Motorcycle Repair: loss of power on honda CB450 K1 69, honda cb 450, honda cb450

Question
hi, i'm trying to fix my honda cb 450 k1 for over 6 months.
i've clean the carbs have them synchronized by a mechanic, change the air
filters
changed coils and plugs caps  and spark plugs, new petticoat adn fuel lines.
it was running ok like never over 7000 rpm never over 55 mph
yesterday i changed the head valve gasket and since then it doesn't run, no
more power even in full throttle no power no speed , just dead. it a oem new
gasket and i cant understand what happened.
thanks

Answer
Daniel, you'll have to go back through what you did to figure out what's not right.  The replacement of the gasket certainly doesn't explain the problem.  I assumed you had to take the fuel tank off to get to the cam covers.  The problem could be a bad coil ground, fuel delivery, reversed plug or point wires, or something like that.  Are the throttles opening and closing properly?  Is one of the chokes plates closes?  THere's a flat metal bracket that ties the two choke together.  If that came unhooked from one of the carbs it could allow one choke to close causing this lack of power.

Regards
Rich