Finally, a new crankshaft.

I got some infoozyazm together this weekend and have made a new crankshaft. Its not finished yet but is well on its way. To my amazement it runs perfectly true and is better than the last one. I'm going to counterbalance it this time, not as much as a single cylinder engine would be, but a bit more than "balanced".

The new crankshaft

The other thing I have to do is make two new cylinder sleeves. The originals were creating too much compression and that is what I believe was contributary to the demise of the crankshaft. I've bought some Meehanite a dense cast iron which is wear and heat resistant. I need to increase the lip thickness to raise the cylinder heads and reduce the compression ratio. The only control I have over the point of ignition is by the compression ratio. Too much and pre-ignition reduces power, increases temperature and leads to component failure as I've experienced. Too little and the engine is difficult to start, runs poorly and wastes fuel. I'll increase the lip thickness by a millimetre, if it proves to be too much I can easily remove some of the material to increase compression again.

A new Central Crank Web and Big End Journals

On examination of the old assembly it appears the screw pin location hole was drilled and reamered on the p***. I don't know how I managed that, hence the resulting stress fracture. So, back to the drawing board to make a new one.

Jig set up for silver soldering the big end journals into place.

The new Central Web complete with Big End Journals

The journals are too long at the moment and will have to be cut to length to enable fitting between the front and rear crank webs.

I removed the shaft from the gear box because the bearing was lumpy, but it worked fine after I'd taken it out, so I cleaned it all up and noticed the shaft was bent. This could be the cause of the lumpyness, so shaft straightened and re-assembled into housing, it now works fine again.