Compression Test?

I have two saws that I tested with this tester from Autozone.




My free Poulan Wildthing 42cc has 130 psi. I plan to put at least rings in it as a Dad son project.

My $50 028 Stihl pulls +150 psi by the 3rd pull, but as soon as I quit pulling it goes to 150 psi. If I don't release the pressure it drops slowly down to 120 psi. The saw runs, but seems to lack power. I have not done any vacuum testing of the saw. What do you think should be my next step with on my 028?

Carey

does it have the schraeder valve? i heard ones without will not give an accurate reading. they dont hold the pressure

+1

JONSEREDFAN6069 said:

does it have the schraeder valve? i heard ones without will not give an accurate reading. they dont hold the pressure

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Lots of diffrent reading frm what you get frm a regular auto comp. tester...

Yes it has a schraeder valve.

Either the schrader is leaking or it's the the gauge, hose, or bleeder. It's not the saw......454

Ring won't help the wild thing much, it's the bores that wear in them as they are not plated, just bare aluminium.

Try tightening the shraeder valve on the tester, some times they get loose. I find though the more pressure you put in the testers the faster they leak down. Like posted above, it has nothing to do with the saw though, it's not a leakdown test like is done on a 4 stroke to check the valve seats.

Is the next step with my 028 is to do a vacuum test on it?

yes.

fourfivefour said:

Either the schrader is leaking or it's the the gauge, hose, or bleeder. It's not the saw......454

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+1

Is 150 psi in the middle of the good range or on the low end for compression?

That's fine. Depends on the saw. Some go higher, some don't.

I have a saw with a broken starter housing. If I use an electric drill at low speed (using socket to turn crank) will this give me a false reading on the high side? Thanks

If it sounds about the same sort of speed as it does when you pull the starter, then just do it 3 or 4 times in quick succession - same way you would if starting the saw. It shouldn't give you any daft readings that way.

barneyrb said:

I have a saw with a broken starter housing. If I use an electric drill at low speed (using socket to turn crank) will this give me a false reading on the high side? Thanks

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dieselscout80 said:

Is 150 psi in the middle of the good range or on the low end for compression?

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150 psi compression is good, 100psi is the minimum amount you need to get the engine to run.
You didn't mention what size bar and chain you got on there.
I have a 16" bar with .325 full chisel chain on my 028 super (51.4cc's) and it rips.
If you don't have too big of bar and your saw is still lacking power, try a new fuel filter and spark plug. If that doesn't help get a kit for the carb and clean it out and retune your mixture. It should be fine after that.
Also depending on the model 028 you have it could be 43, 47, or 51.4 cc's....................454

PatrickIreland said:

If it sounds about the same sort of speed as it does when you pull the starter, then just do it 3 or 4 times in quick succession - same way you would if starting the saw. It shouldn't give you any daft readings that way.

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You can turn it over til the cows come home, it can only get so high and won`t get any higher by turning constantly.
Pioneerguy600

Time to jump into an old thread! My wildthing (2375) 42cc shows 175psi. Very little use since new, at least 20 tanks of gas and bar oil, (it oils big time), and 5 years (new fuel lines of course), to compare my neighbors new Poulan 4218 with 5 tanks of gas shows no more than 150psi. So yes a Wildthing can get high psi, it's still a POS but it won't die!

fourfivefour said:

Either the schrader is leaking or it's the the gauge, hose, or bleeder. It's not the saw......454

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I agree

Might want to check the date, thread is over a year old.

timberwolf said:

Might want to check the date, thread is over a year old.

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ya i know im trying to get my numbers up lol

timberwolf said:

Might want to check the date, thread is over a year old.

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I was reading away then seen Lake's post, I checked date of thread then





TT