47mm Pop Up Piston Kit 1127-030-2007 Fits Stihl MS310

47mm pop-up piston kit that fits the Stihl MS310 chainsaw, in the place of piston 1127-030-2007; kit contents as shown in the photos. Measure the old piston to confirm the 47mm size before ordering. The domed crown reduces combustion chamber volume, which raises compression and tightens squish for more low-end pull; it does not promise more peak power. Measure squish with solder through the plug hole before running it, since cylinders vary, and remember that shimming the cylinder retards the port timing. For a straight repair, use the standard piston.

• 47MM POP-UP PISTON KIT - A raised-crown piston kit, as shown in the photos. It goes where piston 1127-030-2007 goes, with a domed top in place of the flat one.
• FITS STIHL MS310 - The 47mm bore saw. Measure your old piston with a micrometer before ordering to confirm the 47mm size.
• WHAT A RAISED CROWN DOES - The dome takes up combustion chamber space, so it raises the compression ratio and tightens squish, which gives more pull low down. It is not a guaranteed gain in peak power; on a stock cylinder a flat-top can make the stronger saw.
• MEASURE SQUISH BEFORE IT RUNS - Crush a piece of solder through the plug hole and measure it. Cylinders of the same number vary, so a dome that clears one may not clear another. Shimming the cylinder up to make room retards every port timing at once.
• ON ASSEMBLY - Use a ring compressor, fit the clips with their openings away from the slot, and pressure and vacuum test the crankcase. For a straight repair, the standard flat-top piston is the right part.