I have yet to come across a saw that deviates from the standard 180+ excellent, 150 normal, 120 low (may be difficult to start).
Compression In Different Engines?
- Thread starter Vintage Engine Repairs
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At what point are they needing a rebuild, in your opinion?
IMO you can't tell that by compression alone. You really need to look at the piston. Once the machining grooves are gone your risk of cracking a piston goes up exponentially. Sometimes compression is still good when this happens.
Good point. When do you see a significant drop in power related to compression readings 135 PSI and lower or so?
Really depends on what you started with. I have had when new 200psi engines and as low as 140psi engines.
The other thing is many compression gauges are often garbage and give BS readings that are inaccurate and not repeatable. If you have an interest in it I would make sure to spend the money on a quality piece.
When I was running chainsaws daily I would re ring after a year as the power would start to go down. After two years I would relegate to spair duty.
Personally, I have never seen two compression gauges read the same thing.
I have a Snap On compression tester and a US Gauge that I made a tester with and they both read the same.
Snap on a little out of my league . But, I can pull it one time and tell you whether it is in good shape or not.
Pull one several hundred times a week and it comes to you.
My home made one.
Depends on where it started. 120-130 was normal 40 years ago for some. At the same time there were some wildcat jreds, Dolmars, and huskies that had 200 out of the box. And even today they range from 130-200 psi new. Certainly aren’t any hard fast rules about what saws in general should be
Hey mate, If it’s a saw I’d put new rings in at 140 and piston swap when it’s around 0.12- 0.14mm skirt to wall clearance that’s when slap becomes audible in these. I had asked Jerry this question a few years ago and found it to be spot on. Every time I heard slap I began to be able to estimate the clearance. I’d take the machine apart and measure it and be very close. What about you?
Husky workshop manuals are awesome, they give more specs than stihl.
Be careful if you ever have to work on a 592, 084, or 3120. You will get caught in an endless loop of replacing rings and pistons even though they are brand new.
How does one double zero?
Leakdown testers are free. It all depends on how you look at it.
TDC 150 psi of air in the spark plug hole as it was shut down last.
Add oil.
Do it again.
What did your ear tell you?
Do you honestly think I bought a leak tester at nine years old?
TDC 150 psi of air in the spark plug hole as it was shut down last.
Add oil.
Do it again.
What did your ear tell you?
Do you honestly think I bought a leak tester at nine years old?
It’s much more likely you spent your $ on weed and a bong at 9 years old
Hey mate, thanks for sharing!
Nope. Bought and sold minibikes or small Hondas 50 or 70cc.
Riding mini bikes stoned is dangerous.
Just get a pizza, some Doritos and chill.
I've seen low compression blamed for problems with chainsaws and other equipment when that was not the issue. I've seen some chainsaws start easily and cut good with 80 psi.
I've seen a few chainsaws that auto mechanics overhauled and they complained that the compression was lower after they rebuilt the saw. They were using their big dog fancy high dollar snap on or Mac automotive compression tested which was not reading the samll CC engine compression correctly.
Most often their saw had fuel issues.
I've seen a few chainsaws that auto mechanics overhauled and they complained that the compression was lower after they rebuilt the saw. They were using their big dog fancy high dollar snap on or Mac automotive compression tested which was not reading the samll CC engine compression correctly.
Most often their saw had fuel issues.
