Lightweight Pistons & Long Rods

Lower vibration = increased reliability

The best piston/rod combination on the market. Our lightweight pistons (1/3 lighter than stock) are forged aluminum, making them stronger than original cast aluminum pistons. The combination of lighter pistons with our longer lightweight rods makes for a much smoother and reliable ride whether you are cruising down the highway or pushing it to redline on the racetrack. DYNO TESTS SHOW APPROX 7 MORE HP just by switching to the lightweight pistons and longer rods (see demo video).

RODS – standard or short stroke

Smoothing out the vibes and reducing stress on the motor is the best thing you can do for your Norton. 750cc = 175 grams. 850cc = 185 grams, 920cc = 206 grams and 1007cc = 240 grams. Street bikes are more pleasant to ride and racers have a new advantage.

We have worked with Carrillo Industries to develop a longer, lightweight proprietary rod. Several years of research, design, and negotiation with Carrillo has gone into our new rod’s production. The traditional bronze bushing in the small end of the rod has been eliminated and our .708 diameter pins use DLC (Diamond-Like Carbon Coating). This is on the extreme edge of racing NASCAR technology, as the tremendous loads these racers subject their engines to (9000 rpm for 600 miles of practice and racing) will deform and wear out the bronze bushings. Coating pins and eliminating the bushing solves this problem and is the only way to get a more dependable yet lighter weight steel rod. I have personally tested these rods beyond 8000RPM. Our new bushless 6.4″ length rod weighs only 105 grams on the small end (the end that causes vibration. The Ultra light rod weighs only 95 grams on the small end. The CARR bolts are the highest quality and do not need replacing for the life of the rod (if not overtightened). Use original style shell bearings. Balancing is not required for Commando engines (BALANCE INFO). Use stock ignition timing (COMPARE WEIGHTS).

MORE POWER, LESS STRESS

Our custom Norton rods for standard 89mm stroke are 6.400″ long (.525″ longer than stock) and increase the rod-to-stroke ratio from 1.67 to 1 (stock) to a more ideal ratio of 1.83 to 1. Our short stroke rods for 80.4mm stroke are 6.57″ long and give you an ideal 2 to 1 rod stroke ratio. The advantages of a longer rod are:

A) More power: The increase in power is a result of more dwell time at the top of the compression stroke, allowing more time for the fuel charge to burn completely and exert maximum force on the piston throughout the power stroke, This translates to more power for the amount of fuel you burn.

B) Less Vibration: More dwell time at the top and bottom of the piston strokes means less “snap” due to the pistons not having to stop and reverse direction as quickly and abruptly as they would with a shorter rod. The longer rod slows down the piston speed at mid stroke so there is less piston acceleration and de-acceleration. Wear is reduced and we can make the piston shorter and lighter.

C) Less stressful wear: The longer JS rod has less angle when traveling through mid-stroke than the short stock length rod. This means that less side forces are being applied to the cylinder wall – thus reducing friction, heat and wear.

Reducing stress is very important for Nortons as they have a tendency break cranks & cases and vibrate everything to pieces. Our longer rod also reduces the side pressure that the piston exerts on the cylinder, causing power-robbing friction, and because of this helps the engine to run cooler and more efficiently.

ROD RATIOS
Norton 750/850 5.875” rod with 89mm/3.5” stroke = 1.67 to 1 ratio
Norton JS long 6.4” rod with 89mm/3.5” stroke = 1.83 to 1 ratio
Triumph 650 6.5” rod with 82mm/3.23” stroke = 2 to 1 ratio
Triumph 750 6” rod with 82mm/3.23” stroke = 1.86 to 1 ratio
BSA 650 6” rod with 74mm/2.91” stroke = 2 to 1 ratio
Harley XR 750 6.4” rod with 76mm/2.98” stroke = 2.16 to 1 ratio
Modern F1 race bikes use rod ratios between 2.2 and 2.8 to 1
Note that the stock Norton has the lowest rod stroke ratio listed. Even the JS 6.4” long rod ratio is still lower than all the others except the stock Norton but its a big step in the right direction.

Image below shows how a longer rod reduces piston side loads

Flat top pistons for street and racing

If you want a tight installation clearance then you must have us coat your pistons to avoid scuffing.