A leak downstream of the carbs will make it run lean, ie the inlet manifold area. Have you disturbed the power bottle thingies when you were refitting the gearbox breather? Are all the solenoid pipes properly connected?
Is there loads of oil in the exhaust gasses? You can generally feel it if you rub your fingers together in the exhaust stream. There's likely to be loads of soot in the exhaust gasses if it's too rich aswell. Try holding a piece of white paper up behind each pipe and look for crappy deposits.
Laast thing of course is electrics. How strong are the sparks? A weak spark or knackered plugs will struggle to jump the gap under load. Are the plugs properly connected?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
