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New (to me!) '77 CB400F - US model
mattsz:
While the old oil that I could see (lifted on the dipstick, pumped up to the cam shaft when cranking the engine over) looked clean, I found it wasn’t really so. The drained oil was pretty black, as was the filter. The filter cover had some dark residue settled in it - bearing material? combustion products? both?
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The oil pan itself came off easily, no overtightened bolts. Of course, I couldn’t access them all with the exhaust in place, so the headers had to come off (except for the common surface rust around the tops, the rest looks good, including the collector). There was a fair amount of the dark residue in the pan as well; not sure how it compares to some others I’ve seen… recall the bike shows 26k miles, and the cam shaft bearing surfaces look pretty good - haven’t laid eyes on the crank bearings though…
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mattsz:
I dredged the oil pan muck for debris - here’s what I found. The flecks on the rag remained after the black oily residue soaked in - metallic looking, but seemingly more like paint flecks:
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The pieces above the rag are proper metal shards:
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There isn’t any obvious evidence that the pan has been off before - except for one strange thing: near one of the mounting holes for the “oil separator plate,†there’s some spiral skip marks which look like someone was trying to drill the hole and allowed the bit to wander off… twice! I can’t imagine that would have happened at the factory… but why would anyone be waving a loaded drill bit in that direction?
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mattsz:
Finally, the oil pan appears to be cracked (hmm... thumbnail upside down again?):
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It’s not, however, in the “usual†spot, around the drain hole. Plus, no matter how carefully I look, I can’t see any evidence of it on the inside:
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Is it possible that there’s some sort of fracture that doesn’t go clear through?
K2-K6:
The shrapnel looks slightly concerning, that piece of an arc appears to be heading toward 20/25mm diameter and at a preliminary guess could be something from the gearbox. Are you continuing to strip motor?
The sump "crack" you could tip it at a slight angle and put petrol into it to above the crack line to see if there's any pathway through it. Generally a crack in casting will pass all the way through it even if pinched tight on opposite face, I'd suspect it would need attention all things being equal. Cleaning with a solvent prior to getting it Tig welded would probably be a decent solution, and leave the weld seam in place, not ground off.
The sump looks almost as if the bike has been lifted by jack on the sump plug at some point, not the usual clobbered on the ground that's often seen.
mattsz:
Thanks K2-K6!
If it matters, the curved piece appears to be more like a 12mm diameter rather than 20-25mm...
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... but to be honest, when examining it closely from all angles, it looks more like a curved shaving rather than a broken piece pre-formed at that arc. I was not planning to strip the motor at this point, I intended to see how it runs first!
(FWIW, that pile of rubbish looks very much like what came off the oil strainer during my 2011 Royal Enfield's first oil change! ::) ;D )
I'll leak-test the sump once I get a new plug washer...
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