CS-2511 Compression?

[MAWoodsman]

Curious if anyone out there with a 2511 can report back with what they get for compression?

 

[Vintage Engine Repairs]

2 stroke saws are fairly generic.

180+ is very good
150 is normal
125 is where you’ll start getting running / non start issues

Worth mentioning the importance of a shrader valve in the end of the adapter that goes on the spark plug hole. Without one the tube acts as part of the cylinder volume reducing your compression ratio and gives you whacky low readings.

 

[MAWoodsman]

2 stroke saws are fairly generic.

180+ is very good
150 is normal
125 is where you’ll start getting running / non start issues

Worth mentioning the importance of a shrader valve in the end of the adapter that goes on the spark plug hole. Without one the tube acts as part of the cylinder volume reducing your compression ratio and gives you whacky low readings.

The 2511 is a small 25cc saw. The piston isnt much bigger around than a quarter. When i check compression, its 91psi. It fires right up and runs good.
But i had heard what you mentioned above, and 91psi has me thinking something is going on?

Was hoping someone here could check the psi on their 2511 to compare

 

[Vintage Engine Repairs]

The 2511 is a small 25cc saw. The piston isnt much bigger around than a quarter. When i check compression, its 91psi. It fires right up and runs good.
But i had heard what you mentioned above, and 91psi has me thinking something is going on?

Was hoping someone here could check the psi on their 2511 to compare

The engine capacity doesn’t matter, your value of 91psi is incorrect. Read the final paragraph of my first comment - that’s the issue you have. It’s an automotive gauge you have, not a small engine gauge.

It will stop running circa 125psi.

 

[MAWoodsman]

The engine capacity doesn’t matter, your value of 91psi is incorrect. Read the final paragraph of my first comment - that’s the issue you have. It’s an automotive gauge you have, not a small engine gauge.

It will stop running circa 125psi.

The gauge I have has the Schrader valve on the end that goes into the spark plug hole. The max psi it can hold is 300.

 

[huskihl]

2511 has about 180

 

[huskihl]

And I agree with Tom. Something may not be right with your tester. But it’s entirely possible that it has worn through the plating and the cylinder is shot.

 

[mountainlake]

At 91# it's not going to run. Steve

 

[Vintage Engine Repairs]

The gauge I have has the Schrader valve on the end that goes into the spark plug hole. The max psi it can hold is 300.

Take a picture of the end of the adapter, A friend thought he had an shrader, it looked similar but it wasn’t. Here is a picture of his.




Here is what a shrader looks like



If you remove the tube from the compression gauge, can you blow and suck air with your mouth throttle the tube?

 

[MAWoodsman]

Take a picture of the end of the adapter, A friend thought he had an shrader, it looked similar but it wasn’t. Here is a picture of his.

If you remove the tube from the compression gauge, can you blow and suck air with your mouth throttle the tube?

Mine looks similar to the one in your bottom pic. I tested it on my 4910 and got to about 131psi in 5 pulls.

 

[Vintage Engine Repairs]

Mine looks similar to the one in your bottom pic. I tested it on my 4910 and got to about 131psi in 5 pulls.

upload a pic of the shrader, either way that saw isn’t running at 91 psi.

 

[MAWoodsman]

At 91# it's not going to run. Steve

It definitely runs.

 

[Vintage Engine Repairs]

What I’m saying is 91 psi isn’t enough for a 2 stroke chainsaw to run. Your gauge is incorrect. Be it the lack of shrader or the gauge itself.
I’m not going to go back and forth on the subject to debate it. It’s a fact.

Edit: huskill says his 2511 has 180 psi of compression so you have your answer, regardless of if you want to believe your saw actually has 91 psi or not.

 

[MAWoodsman]

upload a pic of the shrader, either way that saw isn’t running at 91 psi.

Here is a pic of my gauge valve

 

[MAWoodsman]

What I’m saying is 91 psi isn’t enough for a 2 stroke chainsaw to run. Your gauge is incorrect. Be it the lack of shrader or the gauge itself.
I’m not going to go back and forth on the subject to debate it. It’s a fact.

Edit: huskill says his 2511 has 180 psi of compression so you have your answer, regardless of if you want to believe your saw actually has 91 psi or not.

Apologies, i wasnt trying to say u were wrong, was just trying to wrap my head around it. Is there a reliable gauge you would suggest i use?

As another test, i used a scale to measure how much pull force it took to pull the motor over (not start it, just a pop or two)

On my 2511, it was about 17lb of pull force, on my 4910 it was about 30lbs.

 

[Vintage Engine Repairs]

Apologies, i wasnt trying to say u were wrong, was just trying to wrap my head around it. Is there a reliable gauge you would suggest i use?

As another test, i used a scale to measure how much pull force it took to pull the motor over (not start it, just a pop or two)

On my 2511, it was about 17lb of pull force, on my 4910 it was about 30lbs.

No no all good, I just don’t have any interest in going back and forth debating it, it’s so, so common that people have your issue, with your psi readings on saws that run and then they figure out their gauge is not suitable.

I don’t like recommending something I haven’t used and because I’m in Australia you won’t have the brand i use. However I have heard of people using mityvac, motion pro, otc & stens. Though do your research to ensure the one you get is suitable. Others will chime in soon

Edit:

Regarding pull force, the size of recoil and flywheel pawl location drastically change the leverage required to pull an engine over. It’s not a reflection on the amount of compression the engine has.

 

[huskihl]

Here is a pic of my gauge valve

Do you need to use an adapter on the end of that hose to fit the 2511?

 

[Vintage Engine Repairs]

Do you need to use an adapter on the end of that hose to fit the 2511?

The weight of the spring on that valve is so important too. Too much (typically found on automotive setups) will also give woeful readings.

 

[MAWoodsman]

Do you need to use an adapter on the end of that hose to fit the 2511?

Yes, there was an adapter to fit the 2511 plug hole.

If anyone can suggest a reliable compression gauge, ill look into picking one up to see how it does.

 

[huskihl]

Yes, there was an adapter to fit the 2511 plug hole.

If anyone can suggest a reliable compression gauge, ill look into picking one up to see how it does.

Is there also another Schrader valve in the bottom of your adapter?