What's this hole for?

[steve_wicks]

I rode my bike the yesterday after it had been left uncovered in the rain for a few days while I was away and was horrified to see water bubbling out of a hole in the tappet cover tight near the spark plug.

The holes are on both tappet covers which are fitted upside down or left instead of right by previous owner.

What is it for, what's behind it etc? :-?

[Justin B.]

Well, none of mine have a hole there but what is behind there is just an empty/open area that is/should be sealed off from the "important" parts.  Maybe somebody that didn't know better tried to pry them off at that point before they realized there were a couple other retaining nuts they forgot.  

Put the covers back on the correct side and maybe the oles will be on the bottom - plus they look better!

[montmil]

...What is it for, what's behind it etc? :-?

What's it for? One of two things: 1) To cause you a bit of grief; and, 2) A place to hold your flat-blade screwdrivers.

I'm with Justin on a ham-fisted PO trying to pop off the covers after removing only the center stud nut.

The entire rocker arm/valve actuating systems is behind that hole and doesn't need a water rinse every time it rains. The lubricating oil to the valves then drains back into the crankcase... perhaps along with any water that doesn't boil off during engine ops. Hopefully, the cover gasket is doing its job but you did mention water bubbling out.

A decent machine shop could likely fill the gap with an aluminum weld puddle then dress it down flat. The valve cover gasket is plenty thick so any small inequities remaining would be sealed up proper.

Monte [smiley=2cents.gif]

[Justin B.]

Monte, if you look at a valve cover closely the middle part is not connected to the portions where the valve-gear is located - but it does need to be addressed...  At least that's the way I remember it, but I could be wrong.

[montmil]

Monte, if you look at a valve cover closely the middle part is not connected to the portions where the valve-gear is located - but it does need to be addressed...  At least that's the way I remember it, but I could be wrong.

That's right! I recall now after reminding myself what a gasket looks like, plus my not too recent helicoil install. Oops. Must be the drugs still hanging on...

So how did the agua get in there? or did it? Maybe just residual moisture cooking off from the screwdriver pounding.

Time to R&R the covers for a visual.

[Justin B.]

Mmmm, drugs!!!    Probably anytime you get caught in the rain, or wash the bike, will get water in that area.  Me thinks if he puts them back on the correct sides then the holes would be on the bottom.  He could then possibly use JB-Weld (or similar) as a filler and it would be out of sight.  I've used JB-Weld like "Bondo" on small dings on vintage Chevy valve covers with excellent results.

[chopper_harris]

I rode my bike the yesterday after it had been left uncovered in the rain for a few days while I was away and was horrified to see water bubbling out of a hole in the tappet cover tight near the spark plug.

The holes are on both tappet covers which are fitted upside down or left instead of right by previous owner.

What is it for, what's behind it etc? :-?

The cambox covers are handed - 761 is LHS, 762 is RHS.
(fyi, when BMW produce a 'handed' component pair, the LHS is always the lower number)

The barrels are not cast parallel to the ground, but slope slightly down front to rear.

If you get the cover aligned correctly, the fins WILL be // to the ground.
If you are 180' off, they will clearly out by eye when standing to the side of the bike.

The bubbles are due to water 'cupping' in the gouge.
The cambox is slightly pressurised due to blow-by along the valve stems.
This is finding it's way to atmosphere via the gouge.

No reason to worry, but a good excuse to treat yourself to a pair of the splendid kidney shaped pre-78 covers  

[steve_wicks]

Yup, Thanks.

Just got to get gaskets, at the moment it seems covers have been fitted with silicone.

I have also got a bit of an oil leak at the base of the r/hand cylinder and there are signs of silicone around there as well - so torqueing the heads and re-setting tappets will also be done at the same time.

[Darwin_R65]

My bike looks identical, and after rain, I get the boiling water from the hole display as well. Only noticeable when I've stopped and i lean the bike slightly one side or the other.

John

p.s my left cover is marked left and right cover is marked right, so they're on the right sides.

[Semper Gumby]

I am now quite used to the sound of boiling water after riding my bike home after it has sat out in the rain.   8-)

[Rob Valdez 79 R65]

I am now quite used to the sound of boiling water after riding my bike home after it has sat out in the rain.   8-)

+1

For 29 years, now.

[steve_wicks]

Okay ...... I had visions of rusted rockers and all sorts of other horrible things