Compression tester

[BJD85]

So ive been given a nrand new pittsburge compression tester from harbor freight for free. I figured what the hell I'll take it and tried it out on my saw. compression came in at 15PSI on a 40cc husky and 60PSI on a 7900. I know this is wrong as both the saws still rip with plents of pull. I'm pretty shure I'm missing the Schrader fitting to make this tool applicable to chainsaws. Can anyone post an adapter or connection peice to make this tester work on saws? Or should I just buy a new kit?

 

[Deleted member 117362]

So ive been given a nrand new pittsburge compression tester from harbor freight for free. I figured what the hell I'll take it and tried it out on my saw. compression came in at 15PSI on a 40cc husky and 60PSI on a 7900. I know this is wrong as both the saws still rip with plents of pull. I'm pretty shure I'm missing the Schrader fitting to make this tool applicable to chainsaws. Can anyone post an adapter or connection peice to make this tester work on saws? Or should I just buy a new kit?

Those adapters add volume to your cylinder top end and will give a very inaccurate readings.

 

[BJD85]

Those adapters add volume to your cylinder top end and will give a very inaccurate readings.

Thanks for the info duce good to know. Can you reccomend a good kit for chainsaws?

 

[Deleted member 117362]

Thanks for the info duce good to know. Can you reccomend a good kit for chainsaws?

You want a tester with valve in end of adapter.

 

[cuinrearview]

I have the same tester. No adapter needed. Mine works fine

 

[cuinrearview]

Just screw this in where the spark plug goes. Connect the gauge on the other end. Pull the saw over quickly until the needle stops rising.

 

[Deleted member 117362]

Just screw this in where the spark plug goes. Connect the gauge on the other end. Pull the saw over quickly until the needle stops rising.View attachment 765243

Is there a valve at end of hose, screwing into cylinder, is he having to use adapter screwed on first, then screwed into cylinder. Doses yours give same reading using an adapter? Looks like he was using 3rd adapter from top.

 

[cuinrearview]

Is there a valve at end of hose, screwing into cylinder, is he having to use adapter screwed on first, then screwed into cylinder. Doses yours give same reading using an adapter? Looks like he was using 3rd adapter from top.

Hose has a valve in the end. If he put an adapter on that would explain the low reading.

 

[BJD85]

I tried screwing it directly in got the same reading. There is no valve at end of the hose or in the connection peice. Getting 60 psi every wich way.

 

[BJD85]

I just found a vidio on this tester and posted it last a new topic for some reason could not add to this one. Its under COMPRESSION TESTER. rearveiw did you get yours at harbor freight? Maybe I just got a bum tester. It was free so im not too concerned but would like to figure it out.

 

[Yotaismygame]

I went through this same thing when I first got into saws. Took two testers back to HF because they “didn’t work”. Testers with valves in the gauge not the end of the hose do not work on small engines.

Two things: this has been covered several times before and the information is out there. Last compression readings are very overrated. I get varying results most of which don’t make sense and readings between testers could be as much as 15 psi different.

 

[BJD85]

This is it. Practically brand new too

 

[Yotaismygame]

The hose basically expands the combustion chamber by a lot which is why you’ll get a low reading. If the valve is in the bottom of the hose it’s different. Pick up a tester from most auto parts stores and double check for a valve in the hose.

 

[cuinrearview]

Mine is the same. From HF. IDK I've had no issue. And Yota I get what you're saying but if you only use one tester consistent results can be had for diagnostic purposes.

 

[BJD85]

The hose basically expands the combustion chamber by a lot which is why you’ll get a low reading. If the valve is in the bottom of the hose it’s different. Pick up a tester from most auto parts stores and double check for a valve in the hose.

Thanks man you always come through. YEAH I did a few searches and was getting close to this answer. Its hard rifling threw 1000 posts about compression testers when you get 100 thigs to do in a day and I know you good people will solve the problem in a minute. Lol. I guess that is a little selfish and your probably tired of the same **** over and over. I think I just need to learn how to use this search engin a little better. Thanks again man

 

[Yotaismygame]

Mine is the same. From HF. IDK I've had no issue. And Yota I get what you're saying but if you only use one tester consistent results can be had for diagnostic purposes.

Oh for sure. I have had testers go bad or break from dropping. Picked up one from a garage sale once which was the best one I ever had but curiosity got me and I picked up one of those small engine specific testers. For some reason that small engine tester always reads much lower.

No biggie on the searching. It’s time consuming that is for sure. I read a thread on here where a guy put a valve in the hose on one of those HF testers. Tried it myself but was not successful

 

[Vintage Engine Repairs]

Had an identical one and it was junk 25psi reading on a brand new saw and an old scored saw. Need shrader valve in the spark plug hole I did a post on it a while back. The new compression tester was expensive but worth it. New readings were 127 and 180 haha my new one has two shrader valves which I was impressed to see..

 

[Vintage Engine Repairs]

https://www.arboristsite.com/community/threads/compression-testers.335612/

 

[North by Northwest]

Absolutely require the Schrader valve attached as close as possible to end of the hose or fitting inserted into the spark plug hole . Other wise the volume of the squish area is being dramatically increased on a chainsaw application ! . P.S. Also I use liquid filled gauges , which are a little more expensive but last much longer and are a little more accurate initially and long term .

 

[s sidewall]

My Snap-on has the valve at the plug fitting. Only time I remove it is to change it out when it won't hold pressure anymore.

Steve Sidwell