Motorcycle Repair: 85yamaha pw50 y-zinger, compression gauge, cause havoc

Question
just bought a 50 from neighbor. only $100. runs but doesn't have a lot of power. it seems like a carbeurator problem, wnats to bog down about half throttle. starts and idles fine.

Answer
Mark,
 Could be any host of problems.  First get a hold of a compression gauge and test compression.  You should be getting AT LEAST 80 PSI and at most 125 PSI.  If this is ok then your next order of business is to test the spark.  W/ plug firmly in the plug wire cap, hold the threads against any bare metal of the bike and kick over.  You should see a STRONG BLUE spark.  If so, you may be dealing w/ a improperly set and/or gummed up carb, both of which can cause problems.  Here is some info I've given others on cleaning and adjusting carbs.  You may want to buy a Haynes or Clymer aftermarket manual to consult with, especially dealing with the specs and tolorances:

Disassemble, clean all jets and orifaces with solvent and COMPRESSED AIR ONLY, use NO wire or picks to clean holes/airways. Rebuild carbs with new gaskets and make sure your floats are set correctly. . Do not overlook the float level, be very sure you are not starving for fuel. In relation make sure fuel flow is unobstructed and use a good in-line fuel filter from the tank to the carb. Even tiny particles in the fuel can get logged in critical areas and cause havoc.

Hope this helps,
Mike