Can't let this compression issue die

[daveb]

compression readings

You guys got me curious and I just couldn't leave it alone, so here are my results-cold and WOT with snap-on gauge-
028 super- 145
038 magnum- 145
shin 695- 160
351- 160
372xp- 150
288xp well used-135

 

[stihltech]

weight

I have not found the extra weight of a bar makes any difference, however, I would not pick up a saw with over a 24 inch bar this way anyways. As for old saws, it is the quickest way as most of my customers do not want to spend any amount of money on them. If it will involve going inside, it is done.
Like I said, works for me, save time.

 

[HUSKYMAN]

If it runs good, starts good and has balls, it has good compression

If it is hard to start and smokes it doesnt.

Isn't that good enough

 

[treeclimber165]

methinks BIG just needs a hobby.

 

[BIG]

I have a hobby - playing with these saws

Treeclimber165, I believe you miss the point of this discussion and forum entirely (just my opinion). I do have a hobby, several of them, and playing with and understanding these saw we discuss on this forum is one of them. Does this not qualify for you? Sorry to "bog" you with my posts. If they offend you, don't read them and certainly don't reply to them. No offense intended here but remarks such as yours add nothing to a post such as mine.

 

[Newfie]

Well, if there's nothing wrong with the saw I bet most are willing to let this compression issue die. Maybe your hobby should include some tech manuals for your saws. That could be a new sub-hobby, tracking down the manuals so you poke and prod and test the saw.

I'm with Treeclimber and Huskyman on this one.

 

[treeclimber165]

Perhaps my last post was a little brash. I apologize if I made you feel bad.

Point is, you have consistent readings with several different engines. The number is irrelevent. Obviously your gauge reads low, but you can still use it since you have a baseline to start from. If you used Daveb's gauge, you'd probably get numbers in the 145-160 range.

I think this horse has been kicked to death. If you want to see 150 readings, buy a better gauge. Or adjust the numbers on yours.

 

[Greg Carberry]

I will second BIG in this is part of the hobby for me as well Nothing wrong with testing your compression. I do with everything I have I use a Sears Craftsman guage I bought several yrs ago. It has the removable hose. If you want a good guage you can really use get the kind with the hose that threads in. Seals much better than the push it types. My old saws and most every other 2 cycle equipment I have are getting 140-150. You know too that the guage is right when they pass the hang test too.

 

[stihltech]

compression

SUMMARY
Some of us feel a compression test with a guage is needed, some don't.

END

 

[daveb]

Originally posted by Pioneer
You know too that the guage is right when they pass the hang test too.

All of my saws pass the hang test except the 288xp which showed low compared to the others, but it is also one HEAVY saw. It still starts good and has power, so I guess it can't be too bad.

 

[Dennis]

My Super 930 Jonsered passes no hang test, nor does my 272...but I dare ya to beat them in a race....loser buys...bring money...

 

[dbabcock]

Can I bring my 3120?

 

[WRW]

I'm not taking sides, honest. I just wonder how much mechanical advantage can be obtained from any single fixed pulley.
Since crankcase pressure is paradoxical to cylinder pressure, how would a hang test be affected by low crankcase pressures?

 

[dbabcock]

"Paradoxical"?

 

[WRW]

Yeah, well, it's not exactly opposite. Independant? Different? If you've ever seen a flail chest...well ...now I got visions of that gal runnin'. Where was I?

 

[stihltech]

?

Now I am in a paradox.

 

[Dennis]

I hate it when you guys talk about things I cannot pronounce...

 

[stihltech]

comp

OK, I use the hang test religeously, but that is only the start. Make sure the plug is tight (I find a lot of those). Check the spark and fuel, then pull the muffler. If I have any question, the bearings are getting checked and the cylinder is coming off. I don't run into too many wher the compression is down "a little". It usuall hangs or pulls the rope out quite rapidly. I just find it to be a quick diagnostic tool in the everyday world of saw repair. I am sure the hop up guys will see it different, but they are going for a different result than I am.

 

[dstaton]

All this discussion on compression, but none I can find relating to piston ring blow by. In a 2 cycle it would seem to be a critical event. Blow by would be quite detrimental to proper engine function. How do the various saw manufacturers overcome this?

 

[tundraotto]

this is what they are measuring by the tests....