Stihl 251C easy2start low compression

[Backtroller]

Hello, first post since I discovered this site. I picked up a stihl 251c with easy2start for what I thought was a good deal. It starts on the first pull and sounds healthy, but when I checked the compression it was 115 psi. I have used the same gauge on my other saws and see 155-165. The only difference is that this saw has the small 10mm spark plug and I used the adapter with the actron tester. When I pulled the muffler the piston is not shiny and smooth like my other saws. It has "ribs" on the piston skirt from the factory. There is some staining (carbon?) in these grooves but no scratches or gouges.

Never worked on new low emissions saws and it is difficult to get a feeling for the compression with the pull start. Anyone try checking a saw such as this? I have not checked compression hot. Am I worried for no reason?
Thanks

 

[blsnelling]

Post up a pic of your piston.

 

[Backtroller]

I'm going to have to figure out how to do that on this site

 

[Backtroller]

 

[Backtroller]

 

[Backtroller]

Sorry those are the best pictures I can get right now.

 

[sunfish]

It's probably fine. The low reading is likely from the adapter.

 

[Rockjock]

Hello, first post since I discovered this site. I picked up a stihl 251c with easy2start for what I thought was a good deal. It starts on the first pull and sounds healthy, but when I checked the compression it was 115 psi. I have used the same gauge on my other saws and see 155-165. The only difference is that this saw has the small 10mm spark plug and I used the adapter with the actron tester. When I pulled the muffler the piston is not shiny and smooth like my other saws. It has "ribs" on the piston skirt from the factory. There is some staining (carbon?) in these grooves but no scratches or gouges.

Never worked on new low emissions saws and it is difficult to get a feeling for the compression with the pull start. Anyone try checking a saw such as this? I have not checked compression hot. Am I worried for no reason?
Thanks

I agree with Sunfish, it maybe the adapter that is giving you the wrong readings. If it runs well and is fine in the cut then I think you will be fine. I have seen pistons like that it is it just some carbon/oil to be sure you can dip a long q-tip in mix or carb cleaner and gently wipe the surface I think you will find it just wipes off.

Welcome to the madness we call CAD.

 

[AKDoug]

I can almost guarantee that it's the compression gauge. Personally, I believe people put way to much stock in compression on this site. I far prefer a visual check on the cylinder. In my Stihl training classes we don't even use a compression gauge and it's not even on the Stihl engine check list.

 

[Backtroller]

Thanks everyone for the quick replies and valuable insight. I'm going go get a new bar and put it to use.

I'm in the process of reading past posts and would like to have a woods port done on my 026pro. Looks like this is a great site for that