Quote:
Originally Posted by rdruss
Started after cylinder head replacement for unknown reason. Maybe it dropped a valve on #2 and did some piston crown damage but not enough that they wanted to replace it. Some deep gouges in top of piston might affect compression ratio. Can you get a bore-o-scope into cylinder #2 and have a look?
I dropped a valve twice in a Yamaha TT500 and piston was ok, but on a single cylinder drop a valve and instant shut off, thus piston doesn't take a beating like on a multi-cylinder engine that keeps running.
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Probably damaged piston or mishapen cylinder wall due to overheating... The previous cylinder head was probably cracked at some point, causing loss of coolant and severe overheating. This may have affected the shape of cylinder?
Since cylinderleakdown is tested when piston is at top dead center, the air wouldnt go past the rings if the mishaping is further down the cylinder wall. Does this make sense?