Stihl Saw ID

[ZeroJunk]

You missed the sentence where he wrote “purge valve” anyway all good. Just confirming they’re a purge not a primer.

Purge valve is more correct I'm sure, but most people call them primer bulbs. Just cause that is what they call them . Either way it pulls fuel up through the carb and back in the tank to fill the carburetor. As opposed to a fuel injected saw just to make it more complicated. Or, a mower and at least some weed eaters etc. that squirt fuel straight in the barrel.

The decompression valve is on the cylinder somewhere and has a tiny hole to let some of the compressed air out until it fires and slams it shut.

Some of those saws like you have would have a decompression valve on the side of the cylinder just in front of the top handle on the right, or at least the IPL said they did.

I have never seen one. Matter of fact I have never seen a Stihl saw with a decompression valve on the side 90 degrees opposed.

But, there is a lot of stuff I have never seen.

It would appear that your saw does not have a decompression valve, but it could be hidden behind the handle in the photo.
It does have a purge pump or primer bulb on the side, whatever is customary to call it.

See a few of those.

In general I don't know why Stihl markets this or that here or there. But, we have never sold that series of homeowner saws with decomp and apparently nobody else around here either.

We have gotten a lot of MS250's back from older gentlemen who could not start them. Decomp would have been nice.

 

[ZeroJunk]

No, you were the one claiming we were misnaming the decompression valve as a primer- I merely pointed out these saws are available with both a purge valve and decompression valve- the manual on the USA site discusses the models fitted with decompression valves on page 38, in amongst the starting procedures section.

I see that in the manual. I have never seen one in the shop or on the shelf. And, it was a very popular saw.

So, if his has it that's a good thing. Can't tell from the photo so my mistake.

 

[Captain Bruce]

That's what it looks like to me. Nice and clean.

Used engine oil makes things look dirtier than they are.......when they a filthy

 

[Captain Bruce]

Hey guys, came across this saw, the model plate is either AM or the original numbers just worn off. Any idea what it is? 250c is my guess, but a second opinion would be appreciated.

Has a decomp if that helps? View attachment 1083337

WASH that neglected beauty right there.....hit it with some GUNK, blast it with your hot water hose.........the debris will fill the Cracks in your patio, and keep the weeds down.

 

[Captain Bruce]

You missed the sentence where he wrote “purge valve” anyway all good. Just confirming they’re a purge not a primer.

All 2-cycle engines will have a dry carb when ready to start. The last remaining mixture is exhausted by the other cycle, when spark is shut off.
The carb will have a draw hose, and a hose that pushes fresh fuel, "thru" the carb to displace the air. That hose runs next to the draw hose, and back into the tank.

The exercise is commonly called, purging. The clear bulb is pressed 5 times, the first 3 get the air out, the final 2 draw fuel into the carb and out into the cylinder. FULL choke provides the fuel mix for starting. Once it burps, the choke is opened, and the engine always re-starts, becuase it always has fuel.

Some of the odd terms, include "purge valve" which is NOT what the bulb is doing. There is no on/off, therefore, there is no valve operation.

The bulb is properly called the "primer bulb", in the instructions, manuals, and IPL's.......so it is...... the Primer Bulb. Plus, its a Bulb.

The engines pushing 70cc's, will normally have a pressure release valve in a port on the cylinder head. Intended to ease the initial dry start of such a large engine, their purpose, as a real mechanically valve, is to release a slight measure of the compression these large engines create. In doing so, the operator is able to pull the recoil starter with a slight decrease in pressure. Hence, the blue knob "de-compression valve".........
De-Comp for short, and she has a Spotify play list...

 

[Vintage Engine Repairs]

Some of the odd terms, include "purge valve" which is NOT what the bulb is doing. There is no on/off, therefore, there is no valve operation.

The bulb is properly called the "primer bulb", in the instructions, manuals, and IPL's.......so it is...... the Primer Bulb. Plus, its a Bulb.

The system does have an on off, it’s the duckbill valve in some systems, or in the likes of stihl it’s a one way check valve.

The bulb purges the air from the carb through the vacuum they create.

It’s not a primer bulb, it doesn’t prime anything - it doesn’t push fuel into the carb to prime it. It purges air. A primer is what is found on lawn mowers that shoot fuel directly into the intake manifold.

Edit:

Either way it’s all semantics. I appreciate people helping me with the saw. That’s what matters here

 

[HansFranz]

I don't see the point of primer bulbs, unless the point is "let's try to get saw buyers to buy moar parts that wear out faster."

I had a Dolmar tree saw whose "primer bulb" dried out and cracked/leaked and I didn't have time/know-how to replace it, so I just left the roached primer bulb in place and used the choke instead to start the saw and that worked fine for years. I left it that way for a few years and never gave it another thought until finally the saw crapped out and I couldn't fix it, and I took it to a shop, which installed a new primer bulb, although that wasn't the problem that caused it to not run...

Just seems like a worthless, pointless, plastic doo-dad that's destined to dry out/crack and become even more useless fairly fast, like a condom rolled onto a bar and chain...

 

[Mad Professor]

I don't see the point of primer bulbs, unless the point is "let's try to get saw buyers to buy moar parts that wear out faster."

I had a Dolmar tree saw whose "primer bulb" dried out and cracked/leaked and I didn't have time/know-how to replace it, so I just left the roached primer bulb in place and used the choke instead to start the saw and that worked fine for years. I left it that way for a few years and never gave it another thought until finally the saw crapped out and I couldn't fix it, and I took it to a shop, which installed a new primer bulb, although that wasn't the problem that caused it to not run...

Just seems like a worthless, pointless, plastic doo-dad that's destined to dry out/crack and become even more useless fairly fast, like a condom rolled onto a bar and chain...

Yup, chokes don't wear out.

If saw sat overwinter and won't start, give it a thimble of mix in the carb.

 

[ZeroJunk]

Well, they are mostly never on "pro" saws. The primer on a fuel injected saw being different.

So, for all of you "know it all's" there are hundreds of users out there who don't give a **** about what you know about saws and just want to get some limbs off their property.

Purge pumps, primers, whatever, makes it easier for them to do what they want to do while not giving a **** what you think about it.

 

[Bob Hedgecutter]

Well, they are mostly never on "pro" saws. The primer on a fuel injected saw being different.

So, for all of you "know it all's" there are hundreds of users out there who don't give a **** about what you know about saws and just want to get some limbs off their property.

Purge pumps, primers, whatever, makes it easier for them to do what they want to do while not giving a **** what you think about it.

Not all pro saws are injected though- only one of them thus far.

 

[ZeroJunk]

Not all pro saws are injected though- only one of them thus far.

My partner in crime who is a legitimate Stihl tech with a diploma and all that has been working on a TS500I which is a fuel injected cut off saw. It has no fire. The diagnostic program will not detect the computer in the saw. So, he replaced the computer. Program still will not detect it. So, he pulled the fly wheel and the generator and everything under there had a layer of brick dust on it. Cleaned all of that off and still nothing, but he had put the old computer back on the saw. So, he took the old computer back off and replaced it with the new one. Again. And, got it running.

Hell, I can put a new top end on a TS420 in 30 minutes. Maybe the wheel does not need to be reinvented.

Sorry for the tangent.

 

[Vintage Engine Repairs]

Finally gotten around to tearing in to it, it’s a 40mm bore so it’s an ms 230c-be

Thanks for all the suggestions and info.