Topic: 1978 cb550 engine rattle under load. Any help?

[eigenvector]

eigenvector - Cam chain is probably original as far as I know.  It's taut and the movement is good, I checked by watching the movement of the valves while moving the engine via the big nut on the points mount.

I don't see how you can check the cam chain by turning the engine and watching the valves.  If the cam chain is original, it's pretty dang old - but more importantly than the age of the chain is the condition of the tensioner and guide, plus how far the tensioner has to move in order to bring the chain to proper tension.

All that aside, I do not wish to steer you in one particular direction, troubleshooting over the internet is dang near impossible.  I can think of 3 possibles, and if you're able to reproduce it at idle by reving the engine then it can't be the primary drive chain - although it may be the chain that goes from the crankshaft to the clutch.  The 3 possibles would be a valve, bearing (cam or crank), or cam chain vibrations.

Easiest way to tell is whether or not there is metal in the oil.  Another way - the old screwdriver tip to the engine handle to the ear.  When the tip is close to the source the noise will get very obvious.  There is a final option - that there's absolutely nothing wrong at all and you're chasing ghosts.  Don't ignore that as an option.

[Ceebeehead]

eigenvector - I was advised by another member that you can theoretically inspect cam chain slack by moving the crank and watching the delay, if any, of the valve movement up and/or down.  Maybe bogus, maybe it's a good way to check.
Instead of checking sprocket movement while moving the bike, I checked in the oil fill plug at the clutch pack while moving the crank in gear, no slack either way it seems.

Steer me in any way necessary.  Unable to reproduce this at idle as it only happens under load around 2500 rpm and whilst moving.

Redid the valve adjustment, still within specs.  Rode it with the timing 3-5 degrees retarded and advanced, no change either way.

I had an oil pressure gauge for the longest time and it always showed good readings.  About 40-50psi on cold start up and lowered to about 15psi at idle and proportionally went up with engine speed.  I took it off a few month ago.

In my desperation I started to look into pinging due to carbon causing hot spots or higher than usual compression ratio that even 95 octane couldn't overcome.  So I saw a good layer of the stuff in the cylinders.  Got some pics.

Is this too much carbon?

I poured some atf/seafoam/marvel  mystery oil cocktail into the cylinders and let it sit a few days, started her up and revved the piss out of her and rode around.  Still rattling.  Almost seems more evident now.  It might take a few sessions of this to clean it up enough to rule it out.  I thought about trying the water spray through the air box, and I've heard about the rice in the cylinders too.

Just an update I guess at my struggle.  I still have yet to bite the bullet and open up the oil pan and check it out.  My head gasket is seeping very little as are some of the lower covers.  If, and when, I fix this, I'm looking into a reseal and cleanup of the engine.  Thank you fellas for all the input.  I'll continue putting the advise into action and keep trying.