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The Autochoke Side Project


I started to build something here I thought might be of interest.
I have been fascinated by all these new mowers with very good choke systems and frustrated by the lack of a decent automatic choke for clones so I decided to graft the Kohler system to mostly Chinese clone of mixed parts from a generators and utility engines.
I want to build something that will start automatic with just a simple stop run switch to activate it.

First mock up.
As you can see I need to make some exhaust parts and some linkages will need to be worked on.
I might have some governor issues from the looks of things.
But its a start...



Re: The autochoke side project

Do not take this wrong, I like people trying new ideas. Maybe a less complicated system would be a simple primer bulb hooked to the carb vent????

Elden DuRand

In Memory Of
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Re: The autochoke side project

Do not take this wrong, I like people trying new ideas. Maybe a less complicated system would be a simple primer bulb hooked to the carb vent????
Now, what's the fun in that??:)


Re: The autochoke side project

Maybe a less complicated system would be a simple primer bulb hooked to the carb vent????
That might work if I was there to prime the system for a start, but I have something little more challenging in mind for this.

It must start on it's own accord.
Its primary purpose will be a supplementary power supply for some inverters and a UPS.
I thought about making a fully adjustable 3 stage battery charger option and maybe a portable inverter generator.
But first it has to be able to start automatically, the rest I can add later.

Its kind of complicated looking isn't it?
What you see is a complete choke system from a XT149 mower adapted to a clone carb.
Kohler abandoned this system several years ago because of its complexity.
That they use now has no vacuum choke break but a simpler mechanical linkage connected to the throttle.
I could have used that, but I felt it might not work with with my automatic idle control.

Here is the parts break down if you interested.

Bugger I have to go to work now.
Have a nice day guys...

John Newman Jr.

Last Subscription Date
Briggs & Stratton used a system recently that held the choke closed with a fairly weak spring when the engine was at rest (shut off). A thermo operated lever attached to the muffler along with an air vane lever would open the choke when the engine started. The way I understood it to work, the air vane wanted to open the choke immediately on starting, but the thermo lever held back until it saw some heat.


we replaced several of those thermostat assys on equipment 2-3 years old
I was aware of a lot of problems with this system.
The donor mower that I stripped looked almost new and my best guess it it was given up on or damaged for some reason.
I tested all the parts out and the by metal spring moves as well as the vacuum pull off works.

One things that is absolutely wrong with the Kohler autochoke is there is no adjustment.
I plan to address that as you can see I already removed the backing on the thermostatic spring and will make a holder for it that lets you turn it "rich - lean"
as required.
I might even do something with the linkage for the pull off if I think it needs some adjustment, but for now I think its OK.

I need to do something with the muffler.
If you look close I have it mounted upside down in the picture.
Maybe I re-weld and rework it that way, or I could make something up from scratch with an empty propane cylinder, or I could use a generator muffler but its very large.

Its cold and raining outside and I don't feel like warming up the shop so I think I will just type and ponder the exhaust today


Most standby units use some sort of a choke system.
These first two use a bymetal spring to hold the choke partly closed until warm and a solenoid to pull it completely closed while cranking for full choke.
A Generac uses this part

Onan, Kohler and Chrysler used this.

Some use manifold vacuum only
Briggs used a chamber and diaphragm to pull the choke open against a weak spring.
This was a simple idea on the Pulsajet carbs because the diagram and chamber were already there for the fuel pump.
They simply added another chamber spring and rod for the choke

I am using a combination of vacuum and thermal spring like most later automotive application used because I feel its a bit less likely to flood out a warm engine.


The Generac part is electrically heated and electric operated.
The divorced choke I am using is manifold heated and vacuum operated.
I think I rather go with the old timey parts on this one.
And as a bonus Kohler parts are clone Honda so all the rods linkages and bell crank were made to fit the carb.
The Generac might have been more work.

I think I am going to make a simple packed stuffing muffler out of a propane cylinder for this some other time.
I will rework the Honda part for now and live with the noise.


In Memory Of
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Looking into replacement for my autostart Kohler carb, I looked into adapting a Chinese scooter carb. Rather than chokes they have a solinoid that opens a separate rich fuel port. Would need a shutoff timer, but would sure be cheaper. Can even still get fully adjustable carbs. Available from 50cc up to 750cc sizes.

(Seems a bit bland for my 3,000th post... ah well.)


Did some exhaust work to day and make some parts.
Nothing to show yet and I am really tired after a long day at work.
Tomorrow I will start welding and should have something to show.


Still in a weather related holding pattern.

I will pick this up again in the week, I hear the temperature is going above freezing.


Every time I see this I keep asking what the heck is a Artichoke side Project. Then I read it again and see it is Auto Choke.
Hey that sounds a lot more interesting than what I am doing.
Another day and more nothing done.

I made a longer link bar for the carb and I made a nice steel plate to act as a heat soak.
I tinkered a little and decided it was a lot easier to play with the dogs for a while.
But coming back to this I think I am going to cut the muffler again and roll it over another 180 degrees.
I looked at my link bar and I think I will make an even longer one now and a brand new bracket too.

On the engine front I have a nice used Liffan 196 that's waiting on a midlife refit.
I might use a crank from a pump that is threaded with no keyway. I'll hand cut a wood ruff key slot and weld it then file back t fit properly with a pulley.
I found an electric start kit from WASP brand engine I got at tool town in the defective mark down bin.
Its got a broken crank and has been abused, I had it running with that pump crank, but its not a very well made engine ( about 10 years old ) so I am not inclined to use it.
I have a 5 amp lighting pack from Baja minibike I am going to used with the electric start kit from the WASP.

I will put a pump crank in a minibike engine with with a carb from a generator.
And I need a governor so I will take that from the WASP too.
I have a race head I no longer need that I was going to use from a Predator 212 all welded up and very cool looking but not of any real use.
In real life it looks a lot better now that it did at this stage.
Its a head modified for a 70mm bore engine and I am going to build a 68mm engine this might change in favour of just a stock 23cc head for now.
Later though I would like to put an 18cc or so just for a slight boost in compression.

The electrics end of this will be a challange.
I want to turn a 100 amp FORD G1 alternator that has been souped up itself to 150 amps.
Its unlikely to do that very effectively....
I will drive this with a pair of 4L belts off a 4.25 drive pulley to the 1.5 inch alternator pulley ( remember I said this was souped up alternator, I think all they did was increase the drive ratio and put a bigger set of diodes in it )

Here is the plan.
A simple on off switch will start the engine and once rolling a relay will pick up and drop out the starter through NC contact.
I will have to tinker with some relays to get the pick up voltage right.
I am going to use a Klixon as a safety to shut off the starter in event of non start condition and I have some nifty latching relays I think I will use to lock on a fail to start just so nothing is ever damaged.

The Ford alternator has no regulator.
I want a three stage battery charger with an auto start function.
I think an Arduino will work for this to drive the field through a power MOSFET.
This will leave the Arduino with a lot of idle time each loop so maybe I will add a servo to control the RPM too and slow this right down for a light load or 3rd stage of charging.

If I have a remote start I should probably add a low oil shut down too now that I think about it.
Maybe a different block would be a better choice.
That CEP engine in the previous pictures has this feature, but it does not have tapped holes for a starter or lighting pack.
I really want that lighting pack so I can sense crank speed ( like a tach generator ).
I will want to use a couple of pots to sense throttle position for load sensing.
I also have some nifty shunts I could rig to read the actual alternator load, but that would require some isolation to protect the Arduino from voltage spikes and I don;t know a quick easy way to make a signal isolator.

This project has become ambitious...


When I said it was a side project I was not kidding.
But I got back to it and here we are done.
It has some teething pains but it does choke and start.
Bad news my carb is awful, I started with a garbage carb because I was not sure this would work and I ended with a garbage carb that works poorly.
Some issues on the low side probably corrosion and plugged holes under the welsh plug.
And my choice of test engines might seem odd, but that uses many of the same parts you would have on a generator so once I get the bugs worked out it should adapt easily.

Lucky for me the choke pull off and support I made clears the Champion air filter.




Nay a comment?
Well I was real impressed with meself.
Everything still fits and works in the stock locations with this new choke kit in place.

On to phase two the electric start and auto crank cut out device.....
I have an idea on that I found these nice Bosch auto relays rated 12/24vdc and after playing with one I found it will pull in as low as 6 volts.
If I stick a magnet to the side to bias it a little I can get it to still pick and drop out even lower.
So I will use this to lock out the started using the clone lighting package as tacho-generator.

New problem:
The Champion block was never drilled for a lighting package or starter.
I am going to have to drill and tap this by eye and hope the bolts line up


How did it turn out? My Inverter/Converter/Charger has a low battery auto-start function I'm playing with. Luckily the BGA runs on propane, so I don't need to worry about a choke.


What I have is working well.
The real problem with the original Kohler autochoke seems to be a tolllerence stack up on the factory set springs.
Mine is adjustable so I can dial as much cold tension as I want on it for a cold start.

New problem is no high idle cam and no accelerator pump to prime the system with fuel.
This means there is a dead zone where the choke is hot enough to be open, but the factory carb low side jetting is so lean it would like some choke to start.
Solution is to richen the low side, but this is a non EPA or CEPA compliant modification.
This is a legal problem not a technical problem...

Phase two of the build will start soon
I got the choke working and the cranking circuit working and the cut out working. ( Switched from a Champion block to a Liffan block now, went to a different flywheel and coil arrangement by Lonclin for a 60 watt lighting package )
Now I need to build the electrical end of it.

---------- Post added at 08:45:52 PM ---------- Previous post was at 08:44:01 PM ----------

How did it turn out? My Inverter/Converter/Charger has a low battery auto-start function I'm playing with. Luckily the BGA runs on propane, so I don't need to worry about a choke.
Still plucking away.
This is a side project and there are other jobs ahead of it


Snow has come and things ground to a stop.
I forgot all about this untill I heard about Angrysailors misfortune.

I am also knee deep in the Frankenstein Generator now over in the Onan forum ( part kohler, part clone and some Onan green to make it more confusing ).

I have to quit working, and typing ( and drinking ) and all those other distractions that get in the way of building stuff for stuff's sake.