Motorcycle Repair: Noise in Engine, blown head gasket, worn clutch

Question
Hi Bill
Hope you can help.I have a 1977 Honda cb550f motorcycle,with 36000 miles.The bike has lots of power when accelerating going through the gears no odd noises until I pull the clutch in, before I change gears I can hear a ting,ting, sound or something loose in one of my left, two cylinders as if its bouncing off something, not a knocking sound.It also does it if I'm down shifting.I have tried to listen for this sound when the bike is idleing,turning throttle raiseing rpm's no sound the bike sounds great,annoying.I had the top end gaskets replaced in spring mechanic said the top end looked good.Except it started to leak again,a few weeks ago.As for me,I like to tinker with bikes but do not have experience with engines.I've heard the term piston slap before, but do not know exactly what it is.The bike overall is in above average condition and is worth repairing.I hope this gives you enough information.Is there a way to pinpoint where the sound is exactly coming from?
...Thank you Mike  

Answer
Mike, noises can generate from purely mechanical sources, like rocker arms, rocker shafts, wrist pins, connecting rods bearings, camchain tensioners, loose camchains (they need adjusting every so often), exhaust leaks at the flanges or blown head gasket between cylinders.

Non-mechanical sources could be that the engine is pinging or detonating due to carburetor metering problems, carbon buildup on the valves, worn valve stems/seals, air leaks at the manifold, incorrect spark plug heat ranges and inaccurately set ignition timing.

Noises further down, could be the primary chain being stretched out, failed/worn primary chain tensioner, worn clutch hub or release parts.

Piston slap is a term that denotes a piston that is worn or loosely fitted in the bore which is beyond manufacturers specifications and is rattling back and forth in the cylinder bore as it travels up and down.

Sometimes, you have a harmonic vibration in a component that will rattle only at certain rpms. If you have any accessory items like crashbars and forward footpegs, you can often find them as a source of noises.

From what I can gather in your description, it sounds like it is more engine load-related, which could be pinging or or clutch/primary chain sourced.

I would certainly have the compression checked, read the plugs when you have them out for the compression check to look for signs of detonation/overheating of the plugs. Recheck the valve clearances and especially the ignition timing with a dynamic timing light (engine running). Once that is all clear, then check carb synchronization, idle mixture settings and intake manifold integrity. If you have changed the intake (air filter system) or exhaust pipes from stock, then there is a possibility that the carbs need to be rejetted to compensate for the modifications.

I would drain the float bowls a bit to see if there is any water, dirt or debris floating around in the bottoms of the bowls. If the carbs start to overflow afterwards, when you turn the petcock back on, just turn it off again, keep it running and then tap on the carb body assy a few times with a plastic screwdriver handle to jar the float valves back up into place.

Kind of hard to say much more about it w/o hearing it personally, so fly it over to Hawaii and we'll see what we can figure out! :>)
Bill Silver