Motorcycle Repair: Honda 1980 CM 400 Rmps, air fuel mixture, stock muffler

Question
Bought this bike with 4400 miles on it. It has a 2/1 pipe and aftermarket muffler. After 3 complete Carb cleaning(s)and soak. The bike starts easy. Idle jumps by 1-300 every few secs followed by a click in the carb as it adjusts back. Big problem is under load Between 3000-4800ish RPM it hesitates for a few secs to get past.(in every gear) Before and after that range the bike Screams perfect. I do know the carbs need sync because I did a full breakdown. But the Problem was there before dissasembly. Didnt replace any gaskets as they all seemed to be reusable. Could this be caused by a bad gasket between head and carbs? I am clueless at this point PLEASE Help!


Answer
Dan, it sounds like the engine is running lean. With a 2/1 pipe it's probably less restriction than the stock muffler so you will need to richen up the air fuel mixture a little.  You can do this in a couple of ways. If it a mid range only problem, you can install a couple of small washers under the needle valves in the throttle slides. If you pop out the slides you will find a screw in the middle of the slides holding the needle valves in.  Go to the hardware store and buy some small washer about .020 inch thick and put one or two under the needle.  Another way to go if you need to richen up the whole range is to raise the float level 1.5 mm.   

I can't explain the clicking in the carbs unless the throttle are sticking open and you are hearing the click as the throttle hits the idle screw stop.