- (1) I think this problem lies mainly in the size of the inlet valve, I have designed it too big and too much mixture is getting into the cylinders and compression reaches the point of ignition too soon before top dead centre (TDC). If it were a spark ignition engine I could control the point at which ignition takes place, but this is a glow plug engine or semi-diesel and ignition is controlled by the amount of compression. I fitted restrictors in the cylinder heads to reduce the gas flow into the combustion chamber. This has helped but there are other things to be done. I may have to look at the valve timing.
- (2) I was hoping the crank case would breathe through the front bearing and to some extent it does, but its not enough so I've incorporated a breather nipple to replace one of the gearbox retaining screws. I had to drill the existing tapped hole in the crank case through to allow the pressure to release.
You can see where the crack started to form around the outside and worked its way to the centre. Click on the photo and it should enlarge.
My first job is to retrieve the gear and bearing from the rear part of the shaft. Its probably best to drill the shaft out of the gear and do the same for the bearing. It's a good thing I've got plenty of stock material left over.