Pop-up piston kit, 47mm, for the Stihl MS311 and MS362. Replaces 1140-030-2002, since superseded to 1140-030-2009. Contents: piston with a raised crown, ring, wrist pin and circlips. The domed crown sits closer to the cylinder head at top dead center, which tightens the squish band and raises compression; it is an aftermarket part, and 1140-030-2002 is the standard factory number it replaces. The MS311 and MS362 share a piston: both are 59.0cc, 47mm bore, 34mm stroke. The MS391 is 64.1cc on a 49mm bore and takes 1140-030-2003; some catalogs list it against 1140-030-2002 and they are wrong. Aftermarket 49mm big bore cylinders are sold to convert an MS311, but a stock MS311 is 47mm. Measure squish on assembly with a solder test through the plug hole and pick base gasket thickness from what you read. Raising compression raises combustion temperature, so set the high-speed mixture a little rich and take the first tank gently. Piston kit only: cylinder, needle bearing, gaskets and crankshaft seals are not included.
- POP UP PISTON KIT, 47MM - Piston with a raised crown, ring, wrist pin and circlips. The dome tightens squish clearance and raises compression. An aftermarket part; 1140-030-2002 is the standard factory piston it replaces.
- MS311 AND MS362 ARE BOTH 47MM - Both are 59.0cc on a 47mm bore with a 34mm stroke, so they share this piston. Replaces 1140-030-2002, since superseded to 1140-030-2009, so either number gets you here.
- THE MS391 IS NOT THIS PART - The MS391 is 64.1cc on a 49mm bore and takes 1140-030-2003. Same series, same stroke, 2mm more bore. Some catalogs list the MS391 against this number and they are wrong.
- BEWARE THE BIG BORE KITS - 49mm cylinder kits are sold to convert an MS311, which is why MS311 and 49mm turn up together. A stock MS311 is 47mm. If you have not fitted a big bore cylinder, 47mm is your size.
- MEASURE YOUR SQUISH ON ASSEMBLY - Check it with a solder test through the plug hole and choose base gasket thickness from what you measure. Too tight and the dome contacts the head. Richen the high-speed setting slightly and take the first tank gently. Cylinder, needle bearing, gaskets and crank seals are not included.