Predator 224cc
Internal Upgrades

Stock is a cast, dished 70mm piston — the same non-Hemi dish style as the 212, just larger in bore. Since 212/GX200 pistons measure 68mm, they don't fit; forged replacements need to be sized for the 224's actual 70mm bore. Flat-top forged pistons raise compression and, as a side benefit, commonly use the standard .709" pin — which is what lets you run an off-the-shelf GX200-pattern rod instead of a 224-specific one. Match your final compression target to your head and fuel plan before ordering.

Here's the one that catches people out: a standard GX200/212 cam can physically interfere with the 224's case, because the 224's center main section is narrower to make room for the 58mm-stroke rod swing. Cam makers now grind 224-specific cores — the same duration and lift families as the familiar 212 cams, just reground with narrower lobes for clearance — or sell the standard cam pre-clearanced. Either way, never drop a generic 212 cam into a 224 and assume it fits; verify rod-to-cam clearance before first start, every time.

Stock springs are rated around 10.8 lbs and start to float near 5,500 RPM — fine for a governed engine, not for a cammed one. The 224 keeps the same 27mm/25mm valve sizes and 5.5mm stem as the 212, so standard GX200/clone spring kits fit physically. You can go up to roughly 26 lbs without machining the valve pockets; past that, budget for pocket work. Install fresh retainers and locks with any spring swap — don't reuse stretched stock hardware.

The stock head is the same non-Hemi family used on the 212, so it bolts up the same way and responds to the same treatment. Options: (1) port and polish the stock head — open up the intake and exhaust ports, clean up casting flaws, blend the seats. (2) Step up to an aftermarket aluminum race head, some offered with a lighter 5mm valve stem instead of the stock 5.5mm to trim reciprocating mass. Either route is worth several HP once your cam and compression can actually use the extra flow.

Good news after two case-specific sections: the flywheel is a straight bolt-on. The 224 uses the same taper, keyway, and bolt pattern as the wider Honda/clone family, so the same billet flywheels sold for the 212 and GX200 fit directly — no special 224 version needed. It's still not optional: the stock cast flywheel is a documented failure risk above roughly 5,500 RPM. Set timing to 28–32° BTDC for most performance builds.