Overhead cam motorcycle engines generally have a chain that connects the camshaft to the crank. Over time and miles a rattle in the chain may develop. Some chains have an automatic tensioner, while others need manual setting of the chain tensioner. This adjustment should always be done after the engine has been properly tuned.
If after setting the cam chain tensioner a rattle persists, one might assume that cam chain or tensioner replacement is required. This can often be an expensive repair job. Before you resort to that option, on multi-cylinder engines you should check that your carbs are in good condition and properly synchronized.
Carbs that have been badly gummed up at any time in their life may not be operating efficiently, and are often impossible to synchronize perfectly. Or possibly the carbs are in good condition but have not been balanced (synchronized) in a long time. This can result in erratic firing of one or more cylinders, and the uneven operation of the engine causes any slack in the cam chain to be amplified into a rattle.
One quick test that will indicate a possible carb (or other tuning) problem is to feel the temperature of each exhaust pipe shortly after you start the bike, before the pipes get too hot to touch. They should all feel about the same temperature at a point close to the engine.
So, if your cam chain is noisy and all attempts to quiet it down have failed, have a closer look at the condition of your carbs!
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