400EX engine Torque specifications
from the '99-'01 TRX400EX service manual

Maintenance
spark plug -- 13 lbf-ft
valve adjusting hole cap -- 11 lbf-ft
valve adjusting lock nut -- 17 lbf-ft
crankshaft hole cap -- 5.8 lbf-ft
timing hole cap -- 7 lbf-ft
engine oil drain bolt (crankcase) -- 18 lbf-ft
engine oil drain bolt (oil tank) -- 14 lbf-ft
engine oil strainer screen (at oil tank) -- 40 lbf-ft
oil pipe joint flare nut -- 14lbf-ft

Cylinder Head/Valve
cylinder head cover bolt -- 17 lbf-ft (NOTE; Chuz emailed me to let me know that this spec in the service manual is incorrect.... the correct spec is 8 lbf-ft, not 17... thanks Chuz!
rocker arm shaft -- 20 lbf-ft
intake sub-rocker arm shaft -- 20 lbf-ft
exhaust sub-rocker arm shaft -- 20 lbf-ft
cam sprocket bolt -- 14 lbf-ft
cam tensioner plug -- 2.9 lbf-ft
cylinder head nut -- 33 lbf-ft

Cylinder/Piston
cylinder bolt -- 33 lbf-ft
cylinder stud bolt -- 33 lbf-ft

Clutch/Gearshift Linkage
clutch center lock nut -- 80 lbf-ft
primary drive gear nut -- 65 lbf-ft
gearshift drum stopper arm pivot bolt -- 9 lbf-ft
gearshift spindle return spring -- 17 lbf-ft

Altenator/Starter Clutch
flywheel bolt -- 94 lbf-ft
starter clutch bolt -- 22 lbf-ft
left crankcase cover stud bolt -- 7 lbf-ft
gearshift pedal pinch bolt -- 14 lbf-ft

Crankcase/Transmission/Crankshaft
mainshaft bearing setting plate bolt -- 9 lbf-ft

Lights/Switches
neutral switch -- 9 lbf-ft