{"product_id":"husqvarna-371-372-xp-pop-up-piston-50mm-non-x-torq-14-kj1f-0ygn","title":"50mm Pop Up Piston Kit Fits Husqvarna 371XP 372XP 1.5mm Ring","description":"\u003cp\u003ePop-up piston kit that fits the earlier Husqvarna 371XP and 372XP, 50mm. A raised-crown 50mm piston for the saws with the 1.5mm ring. Supplied with rings, piston pin and circlips. WHAT A POP-UP PISTON DOES The raised crown reduces combustion chamber volume, which raises the compression ratio and tightens squish. The result is more torque low down and easier starting. It does not reliably add peak power - builders running a pop-up and a flat-top on the same stock cylinder often report the flat-top made the stronger saw, because the dome disrupts charge flow across the crown. EARLIER SAWS ONLY Both versions of this saw are 50mm, so bore is useless as a test. The ring thickness settles it: 50 x 1.5mm is the earlier engine and takes this piston, 50 x 1.2mm is the later XT engine and does not. An XT in the model name on the plate is the other check. This piston does not fit the earlier 365, which is a 48mm saw. SQUISH MUST BE MEASURED Crush solder through the spark plug hole at four points around the piston, rotate the engine slowly through top dead centre by hand, and measure the flattened solder. Re-measure once the piston is fitted, with the base gasket in place. Shimming the base to clear the dome retards every port timing figure at once and hands back what the compression gained, so it is not the fix. IF YOU WANT A STRAIGHT REPAIR The standard flat-top piston is the part for a saw that simply needs a piston, and it is the better choice for most rebuilds.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eRAISED-CROWN 50MM PISTON FOR THE EARLIER 371XP AND 372XP - Supplied with rings, piston pin and circlips. The raised crown reduces combustion chamber volume, which raises the compression ratio and tightens squish. It is a part for a measured build, not a drop-in replacement, and the standard flat-top piston is the right part if you want a straight repair.\u003c\/li\u003e\n\u003cli\u003eWHAT A POP-UP ACTUALLY DOES - More torque low down and easier starting, from the higher compression. What it does not reliably do is add peak power: builders running both on a stock cylinder often find the flat-top made the stronger saw, because the dome disrupts charge flow over the crown. That is the honest picture, and it is why this page does not claim a power gain.\u003c\/li\u003e\n\u003cli\u003eEARLIER SAWS ONLY, AND THE RING TELLS YOU WHICH YOU HAVE - Both generations are 50mm, so a caliper cannot separate them. The ring can: a 50 x 1.5mm ring means the earlier engine, which is this piston, and a 50 x 1.2mm ring means the later XT engine, which takes a different one. An XT in the model name on the plate also settles it. This does not fit the earlier 365, which is a 48mm saw.\u003c\/li\u003e\n\u003cli\u003eSQUISH MUST BE MEASURED, NOT ASSUMED - Crush solder through the spark plug hole at four points around the piston perimeter, rotate the engine slowly through top dead centre by hand, then measure the flattened solder. Re-measure after the pop-up is fitted with the base gasket still in place. Cylinders carrying the same part number vary enough that this cannot be skipped.\u003c\/li\u003e\n\u003cli\u003eDO NOT JUST SHIM IT TO CLEAR THE DOME - Adding base gasket thickness to buy clearance retards every port timing figure at once, which hands back the power the compression gained. If the dome will not clear, the answer is to cut the squish band or choose the flat-top piston, not to pack the base. Check ring end gap in the bore the rings will run in before assembly.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Lil Red Barn","offers":[{"title":"Default Title","offer_id":68009605464218,"sku":"14-KJ1F-0YGN","price":34.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0397\/2346\/6909\/files\/71oePfHrGAL.jpg?v=1793382491","url":"https:\/\/performancesawsupply.com\/products\/husqvarna-371-372-xp-pop-up-piston-50mm-non-x-torq-14-kj1f-0ygn","provider":"Performance Saw Supply","version":"1.0","type":"link"}