Manual chokes: why not?


@VDCdriver I use the same ethanol free fuel in both my 2 stroke powered equipment-- my tiller and my snow blower. My tiller was very difficult to start before using this fuel. The snow blower had no problems on the fuel I mixed up for it, but decided this ethanol based fuel was better for the engine.


Those Popular Science magazines are archived on-line somewhere. I enjoyed those old Gus articles a year or two when I read them again.


OR Google for popular science archives


Lowe’s (and probably also Home Depot) sells the standard two-cycle mix ethanol-free gas (40:1 ratio), the Husqvarna/Stihl two cycle mix ethanol-free gas (50:1 ratio), and the four cycle ethanol-free gas that I buy.


I had a 1963 Chevy II with an automatic choke (push and release the gas pedal before starting to set the choke) that worked very well until the car had nearly 100k miles. Bought a kit from Whitney to convert to manual choke. Pull the control knob out to start then move to about halfway in until some warming, then push the control knob fully in for normal driving. If the motor would threaten to stall while moving off for the first or second time, then the choke control knob was pulled out again for a short time, then halfway in again.

The manual choke was more work and a mild distraction while driving so I took some time to clean the automatic choke to make it work well again. It used hot exhaust gas to heat the spiral bimetal spring that gradually opened the choke as the engine warmed but became dirty from the exhaust gas.

Anybody recall stuck heat riser valves that directed hot exhaust gas heat to the intake manifold with a cold engine?


The ethanol free small engine fuel available to me is sold in gallon cans for about $20 dollars. It’s four stroke specific, it has no oil mixed with it. I don’t believe it contains a stabilizer, it’s custom blended using hydrocarbons that don’t need stabilizers. It doesn’t even have the familiar gasoline smell, instead, smelling a lot like camping cooking and lantern fuel, or lighter fluid.
I love the stuff, my mower starts first pull even when sitting for a year with the gas in the tank. I’ll gladly pay the price in order to not have to overhaul the carb every other time I use the mower.
It’s also not legal for road use, mostly because the price doesn’t include a road use tax.

My mower doesn’t have a manual choke, instead, it has a linkage that chokes the engine when the throttle is full forward, you pull the throttle back a little to take the choke off. I have considered modifying it to be independent of the throttle lever, a separate control, but laziness has prevented me from doing this so far.


Believe it or not, we actually have an older POS truck . . . not a pickup, it’s a fairly large, class 6 truck . . . at work that uses this system

Unfortunately, it’s got amazingly low mileage, so it’ll probably be around for some time

To be fair, though, the truck is in good mechanical shape


My dad had a 1954 Buick that I bought from him in 1963. At any rate, the Buick had a heat riser valve. It would make a terrible rattle when you first started the engine when it was cold. When I was in high school, I had taken the Buick in for tune-up. When the mechanic started the car, it made that rattling noise. When I asked the mechanic about the noise his response was “When the car quits making the noise on start-up, bring it back because you have a problem”. He then got the owner"a manual out of the glove compartment and showed me the section on the heat riser valve. The owner’s manual even described how to lubricate the valve with graphite.


yep, i agree, it was probably used as a selling feature too " buy our car it has an automagic choke,their car sucks because it still has a manual choke"
plus they could add a couple hundred bucks to the sales price by adding a $10 automatic choke.
it`s always about money.


Yes, but EFI doesn’t achieve such “enrichment circuit” by putting an obstruction upstream of the injection point, thereby lowering throttle body air pressure…so you can’t really claim they have a “choke,” per se.


You described what was called ‘white gas’ (the original unleaded) for camp stoves and lanterns (it also worked great in Zippo lighters). Coleman had gallon cans for about $2. We had a local parts and bulk petroleum store (which is still in business as a parts store) which sold it in bulk (bring your own can) for 30 cents per gallon. They also sold bulk kerosene for 15 cents per gallon and 30W re-refined oil for 50 cents per gallon. Of course this was in the 1960s. The military used it until the early 1990s and called it MOGAS.


What lawn mowers are regulated by the EPA you ask? Guess again. About 5 years ago I called Briggs customer support to try and find the correct carb diaphragm for our push mower. I started reading the numbers off the engine plate and the guy said no those are the emissions certification numbers not the model. Its more pervasive than thought. That’s why the new engines have no carb adjustments on them-so you can’t screw up the emissions. Think they are doing it just for the fun of it? Just look on the plates of any small engine and you’ll see the numbers yourself.


I love EFI. I can flop into the seat, insert key, buckle seat belt, put transmission in neutral, depress clutch pedal to floor, turn key to start, and car goes vroom. Of course if the EFI equivalent of a choke fails I cannot install a $5 manual conversion and drive on. I am willing to accept that and pay someone who knows what they are doing to repair it.


I don’t think ‘white gas’ ever had a 94 octane rating though. My grandfather used to buy white gas by the drum from the local distributor and even though it was water clear, it still smelled like gasoline. He used it in his John Deere model A tractor.
This fuel I get has a different odor, sort of like naphtha. It’s made by VP racing fuels.
I’m not sure what in gasoline gives it that “sweet” smell, benzine perhaps? The alkanes, (butane, pentane, hexane, heptane, octane, nonane…etc.) are all completely odorless.


That sounds like a lot of unnecessary work.:slight_smile:


No [kidding], Sherlock, lawn mowers are regulated!!

Why do you suppose:
*Lawn-Boy went away from 2-strokes all of a sudden circa 2000, and there are ZERO 2-stroke mowers on the market today?
*Briggs+Stratton has discontinued all of their VERY popular flathead models, and replaced them with OHV versions?
*Modern mowers run so lean that they surge at idle, and burn valves?
*Modern mowers have check-valve vented caps, so the tank is always at slight negative pressure? (The old ones simply had a pinhole or two in the cap.)

  • Many modern leaf blowers and chainsaws are 4-stroke?

The EPA has been HARD at work making lawncare guys’ lives Hades for roughly the last…8 years or so. It gets to the point, if you get a well-maintained, powerful mower, KEEP IT, because you won’t be allowed to replace it with like kind!


Unfortunately, I think you’re right, db. What a loathsome view of humanity, and individual liberty! To wit: “I know that if I let you touch this, you’ll just [foul] it up somehow, so I’m going to prevent you from doing so.”

When, in fact, a diligent motorist with a hand choke will put out LESS pollution than an automatic choke (which typically isn’t much more advanced than a bi-metallic spring.) But…heaven forbid we TRUST people to be sane and competent!

As I’ve said before, the EPA has varied between indifference and hostility W/R/T the people most directly affected by their (many, many) edicts…


How about a compromise :rolling_eyes:

Equip the car with an automatic choke, but don’t mention it in the owner’s manual

The owner’s manual should instead mention the manual choke, and show where the hand controls are located

That way, the driver will pull the controls out, whether to actually engage the choke, or to hang their handbag, but it won’t actually be connected to anything


  1. We’re EFI now. There’s no chokes to control, db…that ship has sailed.

  2. Lying to my face (a paying customer) is “compromise?!”

  3. Has it ever occurred to you (at least W/R/T lawn mowers) that I might WANT to run my mower as cleanly as possible, and WANT extra control over the enrichment circuit to accomplish that end? In addition to lying to my face, you’d be depriving me of doing better than the “enforced mediocrity” of the automatic choke.


I foresee a day when lawn mowers have some form of EFI. As far as I’m concerned, that day can’t come too soon.
Running the engine lean helps keep down carbon monoxide, but if it results in misfires, the unburned hydrocarbon emissions go through the roof.


Well, remain skeptical no longer, my friend.