Pop-up piston kit for the Stihl MS261 and MS271. Bore 44.7mm. Replaces Stihl 1141-030-2012. SPECIFICATION Bore - 44.7mm Stroke - 32mm Displacement - 50.2cc Wrist pin - 10 x 6 x 32mm THE CHECK THAT MATTERS - WRIST PIN LENGTH. Stihl built the MS271 in two types and the difference is the pin: Type 1 - piston 1141-030-2012 - pin 10x6x32mm - cylinder 1141-020-1203 - THIS PISTON Type 2 - piston 1141-030-2003 - pin 10x6x35mm - cylinder 1141-020-1204 Measure the pin out of your old piston. Three millimeters is the entire difference and no photo will show it. THE MS261. Stihl's current MS261 piston number is 1141-030-2031, and this piston is cross-referenced to it. The MS261 also went through a cylinder change, straight fin to slant fin; this piston covers both. SAME ENGINE SIZE, DIFFERENT SAWS. The MS261 and MS271 share bore, stroke and displacement, which is why one piston fits both. They are not otherwise the same machine - the MS261 is the professional saw with a magnesium case, the MS271 is the Farm Boss. WHAT A POP-UP PISTON IS. The crown is raised so it projects further into the combustion chamber at top dead centre, reducing chamber volume and raising compression. This is a performance variant. Stihl's own piston is flat topped. MEASURE SQUISH BEFORE YOU RUN IT. A raised dome consumes squish clearance. If the base gasket has also been deleted the two changes stack and the crown can contact the head. Check with a length of solder through the plug hole before final assembly.
- FITS THE MS261 AND MS271 - 44.7mm bore, 32mm stroke, 50.2cc. Replaces Stihl 1141-030-2012. Both saws are dimensionally the same engine, which is why one piston covers them, but they are not the same saw - the MS261 is the professional magnesium-case version and the MS271 is the Farm Boss.
- CHECK YOUR WRIST PIN LENGTH - THIS IS THE 32mm PISTON - Stihl built the MS271 in two types. Type 1 takes piston 1141-030-2012 with a 10x6x32mm pin, which is this one. Type 2 takes 1141-030-2003 with a longer 10x6x35mm pin. Measure the pin out of your old piston before ordering. Three millimeters is the whole difference and it is not visible in a photograph.
- THE MS261 HAS ITS OWN TWO VERSIONS - straight fin and slant fin cylinders. This piston is cross-referenced to both, and Stihl's current MS261 number is 1141-030-2031. If your parts diagram shows 2031, this piston covers that application.
- RAISED DOME, NOT THE STOCK FLAT TOP - The crown projects further into the combustion chamber at top dead centre, which raises compression. Stihl does not make a pop-up piston; the factory part is flat topped. Measure squish clearance with solder before you run it, and do not delete the base gasket as well - the two changes stack and the crown can reach the head.
- BEFORE YOU FIT A PISTON ALONE - Take the muffler off and look at the cylinder through the exhaust port. Light straw transfer will hone out. Deep vertical scoring or lifted plating means the cylinder is finished. And find out why it scored - a lean condition from an air leak or a worn seal will take the new piston the same way.