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Q In the February, 2007, Service column, you answered Jim Lang’s question about his 1984 Honda VT700 (“Me and my Shadow”), which didn’t have good top-end power. This same thing recently happened to my Honda ST1100. It performed normally, including its fuel economy, at throttle settings of one-half or less, but it could barely break 100 mph on the top end, had sluggish acceleration at highway speeds and had difficulty maintaining speeds up the mountain grades in Colorado. There was no apparent misfire, but the exhaust note didn’t seem normal, either. It turned out that three of the four carbs had holes in the diaphragms that lift the throttle slides, so those three carbs were incapable of reaching anywhere near full throttle. Maybe Mr. Lang’s bike has the same kind of problem. Michael Martin

Louisville, Kentucky

A Excellent observation, Michael.

When responding to Lang’s inquiry,

I considered the carb diaphragms but foolishly assumed that when he stated,

"I’ve had it to the dealer for service and everything checks out fine,” that meant the carbs had been inspected and deemed fully functional. That was a poor decision on my part. I don’t know for certain if Lang’s Shadow was suffering from damaged diaphragms, but that certainly is a strong possibility. Thank you very much for the useful input.