tank only hooked to a set of vent free gas logs. Since I heat my house with wood these are only used as a backup heat source. Currently I can get propane delivered to my house for $1.89 a gallon. Plus I had a few grill tanks hanging around that I picked up (partially full I might add) for $5 each.

There was my answer. Propane was cheaper, easier and safer to store.

My house does not have a city natural gas hookup. However if you do you are in an even better situation - no storage necessary!

Step 1: The Essentials

Picture of The Essentials

There are two essential pieces to a conversion:

  1. On Demand Regulator AKA Zero Governor
  2. CarburetorAdapter

I've seen a lot of very bad unsafe conversions - mainly ones that skip the on demand regulator. This is device is crucial to safety. There is a vacuum valve inside the body that only allows fuel to flow when there is suction on the outlet. As your engine spins it creates a vacuum that draws in the air and fuel. This vacuum demand opens the valve on the regulator and allows fuel to pass. If for some reason you engine turns off the flow of fuel would immediately stop. While it is possible to just stick a propane line in a carburetor and spin it over - it is a very very bad idea.

The carburetor adapter is device that is placed between the carburetor and the air cleaner. It allows for the injection of the propane or natural gas in to the fresh air coming from the air filter and into the carburetor.

I wanted a tri-fuel adapter and not a conversion kit. I want the flexibility of being able to run on three different fuel types.

Step 2: The Kit

Picture of The Kit

I've seen several kits for sale. I think I got a very good deal from US Carburation. They are switching their adapter style and they sold me this kit for $128 shipped from their eBay store. This being my first conversion I wanted a commercial product. I'll probably play around with my own adapters on other engines.

Included in the majority of the kits are:

  • On demand regulator
  • Carburetor adapter
  • Carburetor gasket
  • Stud extensions
  • Mounting bolts
  • YELLOW Teflon tape or thread sealer
  • Hose used between on demand regulator and adapter
  • Fittings used between on demand regulator and adapter

Step 3: Not Included

Picture of Not Included

This was a very inclusive kit - but there are a few pieces that are not included.

  • Low pressure regulator $9.99
  • Threaded tank fitting - gifted from dad's pile of I'll never use it again.
  • Hose between the low pressure regulator and the on demand regulator - gifted from dad again.
  • Fitting between hose and on demand regulator $2.69
  • Cap for when no propane hose is attached $1.09
  • Fuel tank - $5 gas grill tank from Craig's List
  • Propane - $1.99 x 4.2 gal.

Additionally I added a 1/4 inch ball valve between the carburetor adapter and the on demand regulator. I did not want to be pulling a vacuum on the diaphragm when it was being used with gasoline. ($7 big box store)

Check a local camper supply store for the fittings, regulator and hoses you will need. They will be more knowledgeable and easier to deal with than a box store. Mine was also cheaper with a much larger selection.

Step 4: Remove Air Filter

Picture of Remove Air Filter

Remove the air filter cover and air filter.

Step 5: Remove Filter Housing

Picture of Remove Filter Housing

Remove the nuts securing the air filter housing to the carburetor.

Carefully remove any choke levers and breather tubes.

Don't loose the gasket - you will need to reuse it.

Step 6: Install Stud Extenders and Gasket

Picture of Install Stud Extenders and Gasket

Screw on the stud extenders. Use a pair of pliers to snug them up by griping the smooth area between the threads and the carb.

Install the gasket included in your kit.

Step 7: Install Fuel Adapter and Air Cleaner Housing

Picture of Install Fuel Adapter and Air Cleaner Housing

Note the airflow orientation of the carburetor adapter. Dry fit the elbow and find the direction it should be pointing.

Remove elbow and cover threads in teflon tape or thread sealer.

**Ensure teflon tape does not extend past the last thread and get into the flow of the gas.**
**Note white Teflon tape as pictured is not appropriate for propane. All the white tape was removed and replaced with YELLOW once I realized my mistake.**

Slide the carburetor adapter over the stud extensions. Reinstall the air cleaner housing ensuring the gasket is between the housing and the carburetor adapter.

Install air cleaner and cover.

Clamp the fuel hose on the elbow. Reattach choke lever if it was removed.

Step 8: Install Zero Governer

Picture of Install Zero Governer

Install all fittings with teflon tape or thread sealer before attaching to the frame.

Hold the on demand regulator up to the frame and find two points of contact.

Mark, drill and bolt using the supplied bolts.

Please be careful - don't drill into the gas tank!

Step 9: Start and Load Set

Picture of Start and Load Set

Start the generator and get it to operating temperature on gasoline.

Turn the fuel valve petcock to the off position - and let the engine run all the fuel out of the carburetor and gas line.

Turn your set screw in all the way. As per my manual I had to turn it out five full turns.

Turn on the propane at the gas tank.

Press the prime button on the back of the on demand regulator for 1 second.

Start engine - adjust screw in for less fuel and out for more. Once you find the right mixture use the set nut to lock it in place.

**One full 20# (grill sized) propane tank has the same run time as about 5 gallons of gasoline.**

Also - if you want to get very scientific look up propane vaporization rates and how it relates to outside temperature, tank size and liquid fuel content. Very fascinating.

Step 10: Gasoline Operation

Picture of Gasoline Operation

To switch back to gas:

  • Stop engine completely.
  • Turn gas off at propane tank
  • Turn gasoline petcock valve to on.
  • Replace propane line attached to on demand regulator with the cap.
  • I also turn off the ball valve.

Step 11: Sourcing Your Kit

Several manufacturers make complete turn key kits for these conversions.

Mine came from US Carburetion -
- Note my kit was their old design, and was on clearance. Check out their new design!

Other companies include:

I would highly suggest checking eBay because many of these companies sell on there for less than their advertised price.

Step 12: Thoughts on Building Your Own

This was my first kit. I was planning on building my own until I ran across the clearance priced kit at US Carb.

The fittings, hose and low pressure regulator are easy to source at any hardware or home store.

The load set (fuel mixture) screw can be made with a tee, nut and a bolt that is longer than the tee - very simple.

Check Amazon and eBay for a "KN Propane Regulator" These run about $70 or less if you can find a used one.

The adapter is where you can get very creative. Several motors actually have spacers or plenum that could be easily modified to accept a propane inlet. I was considering designing one to be 3D printed out of ABS - or maybe even cutting up a hockey puck. If you build your own I'd love to see what you come up with.


wrenchit (author)2014-12-09

Nice write-up, I might suggest you specify the Yellow Spool Teflon tape as the regular Teflon that comes in the white spool will eventually break down from the gas and leak. Leaking propane around a running engine is a recipe for disaster. Its illegal to use white Teflon tape on gas appliances in Washington state. There are 5 different colors available.

As the PTFE tape industry evolved into more products they adopted a standardized color code.

WHITE- Single density tape to be used as a thread sealant on NPT (National Pipe Taper) threads which are equal to or less than 3/8".

YELLOW-Double density "Gas tape" suitable for NPT threads equal to or greater than 1/2" but not more than 2"

Red- Triple density tape suitable for NPT threads equal to or greater than 1/2" but not more than 2". (NOTE-The package is a red spool with a red cover ring and plainly labeled 'triple density", but the tape itself appears as a pale pink color).

GREEN TAPE- Listed as "OXY/MED tape"-certified oil free to be used on lines conveying oxygen and some specified medical gasses.

COPPER TAPE- Contains copper granules and is certified as a mechanical thread lubricant but is not certified as a thread sealant.

White and yellow are available at any hardware store.

More Cowbell (author)wrenchit2014-12-09

This is excellent information. I actually made the mistake of putting it together with white tape but have since replaced it with yellow and completely failed to mention it.

KD6 (author)2015-10-22

More Cowbell

I purchased the US Carb generic kit and installed in my 5kw Kawasaki. Your write-up is what got me thinking of converting my generator to run on Natural Gas. I went with the generic spud-in kit with the assurance from US Carb sales that I wouldn't have to permanently modify my existing carb to have it working. Well, that was not the case and I had to resort to fabricating an adaptor to go between my the air filter and the carburetor. Although I'm willing to forego the tri-fuel, but I'm not prepare to throw away a perfectly good carburetor. Mine, especially is harder to find and very expensive to replace.

My first attempt was a 1-1/4" steel shaft collar from princess auto ($3.99) that I drill the connecting bolt holes. The set screw hole made for a perfect location to solder in a 1/4" brass barb. It worked fairly well but I found with the 1-1/4" orifice, there was not enough venturi suction to engage the KN regulator, and to overcame this, I had to restrict the air flow through the air box by using a jar lid to cover the air spout.

My second attempt was a $1.00 hockey puck that I drill a 1" center hole and enlarge the gas inlet to a 3/8" to accept the full flow from the KN regulator. It's not perfect, but it does create the venture suction as the 1" hole is smaller than the carburetor's throat diameter creating an minor restriction and negative suction through the inlet gas line. The puck works especially well for those that do not have a lathe or any special milling machines. It's easy to work with and is rigid enough to be bolted/compressed and gasket is not required (bonus).

Overall, I was surprised at how simple the conversion is and how one can easily modify their generator to accept propane or natural gas. As for the tri-fuel adaptor, a simple steel shaft collar or hockey puck works just as well. Just make sure that the orifice diameter matches the smallest throat diameter of carburetor (i.e. at the carburetor's jets) and use the largest inlet spud tube as possible. This will require less negative venture suction to activate the KN regulator.

Thanks for the inspiration. I'll post an instructable on my two diy propane conversion adaptor. Cheers!!


juliobhi (author)2014-12-15

My Ford Mondeo works with CNG (compressed natural gas) the tank fills with 15 m3 of gas at 200bar!!! SEFI injection of GNC(gas natural comprimido)

espdp2 (author)juliobhi2014-12-18

Where do you live? I wish we could (easily) run CNG/GNC in our vehicles in America, but there are national fire codes that restrict the possession of a compressor at residential locations. I'd like to see that changed to be allowed, since we can use propane compressed to similar pressures, and natural gas is piped into lots of homes at low pressure. Given adequate commercial safety engineering, I don't see why we can't have CNG compressors at home.

juliobhi (author)espdp22015-09-12

home compressor? no! its a freaking crazy sh.. In Argentina we have a GNC stations like a ordinary gas station, and all the supplys and instalations of these equipament are regulated by the goverment.

appadee (author)2015-04-06

separate hydrogen and oxygen from water and use the hydrogen to run it.

brian.canterbury (author)2015-03-13

US Carb has the Motor Snorkel kits on sale for $97.47 this weekend. It's almost half price.

padakick (author)2015-02-12

For emergency power outages I use my car with a cheap autozone 400w inverter. I connect it to my house's wiring and only turn on the escential items.

bill.spaulding.16 (author)2015-02-07

You can refill tanks at tractor supply cheaper than swapping tanks and get 1 to 2 more gallons in your tank. Blue rhino and others only fill tanks about 2/3 full even

I completely agree! I have a local camper supply about 1/2 mile from my house. They fill tanks for much cheaper than you can swap a tank. I can typically fill up in the $8-$12 range depending on current propane prices.

jgilliamtx (author)2015-02-03

The only problem with city natural gas is that it has to be pumped sometimes to maintain line pressure. If you are without power there is a good chance that the pump stations in your area are without it also. Personally I will be converting for propane and have my supplier install an additional on demand regulator on the 250 gallon tank near the house.

More Cowbell (author)jgilliamtx2015-02-06

Very true - propane for me. Plus with Natural Gas a natural disaster could cause the city to turn off the gas supply to everyone.

SIRJAMES09 (author)2014-12-20

Sweet! :)

I never thought it to be this easy.....

Food for thought:

Those that live in a trailer/modular home park, often have to go to a trailer supply place to get parts for needed repairs(plumbing, propane, etc)....maybe some of the things one would need could be found at this kind of store....

providing you can not find it elsewhere,or find it cheaper elsewhere.

Very cool idea! :) TY for posting this.

PlanetaryGear (author)2014-12-16

If you’re planning to use Natural Gas have a chat with your local city or utility. We’re too far south for heating to be a life or death issue most of the year, and certainly during hurricane season which is the storm most likely to take out power here. So for safety the whole area gets it’s gas turned off once the mandatory evacuation is sounded. They may be significantly delayed in getting it turned back on depending on the policies of inspection and such they want to do when they get back so you might have have the gas when you most need it.

buskrat (author)2014-12-14

Very nice job two things were left out though coming from brigs&Stratton MST tech if you put this on your generator it WILL void all of your warranty. Propane is a dry type fuel that offers nearly zero amount of lubrication were gasoline will lubricate the upper cylinder propane will not.

Another side note a engine does not create vacuum! It creates a void and then atmospheric pressure fills the void and as for in the carburetor it doesn't suck the fuel out. The air move faster through the Venturi which creates a low pressure and atmospheric pressure pushes the fuel up through the carb from the float bowl this can no proved by plugging the atmospheric air vent on the carb. It will fun for a few seconds then die let it sit for a min and it will start for a few seconds then die because there is no atmospheric pressure pushing down on the fuel in the float bowl. So there is no vacuum happening just transfers from high pressure zones to low pressure zones.

I personally wouldn't switch a engines fuel source from what it was specifically designed to run on. Not all engines are designed the same. Not all the gaskets and materials are propane friendly or fuel friendly for example rubber gaskets and diaphragms are dried out by alcohol. Which is why most all small gasoline engines have warning that say no E85 ethanol destroys carbs unless they are built for it with ethanol friendly materials.

More Cowbell (author)buskrat2014-12-14

Thanks for the comments!

You are correct - I should have used the term suction when referring the the draw of the propane into the combustion chamber. The intake stroke of the piston creates a partial vacuum causing the air in the atmosphere and the slightly pressurized propane vapor to flow from an area of high pressure to low pressure.

You are also correct - changing to an alternative fuel will void the warranty if it was not originally equipped from the factory that way. However Briggs and Stratton engines power many standby home generators - which run on natural gas or propane. The manufacturer does post warnings about over heating and the potential to run at a lower horse power. However generators are designed to be used in a large open air space. I have yet to see any evidence of overheating on mine. In fact the company posts links to where you can buy an alternative fuel kit - a far cry from saying it will kill your engine. Engines designed to use leaded fuel (6 countries still use leaded gas) could have issues if they do not use hardened steel valve seats. That is what the tetraethyl lead was used for in the fuel (in addition to treating preignition).

I would beg to differ on the idea that propane will cause your engine to fail prematurely - in fact I see strong evident to the opposite. I've seen the insides of engines with 400,000 miles that look remarkably clean that were run on propane. Carbon is the culprit here. Carbon deposits will form on pistons, rings, valves and turn your oil black and causes it to break down - thus producing engine wear. Now I'm a little rusty on my chemistry but gasoline has between 4 and 12 carbon molecules (normally referred to as C4-C12) depending on the batch while propane only and always has 3 carbon molecules. Propane is also in the 104-112 octane rating (but it has less BTU's that gasoline). So it burns cleaner but has slightly less horse power than standard pump gas.

The US government considers propane a clean burning viable alternative fuel....but they also consider pizza a vegetable so take that with a grain of salt.

rusty0101 (author)More Cowbell2014-12-15

additionally the conversion doesn't involve the float bowl or valve at all. That is part of the carburetor that handles gasoline. This adapter actually feeds the propane into the carburetor with the air coming out of the air cleaner. As a result you could (not recommended) solder shut the float bowl valve without affecting the operation of the generator on propane.

I would advise that people check their generators before attempting this conversion for a different factor however. This solution is really only appropriate for 4-stroke engine generators. If you have one of the 2-stroke engine generators (often found on smaller generators, say 1kw) that requires that you mix oil in with the gas for the engine, don't do this conversion. For that matter go get a better generator if you are looking to do more than power up a tail-gate party or beach party.

LeeGoffmyown (author)2014-12-13

one of the most useful instructables ever

Thanks! I've been looking at those propane powered stand by generators - but they are just way too expensive.

adillbeck (author)2014-12-09

So, is this just install instructions on how to install a prebought US Carb kit?
We just bought a generator, and I've been looking at the US Carb website, but if one can be put together for less... Our generator is a bigger one, and it looks like we'd have to go with one of the more expensive kits.

Bowtie41 (author)adillbeck2014-12-11

I see what you mean.Good Lord,I didn't spend much more than that($320 I think) for my Genny new!

adillbeck (author)Bowtie412014-12-12

Depending on the size of the engine, you could use one of the class c kits, which aren't as much. Like $150 or so. Those go up to 12 HP I think... Our generator is 16hp, so we'd have to get one of the others, maybe. I really should call them and find out. It would be nice to not have to worry about driving out for gas in an ice storm.

More Cowbell (author)adillbeck2014-12-09

Yes, this is my install instructions of an off the shelf kit. This is the first of several I want to put together. I wanted the first to be a commercial version so I could have a baseline of success. I think showing the kit and the pieces could help someone design and build their own. I'd like to make a few carb adapters and put them on various stationary motors I have like my log splitter. I think I'll build a tank bracket to put the demand regulator on and then move that between engines. Typically I see the kit I have on engines smaller than 20hp. Also check out their eBay store as sometimes the prices are lower.

I'd love to see photos of your setup when it is done!

4maxthedog (author)2014-12-12

Very nicely done. I rely on these instructables because I cannot do everything. I have been looking for a generator and did not want to pay the price for a dual fuel. Thanks for your efforts.

More Cowbell (author)4maxthedog2014-12-12

Thanks! I too was not impressed with the brands of generators that offered gasoline and propane operation. Plus I found my generator used (one time from the same storm) for about 1/3 of the new price. Thanks for check out my build!

ar_caver (author)2014-12-09

Great job! I live in a rural area and have had to use my generator many times for extended power failures. The rings are tired, it burns oil and I have to find the time to re-ring it. I've always regreted that it was a single fuel unit and your instructable has inspired me to order a kit and change it to a dual fuel while re-building the engine.

How many hours of run time can you get on a twenty pound cylinder of propane?

More Cowbell (author)ar_caver2014-12-09

That is a great question that I should have addressed. I'll edit and fix that. One full 20# grill tank is about the same as 5 gallons of gasoline. I'd love to see photos of your build!

Bowtie41 (author)More Cowbell2014-12-11

Thanks for providing that info.I was always curious about run times.Right now,where I live,gas is about $2.39/gal here,and to swap out a Blue Rhino or similar is $18-19.99 so it's be higher than gas,but it would be nice to have an alternate fuel to fall back on.

More Cowbell (author)Bowtie412014-12-12

The Blue Rhino's run the same around here too. I've found the camper supply and hardware stores much cheaper. Ususally I get out for about $10 per 20# tank. Gasoline has been on a downward trend around here and I'll take it!

jorge.medin.1 (author)2014-12-10

Biogas could run , how much pressure is needed, because we have an amount of biogas

gronan1 (author)2014-12-09

Good going! I have A Miller welder/genny that I am going to convert to tri-fuel operation when the weather warms up. This will be A emergency unit for my rental house.

I bought another house as A primary residence 3 years ago and last summer I retired and just in case I decide to escape the cold and snow of Minnesota for A few weeks I used some of my vacation and sick leave money my employer gave me to have Home Depot install A NG genny. It was expensive but I can't get A genny out of storage and running when I am several hundred miles away. As it would cost me quite A bit to repair the plumbing if the house froze up I consider it cheap insurance and it will be A good sales point when I decide to move on.

ggarnier (author)2014-12-09

Garretson is another builder of propane carbs, don't know if they do a multi fuel product. Also, for CA residents: CARB may prohibit these unless they have been cleared for emissions.

gary.j.mcneish (author)2014-12-09

Anyone need one let me know I have them for sale.

chau8238 (author)2014-12-09

Just a suggestion for others, it'd be better to double nut the stud and then tight the stud with the nuts. Once it is tight, remove both nuts.

More Cowbell (author)chau82382014-12-09

Good call - that is how I install threaded studs with no smooth space. I did take the easy way out with the vice grips. Double nut and locktite is an excellent way to go.

rimar2000 (author)2014-12-08

This is a dream for me. I did the conversion on my own little 2.2 kw generator, it works in NG but WITHOUT LOAD. When I load it with more than 500 watts, it collapses.

Instead of an on demand regulator, I use an electric valve fed by the generator: when motor stops, the valve cuts the NG.

More Cowbell (author)rimar20002014-12-08
Gracias por su comentario - mi español no es tan bueno, así que usar un traductor también. Yo creo que hay uno de los tres problemas: 1. la mezcla de combustible es demasiado pobre en su generador, 2. Usted no tiene tubería de gas natural suficiente presión 3. Usted no tiene suficiente volumen de gas en el gasoducto de gas natural. Usted podría adjuntarlo a un tanque de propano para ver cómo funciona. Un litro de gas natural tiene más energía que un litro de propano. Así que si funciona con propano usted sabe que su problema es con el gasoducto de gas natural o de un regulador.
Espero a resolver su problema!
rimar2000 (author)More Cowbell2014-12-09

Thank you for your kind reply and your suggestions. Anyway, this happened over a year ago, and I removed from the device all aggregates. Really storage of gasoline is a problem, now I have nothing booking, if the power goes out'll have to run out and buy.
Gracias por tu amable respuesta y tus sugerencias. De todas maneras esto ocurrió hace más de un año, y ya le quité al aparato todos los agregados. Realmente el almacenamiento de la gasolina es un problema, actualmente no tengo nada de reserva, si se corta la luz tendré que correr a comprar.

Snidely70448 (author)2014-12-09

Nice job. We heat with propane and have a 250 gallon storage tank which gets no usage in the Summer, when we are most likely to have hurricanes, our usual source of power outages. We were without power for over 30 days after Katrina. In September. In Louisiana.

Budweiser143 (author)2014-12-08

Bummer. We here in Fl learned a LOT from Hurricane Andrew in 1992, and even more through out the years as weaker hurricanes passed through. Almost everyone has a generator with good supplies of fuel. As an electrician, generator hook up sure did provide me a lot of work through the years! I dont know about counties in the central and northern parts of the state, but in South Florida most grocery stores now have back up generators. In addition, several counties adopted ordinances years ago that any new gas station built MUST have a back up generator to run the pumps. I could go on about a lot of different things, but that's just a little about the generator side of things.

seamster (author)2014-12-08

Excellent project, and incredibly useful. Nicely done!

About This Instructable




Bio: I'm a computer engineer - but please don't judge me by that. I heat with wood, fix broken things and love camping with my ... More »
More by More Cowbell:Cheap Treated Clothesline - Our Solar Clothes Dryer!Campfire Funnel CakesWaterproof Underground PVC Cache
Add instructable to: