Oil pools in the air box

[Barry]

Could a bad air filter cause this?

Not very likely.  The air filter lasts a long time before it causes problems.

Did you find the oil drain hole ?  I wasn't 100% certain before and perhaps still not but having done some research and looking at your pictures again I'm thinking that type 248 engines (that's both early and later R45/65's)  don't have the same drain hole that other post 78 type 247 airheads have.   There is almost no information anywhere to confirm this even on Snowbums site but it can be deduced from the style of the breather cover and that fact that it exits vertically and turns down before being teed off to each carb intake.

Why they didn't apply this drain hole mod to the type 248 block I don't know. Perhaps they thought crankcase breathing was less of a problem on the smaller capacity engines and also thought the vertical rise would help compared to the early breather covers which had a horizontal outlet.  Anyway don't be concerned if you don't find the drain hole.

[Einar]

Thank you for the response Barry. Great input!

I did not find the oil drain hole when I took the engine cover off. I will repeat the exercise this weekend and have another look according to the uploaded cross-cut photo.

I'm unfamiliar with the differences 247 vs. 248 but from your comment I assume mine is a 248? Model year 1981.
It does appear the cross-cut is slightly different than the on my bike. Ref. your 247 vs 248 comment.

What puzzles me with this drain hole is:
Does it make sense to put a 'return-to-sump'-drain outside the breather valve. Wouldn't that be designing with a leak in mind?

Will check again this weekend once I'm back home from travels and update the post when I have some new information.

[Barry]

I'm unfamiliar with the differences 247 vs. 248 but from your comment I assume mine is a 248? Model year 1981.
It does appear the cross-cut is slightly different than the on my bike. Ref. your 247 vs 248 comment.

What puzzles me with this drain hole is:
Does it make sense to put a 'return-to-sump'-drain outside the breather valve. Wouldn't that be designing with a leak in mind?

 

Yes yours is a type 248.  That's just shorthand for the short stroke R45/R65 engines.  Although there are many common features, the longer stroke type 247 engines in R80's R100's etc use a different block.  Type 247's have for example different angled pushrod tubes and in the case of post 78 engines the said oil drain hole which I'm suggesting the type 248 blocks don't in fact have.

On the engines that do have the drain hole, Although I see what you mean about a designed in leak bypassing the breather, I think it still makes sense to put it outside of the breather valve to give any condensed oil vapour a chance to return to the sump rather than pass through to the carbs. Providing it's able to cope with any piston blowby the breather is designed to keep the crankcase at a slight vacuum so the condensed oil would be pulled in through the drain hole.

[Einar]

Thank you for the clear explanation, Barry.

Once I can verify the presence/absence of the drain hole I will update the thread. If it's there, I assume it must be located directly in front of the air box or in the sump in front of the breather valve.

Will keep you posted.
Cheers.

[Einar]

Hi all,

Just to close out this topic with my final findings.

The problem was two-fold and rather simple:

1. The hose that goes from the oil-breather valve and into the airbox was poorly attached and leaked oil vapour.
2. The gasket on the breather valve had never been changed and was practically melted into the steel.

3. In addition, I maintain, as advised, an oil level slightly on the lower side of the dipstick interval.

After having addressed these two things, the oil leaks have now stopped completely so the airbox and top of engine block are now oil free.

Thank you all for your help on this. I learned a lot.
E/