Motorcycle Repair: 1991 Honda Shadow 600 - Fuel issue?, honda shadow 600, intake tubes

Question
Wayne.  I have a 91 Honda Shadow 600 (with a duel carb this model year).  I recently taken it to the authorized local Honda Repair facility here in Marin (Cote Madera) Ca. They replaced the carborator.fuel filter and adjusted the carb total tune-up, etc, etc...  The problem is when I have her on the highway she begins to buck at the top and easing off on 3 rd gear.  It feels like its looking for fuel. The mechanic says he can't figure it out without me putting ALOT more $ into it...I have already put about $900 into it.  Thought maybe you have had edxperiance with this issue on this model that might give me and him some insight.  I'm not a mechanic..but it feels like timing or valve adjustment when it gets to the speed it begins to "hunt for fuel"..bucking...unsmooth operation... Got any thoughts?  This bile only has 7K on it...I'm torn weather to sell it or fix it. When I go to sell it..the buyer is not gonna like the way it bucks eitrher.  I don't want to loose my ass on it. Thanks...R Decker San Rafael, California 415-710-2791

Answer
Reid,

it may be looking for fuel for various reasons.

-does it do it any more frequently when hot/cold?

-When fuel gets really hot it boils before it
gets to the motor causing the bike to cut out and
come back. You might want to insulate the fuel
line from the heat with heat wrap or similar.

-Condensation can form in the tank and cause fuel
problems. Try some additive to displace moisture.

-Take a plug reading to see if the engine is running
lean (whitish) or rich (black) at the bucking speed. Stop the
engine quickly after letting it buck a bit.

-Possibly a bad plug wire or cap or pulser coil
failing when hot.

-The intake tubes and exhaust system should be
checked for any leaks also. This can cause a
lean condition as well.

-Gas tank vents can plug up and cause a vacuum
in the tank that holds the fuel back.
-Plugs and air filter were done, right?