Standard engine

Well I had a standard engine in my pulsar, one day went out in it all fine then started to pop and bang and started misfiring. got it back to garage compression test showed low on compression cylinder 4 havnt stripped it down didn't make any unusual noises no knocking no tapping engine sounded really good but still was misfiring I personally think piston rings have gone on cylinder 4 didn't know Wat the engine is worth as it is!?? Anybody interested in this perfect for forge build!! OFFERS!!
 
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