Homemade Automatic Choke for Generator.

JBish130JBish130 Registered Users Posts: 8 ✭✭
edited October 2016 in Solar Beginners Corner #1
Hi, I have a small hybrid solar power system up here in Maine, we are entirely off grid as the power company doesn't have service along our section of the road. We use a Xantrex 6048 inverter, 4 Trojan AGM 8D batteries, a Xantrex Solar Charge Controller, and 4 315w Solar World panels and 7000-7500w generators.

Since our system is currently as small as it is, we always bump up the batteries with the generator at night before we go to bed. This assures us that we won't wake up to the beeping warning us to low battery power first thing in the morning. My current goal is to install an automatic generator start/stop control for our system so that I don't have to walk out and physically start the generator. While this isn't a problem (either generator is electric start), driving rain or blizzard conditions makes it less than the perfect situation.

For us, the problem of making our generators automatic start is the lack of an automatic choke. Many have arrived at this exact same situation, you want to make the system automatic but lack the proper generator to do so. We are currently using a Generac 7,500w unit, and an identical (except for paint and brand) Predator 7,000w unit from Harbor Freight. Except for slight cosmetic differences, these are the exact same units.

Yesterday I accomplished the homemade automatic choke for our generators and it cost next to nothing. I thought others might be interested in how I did this. I decided to use air pressure from the blower to operate the automatic choke. There is a rubber plug on the front of the cowling that gives access to the blower. I fit a 1/2" brass angle into that opening and secured it into place. From there, I ran a plastic 1/2" pipe down under the engine to the rear of the unit where I used a couple of 45º angles and a little more pipe to direct that air towards the choke lever. I had to modify the choke to remove the "locks" that hold the coke in the open and closed positions. For this, I removed the carburetor and smoothed down the plastic part that mounts on top of the choke shaft. This allows the choke to flop around open and closed with no restriction. I removed the choke lever and added a wire attached to a small lightweight spring to gently pull the choke into the closed position. Then I cut out a piece of plastic which I used plastic wire-ties and Gorilla Glue to attach to that lever as a wind vane. As soon as the engine starts, the air blowing from the pipe aimed at the choke lever blows and holds the choke open, which allows the unit to run. This is a very simple, easy to understand passive type of system that is working perfectly for us.

I happened to have the brass fitting (which would have cost about $3.00) and scraps of the black plastic pipe. The total cost amounts to that brass fitting, two plastic elbows (60¢ each) and the spring (40¢). Had I bought everything for this modification, it would have cost me well under $10. This allows us to utilize the automatic generator start/stop module, making our generators fully automatic. While I don't have that part tied in yet, the automatic choke for these generators that I have built is a great success. It works perfectly. I made a video of the first automatic choke, and while I had to pull the rope (this generator hasn't been in service since last January and I had the battery on another generator), you can see it working.

This method is a lot easier and cheaper to manage than solenoids and all that. It works pretty much exactly the same as the automatic choke on lawnmowers and pressure washers. I hope this video helps others who might be dealing with this exact same situation. I can tell you, I truly believe that "Simple is Beautiful" and that this automatic choke works very well. I will be adapting the other generator in the exact same way.

Here is a link to the video on YouTube:


  • JBish130JBish130 Registered Users Posts: 8 ✭✭
    If the link doesn't run, (it isn't running for me right now) just search youtube for AutoChoke and Jeff Bishop.
  • BB.BB. Super Moderators, Administrators Posts: 30,721 admin
    The link is working for me--Also, I made paragraph breaks in your post--Usually much easier to read vs a "wall of text".

    I worry about automation--If the choke fails, will the starter crank forever (and overheat/kill battery). etc.

    Also--with the choke turning on as the engine ignition is turned off (?), this could bring in raw fuel and wash down the cylinder walls/valve guides. Not great for engine life.

    But I agree that auto-choke/remote choke would be really nice for many folks.

    Good luck!
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 3,334 ✭✭✭✭
    edited October 2016 #4
    Congrats on making that work so far. Yet BB raises important concerns.

    On another note, it sure seems like many of our posters are partial to gigantic inverters with small to moderate battery and solar arrays. I suspect that consequent problems drove many of them here. Then we have waynefromcanada....sipping on a 300 watt inverter while running three separate refrigeration units! Guess most of us made a controversial move somewhere along the line.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • jonrjonr Solar Expert Posts: 1,379 ✭✭✭✭
    Most chokes depend on something heating up - and I think there is good reason for that.  But if your's works even in very hot and cold conditions, great.

    I am available for custom hardware/firmware development

  • t00lst00ls Solar Expert Posts: 234 ✭✭✭
    I had thought about using an automatic choke....instead I opted to convert to propane, which doesnt need a choke

    it is also cheaper than using gasoline...and still yet, cheaper than buying electric from a utility company......

    the power company here charges about 0.09 a kilowatt....and its still cheaper
  • MarkAllenMarkAllen Registered Users Posts: 2

    I remote start my generator from inside my cabin, but it requires a manual choke to start. I have installed a 12 VDC solenoid connected to choke lever and wired it to the starter, so it energizes when starter is energized. Hardest part is shaving off some of the restriction on the choke lever (behind red circle) so solenoid has the power to pull choke in.
  • mike95490mike95490 Solar Expert Posts: 8,868 ✭✭✭✭✭
    MarkAllen said:

    I remote start my generator from inside my cabin, but it requires a manual choke to start. I have installed a 12 VDC solenoid connected to choke lever and wired it to the starter, so it energizes when starter is energized. Hardest part is shaving off some of the restriction on the choke lever (behind red circle) so solenoid has the power to pull choke in.
    Clever, and I like that.  Do you have any problem with the engine stalling out when you stop cranking and ALL the choke goes away ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • MarkAllenMarkAllen Registered Users Posts: 2
    No problem with choke closing once the starter switch is released. At least with my generator it is the perfect amount of choke and the engine fires up immediately.
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