Pressing Times!

Our Allen gets himself pressed into action to sort out his crankshaft.

- Allen Millyard

The disassembly and assembly of a pressed up multi-cylinder crankshaft is considered by many to be a specialist job, carried out behind closed doors with mystique and intrigue, but it’s actually quite an easy job to do at home if you have a few bits of basic engineering equipment.

With the crankcases finished, it was time to start adapting a standard four-cylinder Z1 crankshaft to fit my new six-cylinder engine. The standard Z1 crankshaft is a pressed up design made from eight hardened steel webs and a central shaft containing the cam-chain drive sprocket. The webs vary in shape and purpose. One web incorporates the primary drive gear; four webs incorporate big-end journals; and the other four webs incorporate the main bearing journals. There are six roller bearings that run directly on the hardened main journals and the hardened outer rings of the roller bearings locate in the crankcases with pegs to align oil feed holes.

The first job I had to do was to strip down two Z1 crankshafts and I was expecting some trouble! I remembered the force required to strip a Z1 crankshaft when I was making my Kawasaki Z1600 V8 over 20 years ago, it stretched the limits of my hydraulic press and I wasn’t looking forward to it. The first thing I had to do was make a couple of support bars from high tensile steel that fit between the webs, making them as thick as possible to take the load required to press the crank-pins and journals from the webs. I had a length of 30mm square EN16 steel bar that was ideal, so I cut off two bits about a foot long, but they would need reducing to 23mm thick in the centre using my milling machine, so that they would fit in the gap between the webs.