Motorcycle Repair: carbs, kawasaki 750, jet size

Question
i recently had my carbs works on by a local mechanic. my uncle and i built them from two used sets of carbs, this is on a 1981 kawasaki 750 four-cylinder. the mechanic upped my jet size to compensate for my high flow k&n airfilters i just installed. the bike when i took it out was hesitant and doggish with bursts of power and then loss of power. (this bike maybe has not been significantly ridden for 10 or more years) i ran it at high rpms in first gear to keep the thing moving and after less than a minute the bike seemed to clear its throat and took off. ran smoothly and fast. now i cant get it to start at all. i suspect it is running too rich. this is a long story, sorry about that. if it makes any sense i'd love to hear about it. take care.

Answer
From the sound of it you may need to have the cylinders honed, re ring the pistons and possibly need new pistons. After sitting so long there may have been moisture in the cylinders causing corrosion, this could have sealed up the cylinders enabling you to start it... heat causing the pistons and rings to swell keeping compression. Once it cooled down you lost the seat and now... no compression.