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    DIY Generator Conversion

    I have an older generator with a Briggs and Stratton 10 hp engine. We have only needed to use it a few times but the issue with gasoline fueled generators is when things go sideways gasoline becomes difficult to find. So I decided to convert my existing gen set to propane or natural gas. The good thing about propane is it can be stored for long periods without it deteriorating like gasoline. Natural gas is the same but during a power outage it is seldom interrupted.

    There are lots of kits available to do the conversions usually costing between $150 and $200. I chose to save a few bucks and source the parts needed and do a DIY conversion. Basic parts needed are a regulator, some way to regulate the fuel flow to the engine and some way to introduce the gas to the engine intake.

    The regulator is called a demand regulator. There must be a slight vacuum on the outlet side to get it to open and flow gas. This is a safety device so that if the generator stops the gas stops also. The regulators commonly used in this application are Garrison. I bought this one from Century fuels.

    The Model KN is a secondary, automatic zero regulator designed for maximum sensitivity and simple, trouble free operation.


    I made the gas flow device using a 3/8" brass pipe tee. It has a 3/8" X 1/8" pipe bushing in one side with the bushing drilled and tapped for 1/2-20 threads. A 1/2-20 bolt is used to regulate the flow. There is a jam nut on the bolt to keep it in place when the gen is running. This is where you tune the air/gas mixture to get the best performance. Switching from propane to natural gas will require an adjustment. A ball valve or globe valve would probably work as well.

    To inject the gas into the engine intake I made a 3/4" thick donut that fits between the carb and the air filter. There is a 1/8" pipe thread in the side with a 1/8" NPT x 3/8" hose adapter. The bore is slightly smaller than the carb bore so there is some pressure drop to operate the regulator. The carb studs need to be extended to account for the thickness of the donut. On my Briggs engine the studs are 1/4-20 thread so all thread works. Had it been metric I would be looking for some long metric bolts.

    The regulator is mounted to the gen frame and needs to be mounted vertically. The regulator is supplied with two red plastic plugs that vent the atmospheric side of the diaphragm. Make sure you remove these plugs. Probably not a bad idea to re-install the plugs for storage. Dirt daubers love places like this to nest and the regulator does not work unless vented. I added a voltage and frequency meter from Amazon to complete the conversion.

    Then the question becomes did I save any money over ordering a kit. the confirmed answer is maybe. The regulator was $70 delivered. There are probably another $20 in pipe fittings and hose to get to the materials in the kits. In addition to the materials in the kits I set up my gas supply with quick connects so that was additional. I bought a 12 ft propane hose with quick connects from Amazon that was $40.

    Happy to answer any questions.
    Attached Files

    #2
    that is cool. You way more talented than me on small engines!

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      #3
      Originally posted by Killer View Post
      You way more talented than me on small engines!
      Not true. I was just on here a few days ago looking for help with another small engine. Watch lots of YouTube.

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        #4
        Good stuff! I read your post before scrolling down to the pics and you described the setup perfectly. Great work

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          #5
          Thanks. The piece that almost stumped me was the red plugs in the regulator. The regulator comes with no instructions so you are on your own. I had tried several different things but just could not get it to take any fuel. Removing the red plugs was one of those revelations that came to me in the middle of the night. The red plugs keep one side of the regulator isolated from atmospheric pressure so the diaphragm is unable to move with the vacuum in the engine intake.

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            #6
            Very nice job. I went with the US carburetor kit for around $180.

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              #7
              I like it! i picked up a kit for 115.00 off ebay for mine. I already had a duel fuel Gen so i just removed the propane injection hose and ran the NG hose to that nozzle down stream of the carb.

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                #8
                It was a lot simpler and cheaper for my Harbor Freight Predator 8750. I did some research and ended up ordering this conversion dual fuel carb kit off Amazon for $33. Took about an hour to install since I had to do some modifications and a slight work around.
                She fires right up every time and we are good to go.



                Even shot a short video of the first start up on LP.

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                  #9
                  initially I thought I could use the regulator from one of the Honda carbs instead of the Garrison regulator. But when I hooked it up the regulator would not shutoff when the engine stopped. It was bleeding gas through continually. Maybe I got a defective unit but it was too late to return it. I have a Honda engine on my pressure washer so I have a spare carb for it now.

                  The Honda engines seem much easier to adapt to dual fuel than others. Almost all of the gen sets I look at use Honda clone engines.

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                    #10
                    Nice job indeed. And if you have a large propane tank on the premises, you will have uninterrupted power for a long period w/o having to worry about refueling. A couple of things to consider with propane/NG is duty cycle and power loss. I think the typical rule of thumb is ~10% less power when converting to propane/ng over gasoline? And I'm not sure the duty cycle of most small generators, but the process of stopping to refuel provides some downtime even if it is minimal.

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                      #11
                      Wowwwwww absolutely awesome

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                        #12
                        I just ordered a PTO generator for my tractor for this very fact, gas getting old just sitting there. Now I may have to do this fix to my rolling generator, I could have saved myself $1500.

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                          #13
                          Nice, Got me to thinking.

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                            #14
                            Originally posted by RattlesnakeDan View Post
                            I just ordered a PTO generator for my tractor for this very fact, gas getting old just sitting there. Now I may have to do this fix to my rolling generator, I could have saved myself $1500.
                            If I were to do another generator i would buy consider buying the kit. I have a machine shop so i made the intake donut and the fuel valve. If I put a value on my time i did-not save any money.

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