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Picture of 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.
 
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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

Picture of The carburetor
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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

Picture of 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

Picture of Remove the butterfly valve
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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

Picture of Remove idle and mixture screws/jets
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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.

Picture of Removing the jet hole plate cover.
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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

Picture of Primer bulb removal
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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

Picture of Venturi Jet removal
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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

Picture of Clean it up
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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

Picture of 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

Picture of Seal it up
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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

Picture of 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

Picture of New venturi tube
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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

Picture of 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

Picture of Put it all together
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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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kelms13 months ago
I like the idea of multiple fuels now only if it would run on methane
lksmith5 months ago

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.

Rainh2o (author)  lksmith5 months 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
ddudette1 year ago

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,http://gomowpropane.com/conversion-plans/. It's a good reference for your concerns about propane conversions.

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

neardood2 years ago
Wouldn't manually controlling the RPM of the generator cause it to make too many or too little volts? Not good for running any kind of sensitive equipment. In the video you can see the governor trying to adjust the revs to regulate the output
Depending on the generator design, it can be made to produce relatively constant output voltage with varying speed. The issue is that this is an AC generator, and uncontrolled variations in engine speed will produce variations in AC frequency. In North America we use 60 Hz power, although most appliances will probably work fine over a ±10% range (~ 55 Hz to 65 Hz), with reduced efficiency at either end. Don't expect to run something with a built-in clock that depends on line frequency for accuracy, though.

An AC generator should have a fully functioning governor to maintain proper output frequency.  This project describes an "open loop" system, i.e., no feedback whatsoever for maintaining engine speed under varying load and environmental changes.  For all the work involved in this Instructable, it is no better than sticking a propane hose into an unmodified carburetor inlet.
Rainh2o (author)  pcooper22 years ago
Yep..unregulated...but in a power outage when gasoline is not available this WILL work to charge batteries, run water pump, give you lights, let you take a shower, flush toilets (Im on a water well so we need electricity to run pump to get water) run a washing machine, maybe even warm up the house. Its better than nothing even unregulated. Actually sticking a 14 psi hose into the mouth of the carburetor would be easier, I just wanted to see what I could do with the old carb and give people an idea what was possible.

at least (this based on experence on a push mower) by sticking the hose into the carb throat you will still have speed and voltage regulaton by the throttle

plate moving thus controlling air/fuel mix, thus roughly speed and voltage adequatly enough, P.S. ever easer make it duel fuel by reinstalling original carb intact with butterfly on and connected and connecting the the hose fitting on top (crank case breather fitting) to the output of the needle valve, Plus you still have voltage regulaton, it might start hard due to gas an acculmlation of gas so start it quickly after turning on the gas. P.P.S. please please put on a proper air filter, or yout generator will not last very long. P.P.P.S i'm not tring to bash you, just tring to help you, I have spent my hours messing around running gas engines on propane. even have the same generator (the preivos version the flathead non-ohv)

Don't generators have a regulatory circuit that componsates for that? I have a diesel generator and as long as its running within about 1000 rpm of where it should it has 125v no problem, so low voltage shouldn't be an issue, maybe lack of amerage. The reason that generators need to run at a specific speed though is because of the Hertz I believe. They usually run at 3600rpm, which means 60 turns a second which would equate to 125v at 60hz. Rpms would affect the hz, but I don't think it would affect the power output to majorly.

The real problem I see is that all that has been worked on was the carb. Propane burns much dryer, and I have heard that propane engines need a modified lube system because they need more lube, otherwise they will wear out fast or even seize. Someone said once that they had a diesel tank on their propane power pickup because it injected a bit of diesel with the propane because the diesel helped lubricate or something. Said it used a very small amount of diesel and he only had to fill the diesel tank maybe once a year. That is just what I HEARD, it might be something to look into, it might be nothing at all.
In North America a generator engine will ideally run at some integral fraction of 3600 rpm. By having multiple poles on the generator it is possible to run the engine at 900 rpm (8 poles) or 1800 rpm (4 poles), which is more realistic for large-bore internal combustion engines than 3600 rpm.
Rainh2o (author)  Wesley6662 years ago
Im not sure why it would need a different lube system ina gasoline engine. Oil is not inside the combustion chamber when it fires with gas or propane. It is is you would burn through your oil. Thats what the rings are for, to scrape the oil off the walls. I dunno, thats the way I understand engines anyhow. Diesel, maybe, your talking way more compression and heat there and I can see the diesel acting like a lube because it is injected directly into the cylds. But a gas motor should not have oil in the cylds, you get smoke and fouled plugs otherwise.
Yes, your knowledge of engines is correct, that does not mean that everything burns the same way. Propane burns very dry compared to other fuels, and will cause significantly more wear on an engine. Some of our engines at work are propane powered but have no added lube system or use any other fuel mix and once a month we have to change the piston and cylinder walls. Usually when we change them, the top of the cylinder is pitted beyond belief, and the rings are either completely eaten away or seized to the piston, or welded, that would be a better word. The cylinder sleeves are usually heavily scarred as well. They are gasoline engines that have been converted to propane because it was problematic trying to get gasoline trucked in to sites, and they never had problems like that when they were run on gas, it was only after we changed them to propane did they require maintenance. Immediately after changed them to propane, they started failing catastrophically after about 3 months of use, one after another after another, usually pistons became so pitted they shattered while they ran and we figured out in a hurry that they needed maintenance sooner and needed it constantly.

So its not so much that the oil isn't doing it job, it is, but its in the bottom end, and the propane just wreaks havoc to the top end.

That is my experience with propane and engines that run on it. Apparently there is an injection system we could add to the engines so that they don't need so much attention, but the people at the top rather pay some guy an a55-load of money to implement his new safety system that really doesn't work! Haha!
Rainh2o (author)  Wesley6662 years ago
Everything I have looked up on running engines on propane since this part of the thread started insists you get longer engine life, due to no carbon build up and the fact that there is way less particulates in the propane so it burns real clean. I know fork lifts burn propane, does anyone have any experience in forklift maintenance and if so, are they just normal engines that have a converter for a carb?
rbodell Rainh2o2 years ago
A propane gas company will sell a propane carburetor for almost any gasoline engine built.

I have a diesel generator I run on waste motor oil. I do process the waste oil to get rid of moisture, filter it to 2 microns and bring the PH down to neutral. It has noticeable more power and burns cleaner than with diesel fuel. On diesel you have to de-carbon the piston every 700 hours on my engine. On waste oil it doesn't carbon up. I am in the process of trading it off for a diesel truck. Nothing like free fuel. I have some videos on youtube under rbodell.
Aren't forklifts usually electric or compressed air? And that is just what I have dealt with with propane engines. Usually yellows the piston and walls on ours as well.
Rainh2o (author)  neardood2 years ago
What sensitive equipment do you plan to run when the electricity is down for so long that there is no gasoline available and you need this to draw water with the water well, heat your house a bit and maybe charge some batteries and run some lights? Lights dont care, as long as the voltage and rpm are close, the motor on the pump wont care for short term and batteries dont care either.
sillywilly2 years ago
You know, all these instructions are nice and I appreciate the effort the author has gone to explain it but it's too complex and way too many steps. I see 3 things needed here 1) leave carb alone. Instead, cut a small hole in the right-angle rubber elbow on side of carb (EGR). Use high-temp silicone to glue new nipple into hole. After silicone sets fasten LP hose to the nipple. LP can now go straight into the venturi of carb. 2) manual regulation of LP is needed for fine adjustment. 3) Let governor regulate airflow automaticaly using it's tie-in to the butterfly valve (throttle). Thats it! Credit to author "auxpowerunit" on youtube who shows how it's done. Here is the video ID GfPmtzYh-XE
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could not have said it better myself, short of getting a kn demand regulator and with the throttel butterfly will regulate fuel mixture and speed based on engine vacumm

Rainh2o (author)  sillywilly2 years ago
what's the fun in that? Like I've said before so many times in the comments, I did this to just see if it would work. even an easier way to do it would be to still a hole in the air breather Cover and just stuff the hose hosein there. a 3min operation.
dunklesubel2 years ago
You should NOT use teflon tape on compression fittings, especially if you are running flammable liquid / gas through the lines.
Corynick, that is why I mentioned to not use it on compression fittings. I mention flammable liquid / gas lines again because of the consequences involved, not because that makes the compression fittings different. From my statement, I clearly include all compression fittings in my "do not use teflon" statement.

Pcooper2. Yes, as corynick mentioned, thread sealant is use on fitted (threaded) pipe, but not compression fittings, and you would need to use the proper thread sealant tape or paste, or whatever based on the application.

The reason that you do not use thread sealant on compression fittings is that the threads do not seal, it is the cone-shaped mating surfaces that form the mechanical seal as the two pieces are threaded together. By adding teflon tape or other thread sealing compound into the threads, you may prevent the two cone-shaped brass surfaces from contacting each other with sufficient force to form a mechanical seal.

Threaded pipe, though tapered, is not a finely machined deform-able mating surface, and does not form a sufficient mechanical seal without the addition of teflon tape, or liquid thread sealant.
The flammable gas has nothing to do with it, thread sealant is always used on fitted pipes regardless of flammable gasses or not. The problem is using teflon on compression fittings. It isn't needed or wanted there.
Why would heavy duty Teflon tape be sold in most hardware stores, specifically for use on natural gas lines? It is usually yellow in color and much thicker than the white tape used for water lines, but Teflon nonetheless. Teflon is essentially inert in the presence of all hydrocarbons used as engine fuels or heating fuels.

The only issue I would have is use of any kind of tape, putty or sealer on compression fittings. Compression fittings are supposed to be liquid- or gas-tight on their own; if they aren't, they need to be fixed or replaced.
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Rainh2o (author)  pcooper22 years ago
I agree pcooper2.
Rainh2o (author)  dunklesubel2 years ago
Why not?
beijing20134 years ago
i was just wondering about that safety shutoff valve... if you had an engine with an alternator on it, could you use that to power a solenoid valve, so the minute the engine stops turning, the propane supply would turn off, and you could have a manual override button for starting. anyone got any ideas on this?
sounds like a great idea to me, on any generator you could just run it off of the wall voltage output too. i cant find any cheap solenoid valves though.
could use an lpg boiler gas valve if you could find one at the tip
The 4th Doctor, during a power outage there is no "wall voltage". The system needs to be self-contained for safety.
Rainh2o (author)  pcooper22 years ago
I think he means run it off the wall voltage output on the generator.
quick search on amazon brings up a few for about $15. will you be converting a generator?
rimar20002 years ago
Your work is far better than mine, Rainh2o.

How many hours lasts that propane container running? I tried to use natural gas, but I can't apply charge to generator.
londobali2 years ago
Great 'ible, Rainh2o!
Thanks for sharing..

As for safety shut off, Rimar2000 did a pretty neat trick with his conversion, and was cheap too..
he used a solenoid valve that was for a washing machine (i think??), just need to be sure it's a normally-closed type.
Oh wait, i thing he ended up with having to modify the solenoid to allow a higher flow, or something..

Did you compare which one runs cheaper: the propane or the gasoline?

Anyway, thanks for sharing.. If i knew it was this easy (and cheap) I would have done it when i lived in Borneo where they have power blackouts every day for three hours!!
Cheers!
Rainh2o (author) 2 years ago
This is what I have found so far about running engines on propane:

-Power output is slightly reduced, so there is less stress.

-Effective octane is very high, so the engine never suffers from detonation related stress.

-There is no liquid gasoline to wash the lubricating oil from the cylinder walls, so ring and cylinder wear is minimal.

-Combustion is usually very complete, so there is little carbon left in the cylinder, which is lightly abrasive.

-The complete combustion means that there is very little acid etc in the blowby, so the oil tends not to break down or otherwise get nasty.
dereal3 years ago
Hey!!! Great Job! But which site can I get the pdf manual or guide using the gas conversion kit?---Some should forward it to my mail:derealtechnologies@gmail.com
dereal3 years ago
Hey!!! Great Job! But which site can I get/read the pdf manual or guide using the gas conversion kit?
To end the backfire/explosion worries, just go to a local welding shop and buy a flame arrestor, a simple device used on cutting torches to prevent flame burning back up a torch hose and into the tank. The one for the Acetylene tank would likely work well, and the guys at the welding shop can aid you with selecting the right fittings to make the arrestor fit into your rig.
mpikas5 years ago
I don't get it, why go to all this effort?  You could just drill and tap a hole someplace in the casting and leave the carb functional, maybe put a shutoff valve in he gas line. 

That way you have a setup that can be used for either, shut off the gas and run it on propane, or close the propane valve an run it on gas...
Rainh2o (author)  mpikas5 years ago
first I didn't want to drill a hole in my airbreather.  Second I had the old carb laying  around and it was trash and just  wanted to see what it would take to make it work like this.  No other reason.
mpikas Rainh2o5 years ago
Yea, i get that you had the junk carb, but my point is that you didn't need to even mess with that.

A MUCH better way of doing this is to find an open spot in the carburetor casting, intake casting, or maybe make a spacer 3/8-1/2" thick using the carb gasket as a pattern (could be out of anything, aluminum would be best, but lots of plastics will work, as will any decent wood (soak it in "aircraft dope" or model airplane stuff from SIG, thin epoxy or a dozen other things to seal it), then drill a hole in the side of it and tap it for an 1/8" NPT thread.  Then take a brass hose nipple with a 1/8" NPT thread, solder, epoxy (JB weld...) or braze a short length of tube into the opening on the threaded end, and then crush the end so it acts to spray the propane into the throttle bore when threaded into the hole in the spacer.  The crushed end will give it some velocity and turbulence so it mixes better and you shouldn't have to worry as much about throttling the airflow in, it should run well over a broader range of mixtures.

Hook up your regulator + needle valve to the hose barb with a length of hose making it convenient and go for it.

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