Motorcycle Repair: yamaha 400 reving, land speed record, lean mixture

Question
Hi Mike,
    I have a 1981 Yamaha 400, runs well etc.  15,000 miles on it.  Problem is, it revs to higher rpms between shifts.  I have to let  a few seconds go by before I can hit the clutch and shift. Otherwise it sounds like I'm trying to set a land-speed record. Throttle cable is free and not sticking open.  Someone told me that it might be a matter of correct timing.

    Twin carbs, carb problem maybe?

Answer
Greg,
 It's possible an overly advanced timing can increase RPMs but not to the level you are describing, not alone anyway.  Inspect the points for wear, charring and excessive sparking.  If you need to replace them do so along w/ a new condensor, very important.  Set the point gap AND position in accordance with a good manual.  What may be also happening here is an overly lean mixture caused by a leaky intake boot or gasket.  This will cause the lean mixture to run the engine hotter and cause premature ignition.  (the mixture can actually ignight from a glowing carbon ember in the combustion chamber or the combustion chamber is hot enough to light it itself).  
 2- strokes are my thing, the only thing that clued me in to your model was a 4-stroke was the 2 carbs. XS?  A bit confusing because there is an 81' YZ 400 2-stroke.  In two's this is mostlikely caused from a leaky crankseal, not the case on yours.

Good luck, hope this helps,
Mike