Minimal Compression

[Shaunzo]

Lifetime weekend warrior wrestling with a CS-4600 to determine who’s gonna be boss.
What’s minimum compression this saw should still start and run ?
This thing is flooding like crazy and I can’t figure out why. Ty

 

[Fordiesel69]

Diaphragm? I like to see 90 to 100 on a whipped saw.

 

[Chevboy0167]

Yup.... 100 or less is the standard for a more detailed look into the internals or gasket/seal leaks.

I have worked on an old grey body Echo SRM-210 string trimmer that had 81 and it still started and ran decent... power was a bit low of course.

The guy is still running it as far as I know!

 

[Fordiesel69]

Not sure how they do it but those 21. 2 cc beasts will run almost perfect even with a roasted cylinder

 

[telecasterfool]

have you checked the fuel metering valve? remove the fuel inlet hose, plug it, pull the cord until it's clear of fuel. Squirt a tiny amount of fuel in the carb, choke. see if it starts. All of this will tell you if there is enough compression to run, and if you have spark. The rest of the puzzle is getting the fuel system to properly meter under all conditions.

 

[Vintage Engine Repairs]

Anything below 120psi will be a struggle
to start.

 

[MacAttack]

Agreed... I feel like once a 2 stroke gets below about 120 psi it's time for a top end rebuild.

 

[PV Hiker]

At sea level or at 9,000 foot elevation.

 

[Vintage Engine Repairs]

At sea level or at 9,000 foot elevation.

Very valid I’m right at sea level, 5m above lol.

 

[Shaunzo]

Diaphragm? I like to see 90 to 100 on a whipped saw.

I got 105

 

[J D]

Need to be using a compression tester designed for small engines too, otherwise your readings will be significantly lower than actual

 

[buzz sawyer]

Good read on compression tester. https://www.arboristsite.com/threads/what-compression-tester-are-you-using.378322/#post-8380926

 

[MacAttack]

I use a regular Craftsman compression tester and it works perfect.

 

[Husky77]

I'm sure I posted to a similar question in the pasted so will make this short.
I had a saw with around 60psi, started run and cut perfect. So had my suspicion it was my new gauge, tried a friends and it was over 100 psi. So dicided to get a new gauge, it was up there over 100 psi and run the saw a while then at a quiet time I thought I would strip it and put a new top end, ran perfect as expected but still the same psi so I think this myth it has to be over a certain psi maybe rubbish. Unless you can find out the manufacturer spec for that psi then all your doing is guessing.
The saw is a husqvarna 550xpg and now done many hours of trouble free cutting. Get the right gauge for the job and do the job properly as per manufacturer's spec and you cant go wrong.