JS Motorsport Technical Piston weights, lifters & valve spring comparisons and pressures

JS lightweight bare pistons med C.R. 750cc = 183 g forged or 175 g billet 850cc = 200 g forged or 185g billet 920cc = 210 g forged
Stock Hepolite bare pistons 750cc = 250 g 850cc = 317 g
JS bushless Carrillo rods small end 105 g big end 326 g
JS bushless Ultralight Carrillo rods small end 95 g big end 307 g
JS DLC pin 750cc = 51 g 850cc = 58 g 920cc = 58 g
Stock pin 750cc = 68 g 850cc = 72 g
JS Beehive valve spring 42.3 g TI retainer 4.7 g Beehive street seat pressure 90 lbs
Beehive race seat pressure 130 lbs
RD racing spring 59.3 g TI retainer 10.8 g RD race seat pressure 130 lbs
Stock spring 59.7 g steel retainer 16.1 g Stock street seat pressure 90 lbs balanced with shims.
100+ lbs shimmed for racing
JS (BSA) radiused lifter 38 g
Stock flat lifter 74.6 g
JS pushrod 31 g
Stock pushrod 32 g
JSM beehive springs, Free Length 1.845" Installed height pressure
1.700 35
1.650 46
1.600 58
1.550 70
1.500 81
1.450 93
1.400 106
1.350 121
1.300 133
1.250 147
1.200 165
1.150 185
1.100 205
1.050 225
1.000 240
0.950 256
coil bind .9 (.880 actual) 0.900 272