Motorcycle Repair: Yamaha Maxim 400 problems, motorcycle shop, valve adjustment

Question
Falcon, First off thanks for your time and expertise. I have a 1982 Yamaha maxim 400. I got the bike for nothing but am having some trouble with it. Expected this being it was free.when i get her started she idles up and down...im already figuring it needs a good carb clean being it was sitting for 2 years.The big problem i noticed this morning is i changed the oil  a week ago and all was fine. when i looked this morning the oil was overfilled. when i drained some out there was actually gas mixing in with the oil. i could smell it as i drained it and you can see what oil came out was thin due to the gas getting into the engine.Also before i realized this i had it running but it was working hard to get over 45-50 mph. she still starts up but with the oil thinning out i dont want to ride it and cause severe engine damage.Any advice or tips you have would be a great help...thanks again
                              George Smith
                              Duanseburg,NY

Answer
Hi George.

Start by doing an oil change. Then replace the air filter, if you already haven't, and clean the ENTIRE fuel system; clean the carbs, replace the fuel line, disassemble and clean the fuel valve (or replace the valve altogether) and reseal the tank.  Tank sealing kits can be had at any decent motorcycle shop.

Synchronize the carbs and do a proper valve adjustment.  The specs and proceedures are in the repair manual.  If you do not have one, then get one.  It is worth it's weight in gold.

 Next, check compression.  Make sure that the compression is within specs as well.

Start with those and let me know what you find.

Good luck and ride safe.
FALCON