As we keep moving around the magnesium case, we are ready to re-install the oil breather plate. This cover is prone to warping over time, heat cycling, and overtightening. As well, the case machine work often leads to this part not fitting any more.
We have a solution to all these problems! You will have your oil breather cover installed in no time.
Testing your Oil Breather plate
Try to place your oil breather plate over the studs on your magnesium case. Please don’t force it! If your case has been closed and honed, the cover may not fit.
To solve the problem, we are going to ream the holes in the lid. The hole size is around 6.5 mm and we are going to ream it out to 7mm.
We do this simply, by using the existing oil breather plate holes. Using a quality drill bit we drill through the existing hole. The wood makes for a easy exit for the drill.
When you drill these holes out you will create a snag of metal around the base. It is all good because we need to sand the gasket surface anyway.
Tools we used
Sanding your Oil Breather Plate
Set yourself up with a piece of glass and 60 grit sandpaper like we do, or use a sanding machine if you have it. Do a quick pass to knock off the drill marks, then take a look at the high points.
We continue in a figure-eight pattern until the high points start to fade. There was a little corrosion in the magnesium, so we continued sanding.
The cover uses 6mm hardware, and again we choose to replace the original set up with a flat washer and a Nylock nut.
The 6mm nuts should be torqued to 6 Newton Meters.
Engine hook and oil fitting.
You can go ahead and install the oil pressure sender adaptor plug while you are right here. Install the copper sealing ring and torque this to 42 Nm.
Now is the time to put on the engine lifting hook and torque down that 8mm nut to 25Nm.
Up Next in your Air-Cooled Engine Build
Now that your oil breather plate is on, you can stay on this side of the engine. The oil thermostat is right here and you can continue with your build. In our next lesson, we show you how to test and install the oil thermostat, along with some more oil fittings!