Chapter 1
Description of the Engine, Its Systems, and Essential Technical Data
1.1 Overview
1.1.1 Model 2704
The Hirth 2704 engine (Illus. 1.1.1-1) from Göbler-Hirth Engines Ltd., is a fan-cooled, side-
regulated, two-cylinder inline, two-stroke engine.
The cylinders consist of an aluminium alloy coated with an abrasion-resistant surface. The
cylinders are attached to the crankcase with bolts, washers and hexagonal nuts. The cylinder
heads consist of a special non-melting aluminium alloy, which resists high temperature with
an even hardness. They are fastened to the cylinder without any sealant, using cylinder bolts
and washers.
The pistons consist of an aluminium alloy and are packed with two piston rings against the
cylinder surface. The piston is connected to a piston rod with a gudgeoned pin and needle
roller bearing.
The crankshaft is made of Chromoly steel (42CrMo4) and is positioned in five grooved ball
bearings. It is a constructed crankshaft in which the individual parts are pressed together to
form the complete crankshaft. Two grooved ball bearings are attached on the power take off
side, two more between the crank control handle, and one on the ignition side. The power take
off is cone-shaped and has a centric coil in order to wind a connecting cone onto the power
take off side. The piston rods are connected to the crankshaft with crank pins and needle roller
bearings.
The crankcase consists of an aluminium alloy. It is constructed as an axial divided case and
consists of a lower and an upper part. It is held together by three cylinder bolts with safety
washers, and in addition by the eight fastening bolts of the cylinders. On the ignition side, it
includes the stator plate of the ignition and is constructed so that the fan housing can be
mounted over it.
Illustration 1.1.1-1 (Engine 2704 two carburettor)
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