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Worst case scenario, its a cracked head.

Ken90

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to make a long story short, got this awesome nighthawk for a grand. I knew that I would have to do work, it was running when I got it and it ran all summer! then the timing chain snapped... literally snapped, good part was I was in my driveway. I took that bike down to the frame, and completely rebuilt it, I am mechanically inclined (I know the difference between inch pound and foot pound) and I like to do things the right way. if it needed to be replaced I replaced it. I put it all back together and it ran like a brand new bike (looks damn good in green too btw). towards the end of last summer I was going down the road when all of a sudden my exhaust just started to get louder and louder, I had no back pressure had a hell of a time getting up a steep hill. I drove it home and got to work.

What I know:
what ever it is its coming from #3 cylinder, extremely loud like their is no exhaust to speak of. lots of air shooting from the head, I have yet to pin that down yet (I'm about to tomorrow).

What I think I should
do: my hope its a plugged exhaust, at this point of head scratching I don't think it is. stuck valve (not bad), cracked valve spring, and worst case scenario, its a cracked head.

what do you guys think? any other ideas of whats going on? any input is incredibly helpful. thanks! Kenny
 
Year model and make would be a start, there's like 10 different Nighthawks.

Could have simply blown a head gasket. ALL engines pretty much get louder when a big chunk of power goes away, you automatically adding more throttle ('steep hill') to compensate does it.

Slow down and think. How can you have 'no back pressure' yet a 'plugged exhaust'??? A plugged exhaust would be ULTIMATE back pressure, which is pretty much a myth in correctly running engines any way.

Rather odd to crack a bike head, it usually requires physical interference with other parts to do it. Not that it hasn't happened.
 
so its an 1982 cb750sc, I pulled the engine yesterday and yep! I was over thinking everything. you where right, blown head gasket. gotta a new one on the way and should be riding next weekend.
 
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