G'day Musky.
Look to be a pretty good set. Reviewed my earlier cautionary post, the lowdown hole is the mounting for the missing pick up pipe.
When it comes to oilseals in general, like bearings, there are standard sizes which manufacturers will choose to achieve economies of scale. So, in the case of the mainshaft seal, the Oilseal size is defined by intended shaft diameter, hole size in the casting and finally the width of seal required to match the thickness of the casting. Any bearing supplier list should give a cross reference to commercially available substitutes for the real thing from these dimensions. Seals come in Metric and Imperial sizes, and also differ in the lip profile type and intended direction of shaft rotation. Most are a steel pressing, with the seal material moulded on.
But as always, there are exceptions, peculiar to makes and models. The original mainshaft seal looked like a resin impregnated fabric cup.
Crank seal is probably a special too, but along with the unique gearbox sprocket seal, widely available.
Hole on a handy seal type crankcase is 55.5mm/ 2 3/16". To add to Trev's know how, yes the slinger type drive sleeve is too big, at 46mm/ 1 13/16". This should closely match the crank hole in these slinger cases. Drive sleeve for seal type is smooth edged to run on the seal, and slightly smaller at 43mm/ 1 11/16". All dimensions taken from used parts to hand, measured with caliper and eye.
For those folks running early cases and oil entering the primary, worth checking your bitza has the correct drive sleeve.
An extra note for all you Plunger builders. Pay close attention to the integrity of the pick up pipe and its seal into the crankcase. I had one split at the right angle weld where it fits the case.....no scavenge, oil everywhere....fault took some finding and of course the whole motor is built around this pesky li'l bugger. The ball valve always seems to have very limited lift on these early models so a good clean out of carbonised oil is a must.
Cheers.
Swarfy.
