Topic: Just bought a used '72 cb750 engine. Opened the oil pan and found some gunk.

[specialone70]

Looks like some silicone and metal (some was magnetic, some was not). The engine supposedly ran and has 20,000 miles (according to the guy I bought it from) and I paid $150. How'd I do?  Do you fellas think it's serious?

[seanbarney41]

looks fairly typical with these.  As long as the cam gets oil, it will keep running.  I would just run it until it breaks, then buy another for $150.

[specialone70]

I checked in the valve access ports and didn't see any soot (like I found in the engine it's replacing, which wasn't getting oil to one of the plain bearings) so I think we're good there. Thanks for the reassurance!

[seanbarney41]

Peek in the exhaust side tappet covers while it's running, if oil splashes out, your good to go for a while...basic tune up #$%* will totally help too

[PeWe]

Rubber from chain tensioners. I think these engines must be opened completely and replace chains and tensioners, the rubber wheels become hard and grinds into small pieces. Primary chains and cam chain.
Check if all clutch plates are intact. The alu like flakes can be clutch fiber plates. I have seen that in my engine.
Edit: Cam sprocket bolts can touch head if too long causing alu flakes. Mine were very close so I filed them shorter

[chewbacca5000]

Get a magnet and see if anything is attracted to it.  Does not look too bad to me.  Clean screen and pan well.