learning about choking a gas engine

Manual choke is fully controllable. The plastic pimples are arbitrary, sometimes you punch 3 times, sometimes you punch 30 times. You have no idea how much gas is going in and it seems to vary time to time. Then when engine starts, it may die and you start over punching your little plastic pimple again and again.

On other hand if you know how to use a choke and from what I can tell, you may even be old enough to remember manual chokes on automobiles, you simply close choke, start and slowly open it depending on how the engine sounds.

Modern small engine carbs are also set at factory to run very lean for pollution reasons. The ability to have control over a choke allows users to over ride such lean setting merely by leaving the choke partially closed. You can mow with manual choke partially closed. EPA wants to usurp this control. You cant mow your lawn while at same time punching the pimple to keep air fuel mix richer. Engines running full governed speed also pollute less thus elimination of ability to control engine speed. And engines can run leaner at higher rpm. So far only on lawn mowers but expect to see such on other equipment eventually.

With a properly functioning carburetor and a properly functioning human brain operating it, a choke will start an engine far quicker than the plastic pimples. As others have said, it takes bit experience with a particular engine and carburetor how to make manual choke most effective.

But if you like plastic pimple fuel systems, for sure you live in best of times to experience them. Punch that pimple! Over and over and over again until you are happy. Or you can buy a can of ether and drill small cheater hole in air filter canister that the plastic straw on aerosol can fits in and give it a shot to start engine. Sure there is a way to automate this process. I remember some older diesel tractors without glow plugs where they had an automated starting fluid setup. You just replaced the can fluid every once in a while. Hey it kept one from having to open air cleaner every time like on some old diesels. Or again you can drill a cheater hole that aerosol straw will fit into.

__________________
"What would you do with a brain if you had one?" -Dorothy

"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman

It's a guy thing.... Each of us takes great pride in being the only member of the family that can start a piece of equipment. It was through many colorful language sessions that we learned you must turn around clockwise two and a half revolutions, alternate from your left foot to your right foot and pull the cord (all done while making sure the centerline of the pulley is in alignment with Capricorn.....

Why would you want to vary the engine speed on a piece of equipment designed to perform its best at a specific rpm? Every engine that I have that is designed to be operate at various rpms has a choke/enrichener. Some of them have the primer bulb also and some don't. My 12 year old push mower has no choke/enrichener and starts every time after a few pushes on the primer bulb. It has a throttle if I need to adjust the motor speed but the governed speed at WOT seems right and works well. If you have to richen the mixture to get it to run right then there is a problem somewhere that you are masking.

I think the "pimple" is more of a primer bulb to get fuel to the carb before the vacuum takes over rather than a choke mechanism.

Like and outboard motor has. Both my outboards have enricheners and primer bulbs and I need to use both to cold start either of them.

Yes you are correct. Even those engines that have the primer bulb ALSO have a Choke.
Even My Brand new weed eater that I just bought 2 days ago, has a "Choke" Plus the Primer Bulb,
So does my snowblower, so does my chainsaw.
It just makes life so much easier "Pushing" in some gas into the carb, then relying on the vacuum from a cold start.
I don't want to have to Pull Pull Pull. I have arthritis and I want the sucker to Start Right away, or as quickly as possible, and that primer bulb has allowed for easy starting.
I want to Pull once or twice and Start. Bingo. And when it is 20 below and you need to Blow Snow I want the blower to START NOW not after pull pull pull.

If you choke a Smurf what color will it turn ???

Mowing weeds is different than mowing a golf course or yuppie lawn. In many situations a slower speed is better. I mow half throttle.

__________________
"What would you do with a brain if you had one?" -Dorothy

"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman

If you actually look at the choke plate on carbs with both a choke and pimple, you will notice the choke is partially disabled by a rather large hole throught the choke plate. A partially disabled choke like this is not effective by itself.

An engine in good tune with a real choke can easily start and run with two pulls. A real choke, not one with a big hole in it will draw gas into carb a lot quicker than punching a plastic pimple a thousand times. Matter of fact with a REAL choke getting too much gas into the carb isnt that hard to do.

Also with the plastic pimple method, unless you are going immediately to full throttle, the engine will stall in cold weather when first started. With a choke you can set it to be partially open so you dont go immediately from super rich to super lean. Engine has to warm up before you open the choke completely. The plastic pimple doesnt allow engine to warm up unless you have somebody running alongside the engine punching the pimple every little bit.

__________________
"What would you do with a brain if you had one?" -Dorothy

"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman

You misunderstood what I said, maybe intentionally, the EPA doesnt want people using choke to enrichen their mandated settings. If you have to have the choke partially closed to run a warmed up engine, then indeed something is wrong. But PEOPLE DO IT so the pimple along with either no choke or a choke plate with a big hole in it is way to keep people from doing this. And modern small engines are set to run as lean as is possible, for pollution control, NOT for your ease of use. Engine running too lean has to run FULL governed speed to overcome this. Lot of them run like crap.

I take it you are not old enough to remember traditional chokes before the plastic pimples. No HOLES in them. Closed, they will suck all gas you need into an engine almost immediately as you crank. The choke plate blocks direct air flow from outside through the carb throat so instead draws fuel through fuel passages in carb. If anything you had to be careful to not flood engine. Getting plenty gas quickly was not a problem. Old engines if they didnt start immediately usually more an ignition problem. Remember those old timers used points and condenser which lot people didnt properly maintain and over years the magneto coil would get weak too.

If you look at your engines you say need both pimple and choke, then you will find a partially disabled choke, the manufacturer drills a big hole in the choke plate. This lets lot air through and doesnt let engine suck gas as effectively into the carburetor. These are pollution control designs to meet EPA demands, NOT there as an actual improvement.

__________________
"What would you do with a brain if you had one?" -Dorothy

"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman

LOL

No why on earth would I want to "intentionally" misunderstand you?

I fully understood what you meant. Unfortunately I am plenty old enough to remember traditional chokes. I have couple in the yard right now in fact. Ahhhh.... the good old days of stuck or broken choke cables.

I am also very aware of the EPA regs requiring most engines to be set to run very lean. I just don't get how this has any significant affect on simple engines designed to be operated in a narrow rpm range. It does surely affect performance type engines which is why there is a billion dollar aftermarket business intended to supply us with the stuff we need to open those puppies up and let the fuel flow through.

Really don't understand the problem with a lawn mower though. Why on earth would you want to throttle it down to mow the heavy stuff? Manicured or golf course would never be used to describe our place.

I understand that things are not as they were. I too am no supporter of the EPA in many cases.

Just haven't had the problems you seem to be having with my stuff.

Maybe there is some money in marketing a NOX system for your lawn mower.

There are better choke cables that dont rust and bind. But if have one of the old spiral wire wound ones, just squirt some ATF or even motor oil on it once in a while. Called preventive maintenance. Rather than a cable I prefer a mechanical choke linkage on the engine itself. My ancient Yazoo mower, when Briggs went bad, I put a nearly new $40 Honda clone engine on it. Instead of a choke cable, I just used a length of baling wire to operate the choke like I did when getting rid of automatic choke linkage on the Briggs. Run it through bit rubber cut from an old radiator hose and it stays at any setting you want. Simple is always better. Engineers used to have the KISS principle (Keep It Simple Stupid). Now rule is make it as complex as you can and add a computer into the mix if possible and for sure whatever you do, dont make it repairable or at least not economically repairable.


I guess I need to turn the question around and ask why you would want to not have control over the rpm of your lawn mower? Do you think full rpm in all conditions is what you need? Have you ever tried running a mower at a slower rpm? I have never found it necessary to run full governed speed for any length of grass. Just wastes more fuel and makes mower noisier. Plus if you are in taller grass, it tends to be more apt to get long stringy lengths of grass wrapped around shaft. My old Yazoo doesnt grind up grass in to a wet pulp, it just cuts it and moves on. This takes LESS horsepower, a lot less horsepower. Think of it like running a brush hog at slower rpm with a sharp blade, run slow, you can make brush hog lay down tall stuff almost like a sickle mower. Well same with my old Yazoo.

I am not suggesting anybody do anything. I am simply stating what I have observed considering chokes and modern EPA engines. I will do everything possible to make the engines I own operate as I want them to operate. Just cause it comes from store set up a particular way, doesnt mean thats only or best way to do it. Usually just means its the way the manufacturer found to make the most profit without totally annoying either govt and consumer. Govt can close them down, but so can consumers, by not buying the product.

Any attempt at commercially selling products to circumvent EPA requirements is going to bite you in the rear. So is running a shop that modifies EPA systems to work better. Even the big corps need tag team lawyers and bunch lobbyists in Washington to avoid getting regulated out of buisiness. But re-engineering things yourself on your own off road equipment at this point is still under radar.

__________________
"What would you do with a brain if you had one?" -Dorothy

"Well, then ignore what I have to say and go with what works for you." -Eliot Coleman

Choke useage varies on the engine. Fundamentally, a choke strangles air flow, increasing vacuum in the venturi, sucking in more gasoline, making the mixture rich. The degree of strangulation and resulting vacuum and resulting enrichment from that vacuum vary with how tightly the choke is closed, and how fast the engine is spinning.

Generally, you start a cold engine with full choke. When it starts, you will reduce the choke to get a smooth running engine. As the engine warms up, you can turn the choke off completely.

One thing that makes many engines entertaining to start is that full choke causes the engine to flood. Then you have to greatly reduce the choke to restart the engine. The classic example of this with chainsaws and the like is them kicking and banging, and maybe even once catching for about half a second. They then flood. You reduce or turn off the choke, yank the string a few more times, and the engine bursts into life.

And then there are enrichener circuits. We can talk about them on another day.