Please explain primer bulb function

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Lots of types and all have different advantages. Primer that will inject small amounts of fuel directly, primers that will push air into the carby to force fuel through the main jet and into the venturi, purge bulbs that will suck fuel through the carb and even a tickler that will push the float down to flood the carb bowl and thus go into the Venturi ect .

I don’t like any, if I was to be forced to have one, I’d go for a purge to remove any air in the whole carb.

I’ll take a choke and no bulb any day.

I choose saws old enough not to have a primer bulb. I like more metal and fewer dorky plastic gimmicks. I have had more problems with these than they fix.
 
When you are operating the primer bulb, as soon as you can feel that you are squishing fuel through the bulb rather than just air, it's time to stop pressing it. If it isn't pumping fuel, there is an air leak somewhere in the fuel supply, leaking nozzle check valve in the carb or maybe a bad primer, any suspect issue with the primer can be resolved by disabling it, just pull the primer line off the carb, plug the line and push it back onto the carb. Without the primer you will just have to rely on the choke to fill the carb with fuel, a little more pulling.

My son showd me a trick...turn the weedeater or chainsaw upside down to make sure fuel goes to the primer bulb if it pumps nothing but air. Sometimes helps prime the primer bulb...stupid thing.
 
Well, if we are referring to the bulbs found on 2 stroke power equipment it also helps the recoil last longer. Prior to the " primer bulbs" being fitted the integrity of the fuel pump side of carb was depended on to maintain siphon.
Typically it would take a few attempts to rebuild the siphon factor. Primer bulbs helped remove these "attempts"...Echo PB210e blowers actually had a check valve in the fuel line to help out prior to primer bulbs (circa 1984 or so).
 
What has not been mentioned is that with many newer saws they run very lean. This raises the cylinder temperature and the heat can literally boil the mix in the carburetor. The primer bulb will supply fresh cooled mix to the carburetor and make starting easier.
 
The primer bulb reduces the number of pulls needed to start the engine when cold. That's about it. Then when they break down with a small crack, the saw won't even run and many times has to be taken back to the dealer for an expensive repair. 'Nuff said.
 
I work on my own chainsaws and have learned from experience how primers bulb 2 cycle equipment operates with and without primer bulbs.

I've noticed on chainsaws, usually Craftsman or Poulans if stored for few days, weeks or months with a dry carb they will usually start easier if they have a primer bulb. If I pull a non-primers bulb 2 cycle engine a few times in cold weather when coming out of cold storage and with a dry carb I just grab my mixed gas primer squirt bottle and prime into the carb throat or into the muffler so as to get a primed start.

I also keep spare primer bulbs ready and I do not fully press/collapse them when priming in cold weather so as to reduce the chance of causing a plastic bulb cold weather failure.
 
My son showd me a trick...turn the weedeater or chainsaw upside down to make sure fuel goes to the primer bulb if it pumps nothing but air. Sometimes helps prime the primer bulb...stupid thing.
It is a fact that as fuel line ages, it often STIFFENS to the point where it will NOT fall to the low point in the tank; as it ages further, it will reach a point where it CRACKS and sucks air.
 
My son showd me a trick...turn the weedeater or chainsaw upside down to make sure fuel goes to the primer bulb if it pumps nothing but air. Sometimes helps prime the primer bulb...stupid thing.
If this happens, it’s because you have a leak in your fuel system. Either lines or carb and the vacuum you are creating with the bulb is drawing air rather than fuel. Turning it upside down allows gravity to take effect and thus you can draw fuel. It’s a sign to dig into the fuel system and fix the problem :)

Put some pressure into your fuel line and spray them and carb with soapy water and you’ll likely find it. If you don’t, remove the metering leaver and then replace the gasket, diaphragm and cover and repeat
 
I suppose it depends a little on which saw you run, but fuel line and purge bulbs are generally cheap and usually easy to replace. I run an ethanol mix because that’s what’s available in the gas here. Therefore, I expect to replace primer, fuel lines and diaphragm. But it’s so cheap and easy that fresh lines and primer are a small price to pay for reliability. Typically the fuel in take line with the filter that sits in the fuel hardens first. When it does replace everything.
 
Lots of the replacement tygon fuel lines and primer bulbs are the China made stuff and we pay full price thinking it's the good stuff. China can really make the poorly made stuff look like the real thing now days.
I've seen old USA made primer bulbs last for ever until the ethanol came alone, but the china stuff don't last very long.
 
If this happens, it’s because you have a leak in your fuel system. Either lines or carb and the vacuum you are creating with the bulb is drawing air rather than fuel. Turning it upside down allows gravity to take effect and thus you can draw fuel. It’s a sign to dig into the fuel system and fix the problem :)

Put some pressure into your fuel line and spray them and carb with soapy water and you’ll likely find it. If you don’t, remove the metering leaver and then replace the gasket, diaphragm and cover and repeat
Have also had some filter/weights just fall off fuel line inside tank, so line sticking up in air inside tank. NEEDS Investigating, when not working right; don't IGNORE symptoms, LOL
 
I have a Gardenline (ALDI) 41cc chainsaw, not used for a couple of years. The purge button does not seem to be moving fuel, just air, and ON RELEASE makes a whistling noise that seems to come from the front (saw blade end) of the engine. I have checked the filter which looks OK and tried without the filter to be sure. Does this make sense? I can't see clearly how to open the main casing to get inside even!
 
I have a Gardenline (ALDI) 41cc chainsaw, not used for a couple of years. The purge button does not seem to be moving fuel, just air, and ON RELEASE makes a whistling noise that seems to come from the front (saw blade end) of the engine. I have checked the filter which looks OK and tried without the filter to be sure. Does this make sense? I can't see clearly how to open the main casing to get inside even!

You can find lots of you tube info about how primer bulbs work and their function and how to test them.
 
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