Husqvarna 288 288XP 54mm Pop Up Piston Kit Ring 503506002

Raised-crown pop up piston kit for the Husqvarna 288 and 288XP chainsaws, 54mm bore, 87cc. Replaces Husqvarna part number 503506002, superseded to 544224102. Fits the 288, 288XP and 288XP Lite. CONTENTS. Piston, one compression ring, wrist pin and circlips. The 54mm piston for this saw takes a single ring. The cylinder is not included, and neither are gaskets or crankshaft seals. WHAT A POP UP PISTON IS. The crown is taller than a standard flat top, so it occupies more of the combustion chamber at top dead center. That raises the compression ratio. The same raised crown reduces the clearance between the piston and the cylinder head across the squish band. SQUISH HAS TO BE MEASURED. This is not a part to bolt in and run without checking. Crown height varies between production batches, so the clearance you end up with is yours to find, not a figure that can be published. The method is a length of soft solder laid across the squish band through the spark plug hole, the engine turned through top dead center by hand, and the crushed solder measured with a caliper. WHAT THE NUMBER TELLS YOU. Clearance that is too wide gives up most of the benefit of the raised crown. Clearance that is too tight risks the crown contacting the head. The cylinder base gasket is the normal adjustment: thinning or removing it tightens the squish and raises compression, but it also alters port timing, so treat it as a deliberate change rather than a shortcut. Machining the squish band in the head is the alternative. A FITMENT WARNING WORTH READING. The Husqvarna 281, 281XP and 181 are 80.7cc on a 52mm bore and use a different piston, with two rings, under a separate part number. Many sellers group 181, 281 and 288 on a single 54mm listing. They are not the same part. Confirm the bore or the model before ordering. BEFORE REASSEMBLY. A scored bore is a symptom. Pressure and vacuum test the crankcase and deal with a hardened crankshaft seal, a split impulse line or a loose intake boot first. Check ring end gap in this cylinder, use a ring compressor, and fit the circlips with the open end away from the ports.

• 54MM POP UP PISTON KIT FOR THE HUSQVARNA 288 AND 288XP - Piston, ring, wrist pin and circlips, replacing Husqvarna part number 503506002, which has since been superseded to 544224102. Fits the 288, the 288XP and the 288XP Lite, all 87cc at a 54mm bore.
• WHAT A POP UP PISTON ACTUALLY DOES - The crown stands taller than a flat top piston, so at top dead center it fills more of the combustion chamber. Less chamber volume means a higher compression ratio. It also means less clearance between the crown and the head, which is the squish band, and that is the part you have to measure.
• MEASURE SQUISH BEFORE YOU RUN IT - This is the one step that matters on a raised-crown piston. Lay soft solder across the squish band through the plug hole, turn the engine through top dead center by hand, and measure the crushed thickness. Crown height varies between production runs, so assume nothing and check your own.
• WHAT TO DO WITH THE NUMBER YOU GET - Too wide and the raised crown gains you little. Too tight and the piston can touch the head. The base gasket is the usual adjustment, and thinning or deleting it tightens squish - but it also shifts port timing, so it is a change to make deliberately. Cutting the squish band is the other route.
• 54MM ONLY - DO NOT FIT THIS TO A 281 OR A 181 - Those saws are 80.7cc on a 52mm bore and they take a different, two-ring piston under a different part number. Plenty of sellers list 181, 281 and 288 together on one 54mm kit. Measure your bore, or read the model plate. Piston, ring, pin and clips only - no cylinder, no gaskets.