New piston, cleaned cylinder, low compression?

[MS290man]

Hi guys, need some help. Got the new OEM piston for the MS271 that was straight gassed by PO. The cylinder cleaned up nice using the no acid technique and everything went back together well. Let the gasket sealer cure and did a pre-run compression check; 130 psi. Seemed low but I didn't freak. Put in some fresh gas and bar oil and gave her a pull. Coughed after 3rd pull on choke, backed off choke and she ran 2 pulls later. Blipped the throttle on and off for about 2 mins to let it warm until it dropped into a steady idle. Sounded nice. Shut it down, pulled the plug and re-ran the compression test. Still 130 psi?! I haven't cut anything yet (waiting for the bar and chain to come) but I woulda thought it would be better than that.

This is my first cylinder recovery; all the other saws where I replaced both cylinder and piston had higher compression cold (150+). Is that normal?

 

[dall]

what brand piston and rings ?

 

[MS290man]

OEM stihl

 

[huskihl]

Takes a couple tanks to let the rings seal

 

[Wagnerwerks]

Yeah. That's not unheard of for a new set. I'm not very familiar with the 271 bit I'd guess it's not a crazy high compression saw stock.

 

[Gypo Logger]

I'd lose the base gasket if you havent already, providing there is enough clearance. Maybe I should have read the whole post before I jumped in. Lol

 

[Lone Wolf]

Hi guys, need some help. Got the new OEM piston for the MS271 that was straight gassed by PO. The cylinder cleaned up nice using the no acid technique and everything went back together well. Let the gasket sealer cure and did a pre-run compression check; 130 psi. Seemed low but I didn't freak. Put in some fresh gas and bar oil and gave her a pull. Coughed after 3rd pull on choke, backed off choke and she ran 2 pulls later. Blipped the throttle on and off for about 2 mins to let it warm until it dropped into a steady idle. Sounded nice. Shut it down, pulled the plug and re-ran the compression test. Still 130 psi?! I haven't cut anything yet (waiting for the bar and chain to come) but I woulda thought it would be better than that.

This is my first cylinder recovery; all the other saws where I replaced both cylinder and piston had higher compression cold (150+). Is that normal?

Depends how old and worn the cyl was before you cleaned up the transfer. If it had lots of hours on it that would explain. Also it depends how well you cleaned it up. It prob will come up 5 lbs with break in of the rings . Nothing beats a new cyl OEM.

 

[USMC615]

Depends how old and worn the cyl was before you cleaned up the transfer. If it had lots of hours on it that would explain. Also deepens how well you cleaned it up. It prob will come up 5 lbs with break in of the rings .

Hey Steve...how ya doing brother?

 

[Lone Wolf]

Hey Steve...how ya doing brother?

OK man ,same old stuff. You Ok?

 

[USMC615]

OK man ,same old stuff. You Ok?

Doing good. Everything ok around these parts. Crazy damn weather here in mid-Ga, ain't complaining though. It's about 75 now, been in shorts, flip-flops since sunup this morning. Helluva winter ain't it?

 

[Lone Wolf]

Doing good. Everything ok around these parts. Crazy damn weather here in mid-Ga, ain't complaining though. It's about 75 now, been in shorts, flip-flops since sunup this morning. Helluva winter ain't it?

Mild winter here too. Better that way.

 

[USMC615]

Mild winter here too. Better that way.

Agree...tell Jimmy, Oly and all the crew in the big PM over on Ass Site I said hello and hope everyone is doing well, healthy and happy, for me brother.

 

[Lone Wolf]

Agree...tell Jimmy, Oly and all the crew in the big PM over on Ass Site I said hello and hope everyone is doing well, healthy and happy, for me brother.

Will do.

 

[Al Smith]

Keep in mind because of the design you have two types of compression reading .The first being "static" which is the standard test in a not running condition .

More important which you can't measure with normal methods is "dynamic " which can not be be measured using standard test equipment because the engine is in a running condition .

Besides it might take a good while to seat a new set of rings .It took me the best part of one summer on an 038 mag I rebuilt with new rings on a used cylinder .It now has a D-handle if that says anything .