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CB750/4 water damage to pistons

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Rob62:
A lot of damage on that piston crown.... probably why it was separated from the frame in the first place.

matthewmosse:
Wow, that is some severe damage. I think endoscope inspection before any startup attempts on unknown motors from now on in my shed. Admittedly it won't show the rings but piston crown and bore inspection will give a good insight as to if sutch horrors lurk beneath the crown. My own far more limited experience is that once engines contain that much damage and corrosion they often won't turn over well enough to run, still it's a worthy warning of what can be amiss in an engine that seems reasonable. I had a cb500 engine that kept eating tensioners but otherwise seemed extremely clean and low mileage. One day I'll tear that down and see what similar horror lives down in the crank end. Top end was mint, hardly even carbon on the head. The flip side of the coin is that for us less experienced engine dabbles can do more damage looking inside a motor that was fine before we set to with spanners.

Bryanj:
Matt most common reason for 500 damaging tensioners is if the holder gets a bit bent and does not locate in the correct place in crankcase.

Nurse Julie:

--- Quote from: Rob62 on December 17, 2018, 09:16:54 PM ---A lot of damage on that piston crown.... probably why it was separated from the frame in the first place.

--- End quote ---
If you are talking about the piston pics i put on, nope. The drive chain made a hole in the crank cases the size of a football which is very common on these early engines. The engine was removed from the bike having covered less than 1000 miles (approx).
If you are referring to the ones Trig put on, i have no idea.

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