Introduction: Multi-Fuel Generator - Gas Propane NG

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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

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

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

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

Remove the air filter cover and air filter.

Step 5: 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

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

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

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

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

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.

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