Topic: Question for the Pros. Weird hole in valve cover?

[CaptFatCat]

CB750 K7,
Sat for 15 years in a garage, removed the valve cover and found 2 weird holes in the cover between the cam sprocket housing and the breather tube area. It almost looks like a bad mold because of the thickness of the metal and the wrinkles in the mold. I dont see any place where the cam chain may have rubbed but thats kinda what it looks like. If oil gets slung into it from the cam chain it will seep into the drain in the breather chamber or seep back thru the lower hole.
From the looks of every case screw on this engine I would say its never been opened up. The bike came in a basket and the speedo says 20k miles.
Has anybody ever seen this before? Do you think its a factory defect?

[Bodi]

I don't believe that would go unnoticed for 20k miles. Is there a lot of staininb on the outside, blowby leaking out would leave a lot of goo.
Possibly in its basket, rain filled the cavity and broke it on freezing? Have you looked for the missing bits?

[CaptFatCat]

No Missing bits. No freezing rain (Florida). the area of the blow by a looks clean. the material is very thin in that area like it didnt get enough pour from the factory mold. Motor turns nice with the kick start. Cam chain and sprocket looks good all the way around.

[pjlogue]

One of the holes os supposed to be there.  It is the crank case vent.  If the shoulders that support the 2 screws are intact and can take to torqued down screws that go into the head you should be OK to use it. 

-P.

[jamracing]

May have thrown a cam chain at some point?


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[robvangulik]

Imagine for a moment those holes aren't there.
How would any air get to the crankcase breather chamber?

[CaptFatCat]

Through the weep hole at the front #3 corner of the breather is the only other passage, its about 4mm round.

[disco]

Possibly your cam cover hasn’t been cleaned real well after the casting process.

[CaptFatCat]

Thanks Disco,
I think that is it exactly.
Your pics shows where my holes would be if they were cleaned up after casting.

[disco]

Time to get the Dremel out!