Piston kit, 35mm, for Stihl FS91, FS94, KM94 and HL94 machines. Replaces Stihl part number 4149-030-2001, which Stihl has superseded to 4149-030-2012. Contents: piston, ring, wrist pin and circlips. The ring on its own is 4149-034-3005, 35mm by 1.2mm. The engine is a conventional single-cylinder two-stroke of 24.1cc, 35mm bore by 25mm stroke. There is no valve train and no valve clearance to set - if your machine has a rocker box on top of the cylinder, it is a 4-MIX and this is not the right part. Fits FS91, FS91R, FS94, FS94C, FS94R, FS94RC, HL91K, HL91KC, HL92C, HL92KC, HL94, HL94C, HL94K, HL94KC, KM94R and KM94RC, including the C-E and KC-E electric start variants. Piston kit only. Cylinder, needle bearing, gaskets and crankshaft seals are not included. Inspect the cylinder bore before assembly - scored or flaking plating will take a new piston down with it. And before you rebuild it, work out why it failed. On a trimmer this size a scored piston almost always follows an air leak or a lean carburetor setting rather than wear. Check the intake boot for cracks, pressure and vacuum test the crankcase, and fit a clean air filter. Otherwise the new piston goes the same way the old one did.
- 35MM PISTON KIT - Piston, ring, wrist pin and circlips. Replaces Stihl part number 4149-030-2001, which Stihl superseded to 4149-030-2012. Either number gets you here. The ring on its own is 4149-034-3005, 35mm by 1.2mm.
- FITS THE 24.1CC TWO-STROKE MACHINES - FS91, FS91R, FS94, FS94C, FS94R, FS94RC, HL91K, HL91KC, HL92C, HL92KC, HL94, HL94C, HL94K, HL94KC, KM94R and KM94RC, plus the C-E and KC-E electric start variants.
- THIS IS A CONVENTIONAL TWO-STROKE, NOT A 4-MIX - No valve train, no valve clearance to set, nothing in the crankcase to time. Stihl's own FS94 manual states it: single cylinder two-stroke, 24.1cc, 35mm bore, 25mm stroke. If your machine has a rocker box on the cylinder it is a different engine.
- PISTON KIT ONLY - Cylinder, needle bearing, gaskets and crankshaft seals are not included. Look down the bore before you fit a new piston. If the plating is scored or flaking, a piston alone will not fix the machine.
- WHY IT FAILED MATTERS MORE THAN THE PISTON - On a trimmer this size a scored piston usually follows an air leak or a lean carburetor setting rather than honest wear. Check the intake boot for cracks, pressure and vacuum test the crankcase, and fit a clean air filter before you run the new piston.