stihl 041 with 205lbs compression?

[pops21]

I'm rebuilding my 041. I pulled the cylinder over sand paper on a peice of glass while rotating it and got the squish down to .019 from .031. Well before I sealed it up I put the cylinder on the saw to see what the compression was. Before I put the cylinder on I lightly oiled the cylinder with some stihl ultra. After sever pulls of the cord it read 205lbs. Is this too much?

Its actually got a stihl 031 piston ring in it. I broke the original 041 ring pulling it off the piston to measure it in the bore. I had 4 031 used rings laying around. 041 ring was 44mm x1.5mm 031 ring was 44mm x 1.5mm. Ring end gap on the best 031 ring I had was .011" so I used it.

 

[Kenskip1]

Compression

Sir, this is a false reading.The oil that you used will not compress and this is giving you false information. I would look for something around 150 psi. If you really did have this much pressure you would have to put in a decompression valve. I may be wrong here but I doubt it,best of luck, Ken

 

[pops21]

Thats what I was kinda thinking. When I got the saw it had 155lbs of compression. So it should be more the 155lbs. I'm thinking all said and done it should be around 180+

 

[redunshee]

Sir, this is a false reading.The oil that you used will not compress and this is giving you false information. I would look for something around 150 psi. If you really did have this much pressure you would have to put in a decompression valve. I may be wrong here but I doubt it,best of luck, Ken

+1. Squirting oil in the cylinder will temporarily boost compression. If you stayabove 150-155 you're in great shape.

 

[spudulike]

Most compression I have had on a non modded saw is 175psi which is pretty good - 150psi is normal to good.

Once you run the saw up, the oil will burn off quickly - measure compression after you have run it for 15 seconds - it will probably have fallen significantly

Spud

 

[blsnelling]

After you run it, I'd be surprised if it's over 165.

 

[AUSSIE1]

Oiling the bore will give a higher reading.
Your comp will start to come back up some as the ring wears in.
Give it run for a while, let it sit overnight and retest.

 

[pops21]

Well I let it run for a few min last night. I blipped the throttle a few times to clear it out too. After the saw sat for 2 hour to cool I did another compression test. It pulled 200lbs of comp.. Then today I got to run it in some wood. Man does it pull a 20" bar NICE and its still pig rich 4 stroking in and out while cutting.:rockn: I am at work now, so tonight after work I will pull another comp test too see where its at. Stay tuned.

BTW this saw has new
crankbearings/seals
oil pump seals
every gasket
major rebuild carb kit

 

[pops21]

Update

Well I checked the compression. Its just a tad over 200psi. I also port matched the exhaust, intake and gaskets to the cylinder.

I think I'm gonna name her fat bottom girl.:greenchainsaw: I put the 25 inch duromatic with a woodland pro 3/8 .050 semi chisel for the pics. It will wear the 20 inch with the WP round chisel for most work.

 

[raybow1]

Wow I haven't seen that kinda compression before in a 041. If you know of anyone else with a comp tester maybe check it with theirs. Sometimes there is a big variance in compression testers. That's awsome!

 

[pops21]

My stihl 031 reads 155psi. I checked both at the same time. Just didn't take a pic of the 031

 

[stingray bay]

Well I checked the compression. Its just a tad over 200psi. I also port matched the exhaust, intake and gaskets to the cylinder.

Is that hot or cold? On my 880 there is about 20psi difference (155 vs 175) which I understand is pretty normal. I am guessing you want to know the compression is good hot as this is what the saw is actually running in the cut.

 

[pops21]

Thats cold. With about half a tank ran threw it.

 

[stingray bay]

Thats cold. With about half a tank ran threw it.

What does that drop to hot? I wonder if you will have a problem with detonation at that compression (In NZ we got rid of Leaded Gas a while ago)
Regards

Mark

 

[pops21]

Next time I run it I will check. I don't think it will be a problem. I think its 94 ocatan that I'm running in it. My dolmar 5100s is at 200psi and it runs fine.

 

[Rudedog]

Should compression be tested hot or cold? I always thought it should be tested once the saw hit operating temperature. I am new to compression testing having just bought one from Baileys.

 

[spudulike]

I do all mine cold just so I have a benchmark, a saw will drop compression when warm just through expansion and the oil in the fuel thinning, if a saw is being troublesome when warm and the compression is down when warm then it is time to do some work on the top end but it will usually show when cold as well.

I usually look for 140psi + when cold - close to 100psi on the first pull - only exception to this has been my Poulans - low at 130-135psi cold but from this site - appears normal!

Spud

 

[pops21]

Video

Well here is a video I took today. It was 92 deg. F and pretty humid. I just threw my coveralls and PPE on to make the quick video and was pouring the sweet. That is a 25" hard nose duromatic bar with a new semi chisel woodland pro chain. It runs like a top. Only bogs a little when I dig in but still keeps trucking. I'm trying to keep it on the rich side for the next few tanks. ENJOY
The saw was also warmed up before I made the first cut in this vid.

<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid158.photobucket.com%2Falbums%2Ft120%2Fbhdpops21%2FMVI_1894.mp4">

 

[spudulike]

sounds fine - what is the compression cold/warm now?

Spud

 

[pops21]

I was in a hurry. I had 30 min to be at work when i got finshed cutting. Then it took me 10 min to start loading it on photobucket. Its not really to impressive with the semi chisel chain. But thats why I got that chain for the 25" bar. Since its not as agressive as a full chisel chain it won't bog down as bad. Plus Thats my set up for dirty skided timber at the mill. Next I will post some vid with the 20" bar and the full chisel chain. It should be this weekend sometime.