Propane Converted ATV




Hello all, this is going to be a somewhat simple instructables. So here is some background information on the build, it started when a few years back we had a Polaris 350 Trailboss, and the engine finally gave out after many years of enjoyment and after that we just let it sit unitl we finally remembered we had an old Honda 240cc cement mixer engine with a gear reduction already on it, so it sounded like the perfect fit for it. So without going much more into the background here is the build. 

 Just to be clear I and the people involved in this took extra care while handling the propane, and we are not responsible for any damage caused to yourself or any property that you, (or your neighbors) may own. So please only attempt this if you know what your doing, and have sufficient common sense to know what you should and shouldn't do.

Also I am very sorry for the video quality thats all I could upload on to Instructables.

Here is a link to the youtube video it is of much better quality.
Here also is an older video of it with details.

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Step 1: Getting Started

So first off your going to need a somewhat good mechanical background, and be familliar with som basic tools. Here is the main bulk of tools used,

1) A full Metric and Imperical wrench set, sockets also.
2) Some angle Iron. (If your doing a complete rebuild)
3) Screwdrivers, Allen wrenches(Hex keys)
4) A welder, (again only if doing a full rebuild)
5) A reciprocating saw, a drill, amd various other power tools. (again for a full rebuild)
6) Other basic tools you will know waht you need once you get into it.

As for the ATV, prefferable one that doesn't run, or it is old and you don' t care about it's safety, do not use it if it has a 2-stroke requiring pre mixed fuel, only use this conversion on 4-stroke or 2-stroke oil injected engines.

For the propane system we used a weed burner with an adjustable valve to regulate the gas.  

Step 2: Propane Conversion

This is the main step in the entire process, to start you need to find a suitable place to mount the propane injector, which is just a brass fitting we found. Basically you want it where it can mix directly with the flow of air but not have to pass through a filter, this is hard on new engines but hopefully you won't be converting a new engine. Although you could try and inject it straight into the air manifold and let it go through the filter. But anyway it works best when it is directly injected into the carb. Also this should only be performed on a 4-stroke engine or if your 2-stroke has direct oil injection, some 2-strokes require a mixed fuel and this will not work with the propane beacuse the propane has no lubricating properties like the mixed fuel and oil does.

Step 3: The Engine

This is just a basic walkthrough of the engine, everyone trying this will most likely have a different engine, but basically we used some angle iron and the pre-existing engine mounts to hold it. You want it to be secured tightly and mot have any wiggle room, this may require making extra mounting brackets with angle iron. Also make sure you can keep an air fileter on the engine ours required some modifying. As for the exhaust we used an old lawnmower exhaust that we cut and modified to fit the engine mounting plate. The exhaust was mounted upside down because of an odd curve in the main pipe, but the tip is supposed to face down but now it faced up so we needed a deflector and turned to the next cheapest thing, a monster energy can and JB Weld. We also used the riginal handle bars to control the throttle on the engine but you must also regulate the gas valve to prevent it from stalling.

Step 4: Drive System

As for the drive system everything on the original polaris was removed because it could no longer be used, so insted we mounted a jackshaft to the original mounting plate for the transmission. Once that is done a sprocket is needed to to tranfer the power from the jackshaft to the main drive sprocket. If you look at the picture it its a relatively simple setup for the drive system. A sprocket and centrifugal clutch would work better. But ours having a gear reduction we didn't think it would turn up enough speed to activate the clutch and we didn't build it for speed either. Having the pulley sizes like we have made an even larger gear reduction giving us a lot of pulling power but the belt doesn't have the frivtion needed to pull a lot of weight so it's kinda difficult to get it moving on an incline. The tension pulley is activated using a hand grip mounted to a handle.

Step 5: Drive System Cont.

This part deals manily with the jackshaft and back, to start the shaft must be positioned level and squared to the frame otherwise it will put extra stress on the bearings. the sprocket used should be very small compared to the rear drive sprocket the rear one was like a 40 toothe so the jackshaft one is an 18 tooth a lower tooth count will give you a greater reduction in gearing. After that point the mounting is pretty much self explanatory. Just line it all up and your good to go, oh also for the chain use a heavy chain such as #50 or 520, and for breaking the chain it is best to grind down the pin so it is level and then use the breaker to punch it out otherwise it could break your breaker.  Also if you don't have a chain breaker you could try and take it to a local motorcycle or ATV store and they might be able to do it for you just be sure to measure it correctly for them to cut.

Step 6: Electronics

As for electronics its up to you, we used the original key and handlebar switches for all the stuff. When we were building it we simply used a radioshack project enclosure and mounted the key to the side and the extra switches to the top, then mounted it sideways to the original gear shift lever on the Polaris. Make sure you use heavy wire throughout the vehicle so they don't short out. If you engine has a charging system then it is best t ouse that for the batteries otherwise we used a solar pannel to charge the battery during day riding and then just use the battery conservatively at night. As for the light they are old fog lights we had laying around and one set is hooked to the hadnle bar switch and the other is connected to a switch on the radioshack box.

Step 7: Aesthetics

As for the body it just looked to naked so we made up some plywood sections and tacked sheet metal to them and painted it black, the seat is the original seat but it had to be cut to clear the exhaust and it had a rip in it so we recovered it with an old leather chair we had laying around. The main body is up to you to do what you want with it.

Step 8: The Finish.

Now that you have your new creation it is time to enjoy it. Make sure everything is mounted up securely and if you choose to use a small propane tank make sure it is mounted good. Then if you can't disengage the drive system or your unsure about it block it up on a jack for starting. On our engine to start it you open thw gas valve until you can hear just a small amount going into the engine and then hold wide open throttle on the engine not the gas and crank it as soon as it starts then release the throttle and possibly adjust it to prevent stalling. As you increase the throttle you need to increase the gas flow to prevent stalling but not to much gas, it will take about a week to get it down and keep it running smoothly all the time. After that your pretty much done you can then add whatever else you want to it.

Step 9: Complaint Department

Ok so if you want to see anything else just let me know here or if you have any questions here's the place, also if there is anything you think can be improved or is wrong please don't hesitate to tell me, or if you just want to complain feel free to also. Hope you all enjoyed it all.

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    15 Discussions


    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. :)


    8 years ago on Introduction

    I agree, very neat conversion. Thanks for sharing.

    Would it be easier or more difficult to convert a 4 stroke fuel injected motor vs a carburated one? I have a fuel injected scooter that I'd like to try to convert.

    3 replies

    Reply 8 years ago on Introduction

    I cant tell you 100% for sure, my set up is all custom. most likely a carburated would be easier. my set up is i plugged the fuel lines on the carburator. and then right at the front of the carburator flapo put a small pipe that directs propane into the carburator, as the carburator is oppened you must in crease propane flow manually to provide adequate fuel to air ratio, basically doing the job of a carburator foat bowl manually since the floatcannot control propane it would freeze or simply blow upwards having no effect, i used a small valve off of a propane weed burner. also keep in mind that propane is equivalent to 100 octane gasoline. your engine will have considerably more power and possibly higher running temperatures, most engines can be done if observation is keeps strick on the lubricating side of things propane provides no upper cylinder and valve lubrication, so dependng on your engines lube system it may not be a good idea


    Reply 8 years ago on Introduction

    I'm really not sure about the fuel injected engines because I haven't been able to get one to experiment with but you might be able to hook the propane to the fuel line with a pressure regulator and reducer, then you might be able to let the engine ECU still controll the fuel flow with the injectors but I don't know if it would cause vapor lock because the injectors are made for liquids. But if the propane is pressurized then it shouldn't matter, you would also want to disconnect the fuel pump if there is one, to prevent it from overheating. But if that doesn't work then there should be an intake for the engine, possibly right on the cylinder, and you could rig a nozzle there just like a carburated engine, just check to make sure there is a backfire arrestor on the intake, and then its the same process used in this instructable.


    Reply 8 years ago on Introduction


    thanks, I'll give this a try. But I probably won't do this to my good scooter. I'll see if I can get an old junker similar to it and experiment on that one.

    That would be neat but regulating the gas levels could be a pain especially on a moped, you maybe could look for a carburator that is made for propane, that would be better as it would regualte the gas and the throttle body valve at the same time. But if you do it I'd love to see it posted.

    i was actually thinking of using a regulator from a small porpane camp stove, along with the small disposable bottles of propane you can get at wal-mart

    The valve would work but you also have to increase the gas flow as you go faster. So it would be like some old motorcycles where you had to open the throttle with one grip and adjust the timing with the orbs. Also the disposable cans can get expensive you should look into a small 1 gallon tank you can refill or make an adapter to refill the small disposable tanks from a larger tank.


    8 years ago on Introduction

    Would be a cool idea untill you burn out your piston .propane burns to hot to make this mod.

    1 reply

    Reply 8 years ago on Introduction

    It will run on a small tank for about 8 hours. The tank in there is either a 1 gallon or a 5 gallon I can't remember it right now.


    8 years ago on Introduction

    Excellent work. It reminds me an adaptation that my father did in the 60's, over a tractor that used an elusive fuel, it finally worked with a bottle of propane / butane.

    I recently bought an electric generator of 220 V, 2.2 KW, which runs on gasoline, and will be likely adapted to run on natural gas (methane) as this is much cheaper. This instructable will be a very good guide!


    8 years ago on Step 4

    This is really neat! I wish I had one so bad!