VF1000R Carb sync question

Hello everyone, I just scheduled my third carb sync appointment with a different shop than the first two. Hoping to smooth out lower engine knock when RPMs reach @ 4000. I read a post ealier that this may be one of the causes. From riding recently I'm noticing a heavy smell of fuel from exhaust. Carbs were rebuilt by two brothers Honda two years ago. Bike runs very smooth until reaching 50-55 MPH at 4000RPMs in 5th gear. Any ideas or suggestions to make for the mechanic when dopping the bike off?........Thanks

 

I'd say 99.9% sure it's not the carb sync that causing your problems. Only a really badly out of sync set will cause any noise, and you'd be more worried about how rough the engine was running to care about any noises. Carb sync helps with overall engine smoothness but will not cure an RPM-specific problem.

That said, I can't really say what would cause a noise right at 4000rpm and nowhere else. Care to elaborate?