Motorcycle Repair: my bike boggs, vacuum leaks, muffler systems

Question
ok, this is not a honda but what the hell. i have a yamaha, 4
strock fz 700 (1987). it sat for about 5 mouths now i started
ridding it again and it bogs down at about 7000 rpms. i didint
do it before it sat and dont know what it could be.  ive changed
the air, fuel, and oil filter. ive changed my spark plugs. i've
changed all my fluids (although i dont dought its that), and i just
got done rebuilding my carbs. what do u think it could be? my
carbs looked fine when i rebuilt them so i dont think its that.  
any other suggesting why it boggs down.

ps when i say it boggs down i mean that it wont go any faster
then 65 mph, if i try to open it up it just maintains its speed.  
even on neutral it wont go past 6000-7000 rpms.  

Answer
Well, MrHonda will offer a few suggestions, but I am not all that familiar with the intricacies of your model.

Yamaha, in the past had had variable intake manifold runner/butterfly systems that kicked in at higher revs, as well as variable exhaust valves in the muffler systems. If either one, assuming that your bike has one or both systems is jammed up, that could be a factor.

When bikes won't rev over a certain rpm, even in neutral, then I would look at some kind of air flow issue, either intake (air filter) or exhaust blockages.

Other factors could be:
Low battery voltage, which is affecting the ignition module and spark advancer curve.

Plugged vent system for the fuel tank.

Plugged/restricted petcock passages.

Failure of the spark advancer system, either mechanical or electronic

RPM rev limiter malfunction.

Carburetor fuel enrichment system not shutting down, adding extra fuel all the time.

Manifold vacuum leaks at manifolds or any vacuum lines coming from the carburetors.

Spark plug cap resistance too high or plug caps loose on the wires.

Ignition coil problems or wiring issues.

Check the web for any FZ related groups or websites that specialize in this model.

Bill Silver