Compression Guage adapter

[Lone Wolf]

Maybe it does matter read this.
https://mullengineering.com/rt/files/2_tech_docs/THE TRUTH ABOUT COMPRESSION TESTING.pdf

 

[Lone Wolf]

If tightening up the Squish increases comp then i bet its the same filling some of the void with more plug ...maybe a different ratio of increase but a increase never the less I believe.
Be interested if you do test it....if you have a gauge accurate enough to measure it.

https://mullengineering.com/rt/files/2_tech_docs/THE TRUTH ABOUT COMPRESSION TESTING.pdf

 

[stihl saws]

I'm sure it has to change, but being able to accurately measure it will be the hard part.

 

[Simondo]

https://mullengineering.com/rt/files/2_tech_docs/THE TRUTH ABOUT COMPRESSION TESTING.pdf

https://mullengineering.com/rt/files/2_tech_docs/THE TRUTH ABOUT COMPRESSION TESTING.pdf

Logic prevailes

 

[Keith Gandy]

Im not understanding what yall r saying. Hoses and adapters should be standard length and not protrude into the chamber but only fill the gap like a plug?

 

[huskihl]

All depends on where the bottom valve is. If there's an adapter on the end of the hose, the reading will be slightly lower.

 

[Keith Gandy]

All depends on where the bottom valve is. If there's an adapter on the end of the hose, the reading will be slightly lower.

I see what u r saying. Ive never fooled with adapters but only hoses of different sizes

 

[huskihl]

I never did either til a valve in mine went bad. Couldn't find valves, so i mistakenly bought a tester without a bottom valve. Needle would rise, but only registering about 5 psi on the gauge. Basically, everything between the cylinder and the lowest valve becomes part of the combustion chamber

 

[huskihl]

Additionally, everything between the bottom valve and gauge accounts for the # of pulls to get to max compression reading. A hose with twice the volume requires 2x the # pulls

 

[idiotwithasaw]

I wonder if anyone has tried using something like play dough to test how much volume is needed to achieve a desired compression reading. Put a layer so thick on the piston or in the top of the cylinder and test, then test again.

 

[Guido Salvage]

I think this Mity Vac tester I found for $10 will handle any application I have.

 

[Lone Wolf]

I think this Mity Vac tester I found for $10 will handle any application I have.

View attachment 23873

Dang it man where do you keep finding all this stuff so cheap? You seem skilled at it.

 

[idiotwithasaw]

Well his name is Guido Salvage

 

[panteliss]

I had a debate about the longer or shorter threads changing the compression with the local small engine repair shop. I said it did change the numbers because it changed the volume. They both told me no but when I asked why not and explain they couldn't?

Too much headache for a chainsaw or a trimmer?? dont worth

 

[panteliss]

Dang it man where do you keep finding all this stuff so cheap? You seem skilled at it.

Relax friend are not the NASA tools , if you go to ebay you will see tones of theese tools for about 30-40 dollars

 

[panteliss]

 

[Guido Salvage]

Dang it man where do you keep finding all this stuff so cheap? You seem skilled at it.

Found in a pawn shop around the corner from my office. It was in a display case with the lid closed and marked $10. I had him dig out the two impacts (a Mac and a Blue Point) and got all of it for $50 out the door.



The belt sander cost me another $30.

 

[CR888]

I wish I was half as good as Guido at finding deals on tools. He is good at it!

 

[CrufflerJJ]

Where can I get an adapter to use on the newer saws with the smaller plug hole?
I've got a 550xp and an ms211 that I would like to check for various reasons.
Also how much margin of error does an adapter add?
Thanks all.

Back in December, I had an online discussion with Brad Snelling about this same issue. I have a compression gauge I bought from Bailey's. That gauge doesn't come with a 10mm adapter for testing saws with the dinky little spark plugs, so I bought a 14mm-->10mm adapter (a threaded cylinder of steel with gaskets to seal either end). It has a ~1/8" diameter hole running through it.

When testing my 2014 vintage 562XP when it's cold, I got a massive (!!) 118 PSI after about 5-6 pulls. This sucks, so I pulled the muffler & checked the piston, which looks just fine.

It seems that you need a Schrader valve at the end of the 10mm threaded adapter or hose or whatever you use. My adapter has no such valve. Brad explained that by doing so, you basically add the volume of the adapter to the volume of the combustion chamber (when the piston is at TDC).

So I pulled out my JB Weld, and filled the 1/8" hole as best I could, carefully packing it into the adapter with a toothpick, cured the epoxy with a hot air gun, then drilled a wee little hole through the adapter. I'm sure it's not perfect, but I ended up filling 1.6cc of dead air space (as measured by water displacement & my reloading scale). Compression testing with the epoxy filled adapter gave me a pressure of 142 PSI.

So I'm not sure how accurate my 142 PSI reading really is. I'd read over on AS about somebody else testing their 562XP with a 10mm adapter vs the "real" gauge, and they saw 130 PSI vs ~160 PSI with the real gauge.

 

[idiotwithasaw]

If someone had access to a machinist that could turn threads I'm sure one could be made to work with a valve