In terms of design, Harley-Davidson cylinders are manufactured by casting and represent a single unit, a cylinder where the piston and the cylinder head are moving, and valve seats on intake and discharge sides are arranged in a unique way.
The design of early built Harley-Davidson cylinders includes a valve mechanism installed beside the blind-end cylinder, see Photo 1(A). Intake valve within the valve mechanism is installed in a separate enclosure in the cylinder head, see Photo 2(B), and discharge valve is installed deep inside the cylinder head body, see Photo 3 (C). In this arrangement intake and discharge valves travel towards each other during the operation.

In Photo 3, the valve seat working surface on discharge side before machining is marked with (C). Valve seat machining on discharge side installed deep inside the cylinder head body was performed using a NEWEN GII high-accuracy machine with an extension chuck and a profile form cutter. The deep-installed discharge seat machining process is shown in Photo 4.
The deep-installed discharge seat machining result is shown in Photo 5 (C1). For quality and reliable clamping of Harley-Davidson cylinder to the NEWEN GII machine an additional base part is provided. Valve mechanism on intake side has an original design solution. Enclosure with a valve installed in the operational location inside the cylinder is shown in Photo 2 (B). Intake valve unit has a removable enclosure. Therefore, shaping of working and auxiliary faces of the intake valve seat was performed using the NEWEN Epoc machine. Enclosure clamping on the NEWEN Epoc machine table and point cutting pattern shown in Photo 6 ensured quick and hight-quality performance. The second machining step included cylinder honing for an oversize piston. The allowance for honing is 1 mm.
Cylinder honing was performed on a Rottler НР7А honing machine. The machining diagram is shown in Photo 7. Cylinder honing was performed using a special device for honing of wet cylinder liners with production of an additional base part for clamping of the Harley-Davidson cylinder to be machined. The operation was performed to a good quality in line with the modern honing requirements, providing 82.00 mm diameter to a tolerance of +0.005 µm, surface roughness of 0.8 µm (0.6-1.0 µm tolerance for petrol), with not less than 20 % uncoated spherical flake graphite (obligatory brushing with hone brushes was performed).
Our Rottler НР7А, NEWEN GII, NEWEN Epoc equipment ensures high-quality machining of almost any ICE part, both modern and vintage.