JS Motorsport
 
 
motorcycle
HIGH-PERFORMANCE
PARTS
FOR NORTON TWINS
JS Motorsport
4480 North Academy Avenue
Sanger, CA 93657
Phone/Fax: 559 875 0659
Email: jim@jsmotorsport.com
JS Motorsport Technical

WEIGHT/VIBRATION SAVINGS


JS Motorsports' forged pistons for 750cc Nortons each weigh approx 190 grams, compared to 250 grams for a stock Commando piston. 850 pistons weigh approx 210 grams compared to 317 for a stock piston. High strength .708" pins will save about 18 grams each compared to stock pins. Our Longer, lighter Carrillo rods will save about 30 grams each on the small end compared to standard Norton steel Carrillo rods because there is no need for a bushing when using the DLC coated pins (the small end is what shakes your bike), Our rod small ends are also approx 30 grams lighter than the aftermarket aluminum rods which have been known to fail. Big end weight is similar to the standard length bushed Carrillo rod and the stock Norton rod.

These important weight savings reduce vibration and stress within the motor, thus a reduction of the shaking forces by approx 1/3 with JS Motorsports' rods and pistons, and that means 1/3 LESS VIBRATION. Translation = Smoother ride. The reduction of shaking forces and related stresses help to save your cases, crank and everything else from failing, and that can save you lots of money

Piston weights etc & valve spring rate comparisons
>
JS lightweight bare pistons 750cc = 185 g 850cc = 210 g
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
Stock pin 750cc = 68 g 850cc = 72 g
JS Beehive valve spring 42.3 g TI retainer 4.7 g rate 324 lbs per inch Street seat pressure 90 lbs
Race seat pressure 130 lbs
RD racing spring 59.3 g TI retainer
10.8 g

rate 318 lbs per inch Race seat pressure 130 lbs
Stock spring 59.7 g steel retainer 16.1 g rate 280 lbs per inch

Street seat pressure 85 to 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