CB550F Head damage - is this normal?

D

Dodge2000

New Member
Taken the head off my CB550F. Around where the valves seat, the brass ring is heavily pitted on cylinder 3&4. Cylinders 1&2 don't show anywhere near the same amount of damage.

It looks like there has been something metal banging around in there. The piston surface looks pretty clean, tiny amount of carbon deposit, but no damage at all, the piston bores are also really clean.

I hope the attached picture comes out on this. Is this normal? I can't see anything that might have caused it and there is no similar damage anywhere else around the engine.
 

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Normal? No.
But I don't have enough experience to tell you what did it. I'll let the experts chime in.
 
Ouch. Something went through there - either a rock or more likely a piston broke up. If the pistons look OK, they were probably replaced after that disaster. What numbers are on all 4 piston crowns (hint: they may not be the same)
 
Check your carburetor butterflies for missing screws....maybe you ingested one.
 
I would agree with teazer and mydlyfkryzis, except that you mentioned you're having the problem in more than one cylinder. I think what you may have is pitting due to detonation. Possible that those two cylinders were running lean?

Are those two cylinders the furthest away from the petcock? Also, as one cylinder begins to overheat, it may pass that additional heat into the cylinder next to it, and so it's not uncommon to see two bad ones next to one another.

I suspect #4 went bad and #3 then started overheating. Being an inside cylinder it would be more likely to be affected. It didn't carry over to #2 because the separation due to the cam chain pathway.

Either way, you'll want to clean that up. It can't stay that way. It'll probably be cheaper to buy a new head, though.
 
Matt, That doesn't look like detonation. It's mechanical damage. The copper coloration is a trip though.

The indentations do look like a broken piston ring and that raises all manner of questions as to where those parts came from and how they came to be together in one engine.
 
teazer said:
Matt, That doesn't look like detonation. It's mechanical damage. The copper coloration is a trip though.
Click to expand...

On two cylinders though? I suppose both could have broken rings, but usually that's a symptom of another problem and not the problem, itself, right?
 
What caused the conflagration is always the right question. The head damage was because something broke up. The questions are what, when and why.
 
The coloration is likely due to heat all those metal bits floating around in there probably caused some Pre-Ignition of the fuel charge.
 
I'd got to taking the head off as when I picked up the bike it stranded me after 50 miles. When the throttle was wide open it would lose all power and stall. My thoughts was that it was leaning itself out with wide open throttle. It was running standard airbox, but with the top off and some cheap 4-1 exhaust.

Don't think this caused the issues though, as no other damage anywhere else and think that the pistons have been sorted while the head was left.

answer to the petcock question. yes, these are the two cylinders furthest away. Head gasket looked in good shape as well
 
What size are the pistons? There should be a size marked on the crown somewhere
 
could be 374 instead of 574, no markings on the top of the piston. 12 on the rear of three of the pistons, 11 on one. They are Honda stamped pistons.
 
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