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I've got my bike in the shop with exhaust repairs but before it went I noticed a noise from the left side of the engine.

Honda cbx 550 dohc straight four.

Sort of a shuh shuh shuh or shih shih shih sound at idle but seemed to disappear (or speed up?)when I revved the engine though I can't be sure because of the overly loud exhaust. It might even be characterized as a gasping sound

I'm wondering if it is a vacumn leak at the intake maybe but am fearing something alot worse like worn out cam chain, valve, camshaft bearing...

head gasket???exhaust leak??

It doesn't appear to be losing oil. Wouldn't there be a loss if there was an headgasket leak? I'm thinking of when I get it back tomorrow I'll spray some carbcleaner around the intake manifolds to see if that is the prob. I want to eliminate the simplest first. May be a cracked plastic intake.

It manifested when the patches I'd put on the rotted mufflers blew off on a highway ride and probably ran leaner than usual on two of the cylinders. It has a 4-2 exhaust. I put it in the shop to replace mufflers cause I'd rather not damage the engine and I don't like the noise of loud exhaust. Maybe an imbalance of some sort caused the noise?

Concerning looking for an exhaust leak at the head. Would I spray anything or just hold the hand to feel for gas escaping?

a head gasket will blow without any oil loss--sounds more like exhaust leak.you can take a propane torch and hold it close to the header pipe and rev the engine up and let off the throttle.if it is leaking it will pull the flame to the header.