Homemade Automatic Choke for Generator.

JBish130JBish130 Registered Users Posts: 7 ✭✭

I've been working at this off and on for about a year, but finally hit success.  The goal was to install an automatic choke on my 7.5Kw generator from Harbor Freight.  (This is basically a clone of the 7.5Kw Generac I have.)  If I could get the automatic choke to work, then I could wire the switch to the AGS panel for my Xantrex 6048 off grid system.

I tried using air pressure from the blower shroud to open the choke (which almost worked), but ended up using a $3.50 solenoid from China and a little scrap metal.

When I first put this together, I wired it to switches inside our cabin.  I wanted to be able to test it and have it prove itself before I ordered the Auto Gen Start controller.  It worked good, we would push a button to start the generator and flip a switch to shut it off.

With the Auto Gen Start right now, my generator starts up automatically as needed based on the charge of the batteries.  I don't use the "quiet time" feature and don't mind hearing the generator start up.  Instead I take deep satisfaction of how well this system is working for me.

There are a number of steps that I took to do this, nothing too complex.  The nice thing I did take into consideration, because I have two different yet essentially the exact same versions of these generators mentioned above, I made it so that it could easily be switched from one generator to another in the future as I replace worn out generators.  I use the Harbor Freight generator as my primary generator, it has about 2,000 hours on it.  My secondary generator is the Generac, which has about 3,000 hours on it.  I will outfit both of these with the automatic choke, so in case the primary generator fails for whatever reason, I can switch a plug from one generator to the next and put that one into immediate service.  That's my plan B.

The first step was to modify the plastic choke lever itself.  It has a "locking" feature where it "snap" into either full choke or wide open.  Close inspection, though it's really hard to see, shows that the bottom of the plastic lever is formed in a way as to "bind" in those extreme positions.  I heated the flat of a screwdriver and slowly reduced the shape of the choke lever until it would move freely from full choke to wide open with no restriction or binding.

Once I had the air cleaner off of my generator, which I had to do just to get a good view of the carburetor, it occurred to me that I happened to have an extra carburetor for these generators around.  Anyone else could use their existing carburetor, but would have to remove it from the generator.  I took a couple of long toggle bolts and bolted the air cleaner to the carburetor so that I could have them together as they would be on the machine while holding the assembly in my hands to get a good look at it.  The course of action was quickly obvious to me while seeing the carburetor in this manner.  I would cut a piece of flat stock that would rivet onto the air cleaner and extend level most of the length of the carburetor.  From there I would take a shorter piece of that same flat stock, and put a 90º bend in it.  Once the first piece was attached to the air cleaner, I lined up the angle piece and clamped it into position for drilling and rivets.

I had made a stencil from the bottom of my solenoid and punched through the centers for two mounting screws.  I placed that upside down on the angled metal and aimed it at the metal pin extending from the choke lever that moves the butterfly for the choke.  Once drilled and mounted, I placed the choke in the full open position and measured from the pin to where the pin goes on the solenoid.  This measurement will depend on how you position the metal supports.  I marked and drilled two holes in a piece of scrap tin the distance needed for those two pins, and snipped out the tin.  This will act as the pull rod for the choke.

The electrical connections for this solenoid are 12v.  I wanted the choke to be pulled on full when the engine is cranking, so I connected one lead to the starter wire at the starter solenoid and the other wire to ground.  I activated the solenoid and found that it closed the choke completely.  I was concerned about this because the solenoid I used only had a 5/16" total range for working the choke.

The electrical connections to the switch were simple enough.  The switch is the "rocker type" with an OFF, RUN, and START position where the START position is spring loaded.  I leave the generator in the "RUN" position at its switch for remote operation.  There is a reason for this.  If you were to check the back of the switch, which requires opening the panel for access, you would find that the switch as six connections on the back side.  Two sets of three contacts.  If you were to check them for continuity, you would find that the "Power In" contacts on the switch are the two center contacts.  When you push the switch to the bottom position (OFF) those center contacts will connect to the top contacts (it's counter-intuitive unless you think about it).  When the switch is pushed and held in the upper (START) position, the two center contacts make connection to the two bottom contacts.

I soldered three lead wire to the three left (viewing from the back) contacts, ran it out through a hole I drilled in the back, and soldered a three pin plug I happened to have laying around.  If I were to cross the center pin on that male plug to the start side of another pin, the starter motor will get power, the choke will pull shut and the engine will crank over and start, usually within about one half second.  As soon as the starter isn't being cranked anymore, the choke will let off and go to the wide open position because of the spring on the solenoid.  When I cross the center pin with the other pin the generator will shut down.

That is the extent of the needed modification to the generator.  So long as I solder the cable I made up to the back of the switch, use my existing air cleaner body, pull rod, and modified choke lever (which is held in place with one screw), the system will quickly swap over to any other clone version of my generator.  Again, this system is working absolutely perfectly for me.

I'm not responsible for someone messing up their generator.  I'm not suggesting anyone do this.  I'm just saying that this is what I did and it works very well for me.  I can't express how very pleased I am with the results of this modification and the Xantrex AGS controller!


  • JBish130JBish130 Registered Users Posts: 7 ✭✭

    So my photographs are all in here perfectly backwards.  For a normal progression, start with the bottom photo in the first message and work your way up from there, come to the bottom in this message and go up again.  Sorry about that, I'm not real proficient with this message forum.

    I neglected to photograph my snipped out tin pull rod, because it was getting dark by the time I got it cut and installed, and I had to get the generator back together because his unit was the one "in service" at that time.

    I'm working on a YouTube video of this project, but that's taking longer than I expected, and I am sure that there are a lot of people out there who are interested in this project.

    While I was typing this up (and this took awhile) my generator had fired up, charged my battery bank, and shut down for me without any action on my part.  I keep tabs on the oil level and changes and keep an eye on how much fuel is in the tank.

    We have been living in this small cabin (we haven't got the house built yet) since 2013 going on our fifth winter here in the mountains of western Maine.  We do have telephone and thus internet here.  The power poles stop a mile down the road from us.  We are powered by a hybrid solar generator system that works out well enough for us using 4 panels, and 4 batteries.  While there is a little mix and match with a couple Midnight Solar components, our system is mostly all Xantrex.  We are using the 6048 inverter/charger.  All of our lighting is LED, however we pumping water from a shallow well with a regular 120/240v shallow well pump, we use an electric deep freeze (our refrigerator is propane) and we switched over from a wood burner to a pellet stove in the fall of 2016 (electronic ignition, all the blowers, etc.)

    When we build our house, hopefully next summer, we will move this electric system into that house while adding some panels and going from one bank of batteries up to three or four for more reserve storage capacity.

    I've been walking out and starting the generator for some years now.  Having the switches installed inside the cabin was a huge advancement just so that I wouldn't have to walk outside anymore to start the generator.  With this system, we can be gone for a week and know that our food will stay frozen and the batteries will always be charged.  My wife LOVES this new system.  It really does work perfectly for us.

    I will be more than happy to discuss this system with anyone who might be interested.  The benefits to ourselves is huge.  I'm running a $536 generator from Harbor Freight that was never designed to operate like this, which for me is a lot better than spending $6,300 on a Honda 7Kw generator that comes with these same features right out of the box.  It isn't just that I saved over $5,700 by doing this, I will save that much again every time I have to replace a generator.  With a system such as ours, it should be noted that the generator (being a mechanical device) is the only thing that "wears out."  I consider it a "Consumable" type of component for our system.  I imagine the cost is why there are so many people trying to convert regular generators over to two-wire, which is fairly easy, the trick is in the automatic choke for those 'new' two-wire generators.  Also, the main part of my choke is the solenoid, which at $3.50 each, I can keep some in stock if I'm concerned about how long they might hold up (and I'm not really concerned, I expect a long life from them).  It's hard to imagine any solution that comes in at a lower cost, too.

  • mcgivormcgivor Registered Users Posts: 1,280 ✭✭✭✭
    Nice to see your achievement, keep an eye on the pop rivets, vibration may, over time, cause loosening, using stainless may be better. Is there any provision to stop trying to start if there was no fuel for example, not difficult to do with a timer and a relay, another project perhaps, with AGS and nobody home it would be good to have as many safeguards as possible, low fuel cutoff is another idea. 
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • JBish130JBish130 Registered Users Posts: 7 ✭✭

    I'm hoping the pop rivets hold up as well.  If needed I could braze the metal supports into position.  When I was putting this together, I had already been conditioned to failure on the project.  I'm not an engineer and half the time I'm working by eye-ball, which is why the photo's show how I lined things up.  This is also why nothing was initially installed in some permanent manner.  Once it worked, even when we were still using the switches (which can be still used if you know you're going to have a high demand for the pump or microwave, etc.) I expected something to fail as well as some debugging for at least the first week or two.  While at a month this system hasn't been tested long-term, it is working very well for us.  I don't see any point where failure is imminent.

    Whenever I put something together, I try to do it in a temporary manner where I can always back up to where everything works like it did before I modified it.  Sort of like backing up your computer before you make some big change so you can get back to your starting point.

    I am thinking of getting and using a 30 gallon drum as an auxiliary fuel tank for the winter and setting it closer to the drive where we clear snow.  Last winter we topped off at 6' of snow in the yard and fields.  Here is a little video of our snow:  https://www.youtube.com/watch?v=m53v22fKcv8&t=4s   What you can't see in the film is that the "ground" that we are cleared down to is snow and ice pack that is two feet deep, so the snow is that much deeper than it looks.  Also, while we "peaked" at 6', we average 5-5.5' for most of the winter as the weight of the snow settles constantly.  The "path" I'm filming from at the end is the path to the "generator annex" on the side of our lawn shed.

    At some point I will add the internet connectivity to my system, so that if we are away I can pull our system up on the web to keep tabs on it.  Right now, I'm pretty confident that this system is going to be fairly trouble free.

    For those trying to make a system like this work, don't give up.  It can be done.

  • westbranchwestbranch Solar Expert Posts: 4,860 ✭✭✭✭
    +1 for ingenuity...
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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