Leading Edge 125" and 129" M8 Top End Kits


Leading Edge


Leading Edge V-Twin was born from Nascar and Trophy truck racing and since the brand has evolved into being at the forefront of premium engine performance for Harley-Davidson motorcycles. Coming off the success of the monumental 151ci kit for Harley-Davidson Milwaukee Eight, Leading Edge is proud to announce the release of its 125ci and 129ci bolt-on top end kits for air and twin-cooled 2017-2019 H-D M8 models. This top end kit is now the largest “bolt-on” kit for 107ci and 114ci motors in the world. This kit works well with a wide range of aftermarket cams and does not require machining of the engine crank cases. All of our kits have been extensively tested both in-house on our Dynojet dyno and on the road in and around Phoenix, Arizona, the Smoky mountains of Tennessee, and Southern California in real-world riding conditions to insure nothing but massive amounts of dependable horsepower for your hard earned money.


We don’t re-use stock over-bored cylinders or buy cylinder blanks made overseas. Each of our unforgettable cylinders are made one-by-one on a Haas 5th axis CNC machine in the USA out of 41-pound American-sourced and made billet aluminum blocks. Our proprietary house-made cylinders were designed using aerospace techniques usually reserved for military applications. This “grooved and faceted” design along with the material used in manufacturing them has shown time and time again to dissipate heat better than the old multi-finned design found on most motorcycle cylinders. 


The custom-designed 11:1 compression ratio pistons are specially dished to offer the most performance. The pistons also feature valve reliefs and are forged and machined right here in the USA


LE’s 125 kit is available for the 2017-2019 H-D Milwaukee-Eight 107ci engines (air cooled & twin cooled)


LE’s 129 kit is available for the 2017-2019 114ci & 117ci Milwaukee-Eight engines


Each of the 125ci and 129ci kits from LE comes complete with pistons, piston rings, and of course Leading Edge’s unforgettable CNC-machined “Grooved and Faceted” cylinders. All needed gaskets and hardware are included with each kit 


Kits are available in our remarkable “as-machined” finish. Custom colors and finishes are also available singularly as special orders.