Mystery oil leak in back of 40 hp motor

[vwoldbug]

Can you look for a small rust hole in the oil filler .

[KTPhil]

Those low profile air cleaners do not give space for the fuel fog above the carb at certain rpms. It can wet the filter element, and even draw oil in from the breather to saturate it, and then it leaks down. Do you have a stock air cleaner you can try substituting? The internal tube acts to hold the fog, and of course it doesn't mind getting oil in its fibers.

[pdb27]

I do have a stock oil cleaner, but it's currently not usable because the breather hose opening on the right hand side has been pinched shut. There is a "Volkstoberfest" in Indy on 9 Oct that includes a parts swap, so I'll see if I can't score one when I'm down there. Several threads have recommended using the stock cleaner, and I think it will even help out with my crankshaft pulley leakage, so I'm planning to make that move.

[pdb27]

One more update to this thread after getting to know the motor for about 12,000 miles, and after attending several VW shows and speaking with old-timer mechanics possessing enjoyable esoteric knowledge about air-cooled engines.

First, there is likely something going on internally with the old 40-horse that is contributing to the oil seepage past the crankshaft pulley. I have noticed an omni-present ticking in the motor, even after adjusting the valves, and it is coming from inside the case (confirmed by listening on one side, then the other, then underneath, and then with the needle-stethoscope thingy). A couple of the aforementioned VW savants believe I might have too much crankshaft end play, which matches the ticking noise, the oil leakage, and the overall condition of the motor when I bought it from a Formula-Vee racer. Short of a rebuild, it is what it is; nothing I can do until it starts to bleed to death on some future grey day.

Second, I've got the engine to a daily driver condition where the leaks don't trouble me much. Stock air cleaner on top, slightly thicker oil (Royal Purple 15W-40 with zinc), keeping the level to between min-and-max markings, limiting my speed to 60 mph, and watching the throttle on hot days all adds up to a driveable bug. If I had it to do over again I would probably paint the engine black, rather than red, because all those little heat-shedding tricks add up. Red looks great, but for a daily driver I would have selected the plain-but-functional black paint job.

So, that's the cherry on top for this thread, based on all I've learned. Another hat tip to thesamba.com feedback providers, and I hope this helps you future readers.

[KTPhil]

If the endplay can be cured by re-shimming the flywheel, you don't need an engine rebuild.
If the bearing itself is loose in the case, then yes, case machining is needed.
_________________
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[wdfifteen]

[pdb27]