Oringinal piston specs.

Piston specs for Bros J and K.

Piston specs for Bros L.

English piston specs for Bros NT400 J/K, accuracy not guarunteed.

Item.	Standard NT400 J/K.	Service limit NT400 J/K.
Cylinder bore	64.000 mm - 64.015 mm	64.1 mm
Cylinder warpage across top	-	0.1 mm
Cylinder taper	-	0.05 mm
Cylinder out-of-round	-	0.05 mm
Piston Diameter	63.96 mm - 63.99 mm	63.9 mm
Cylinder to piston clearance.	0.01 mm - 0.55 mm	0.1 mm
Piston H (look at picture)	10 mm	-
Clearance between piston and piston pin	0.002 mm - 0.014 mm	0.04 mm
Clearance between piston pin and connecting rod small end	0.016 mm - 0.040 mm	0.06 mm
Piston pin OD	14.994 mm - 15.000	14.98 mm
Piston pin bore in piston	15.002 mm - 15.008 mm	15.05 mm
Connecting rod small end bore	15.016 mm - 15.034 mm	15.07 mm
Piston ring to ring grove clearance, top.	0.025 mm - 0.060 mm	0.08 mm
Piston ring to ring grove clearance, second.	0.015 mm - 0.045 mm	0.06 mm
Ring end gap, top.	0.20 mm - 0.35 mm	0.5 mm
Ring end gap, second.	0.35 mm - 0.5 mm	0.7 mm
Ring end gap, oil.	0.2 mm - 0.7 mm	0.9 mm