Motor and Transmission
This is the break down on the heart of the bike. There’s a fair amount of detail and its all to the point… So lets get to the facts!
Cases: Steve Maney racing cases that are beefed up all over to eliminate the common weaknesses found in stock Norton Commando cases, such as cracking on the drive side bearing boss. The cases were machined to accept the Colorado Norton Works breather setup, which virtually eliminates leaking on Norton motors by creating negative pressure in the crankcases.
Crank: Crank is a Steve Maney lightweight crank with standard 89mm stroke and a balance factor of 72% WET, balanced at Lindskog Balancing in Massachusetts. Kenny has tried balance factors from 84% down to 60%, and settled on a low to mid 70s range for a Seeley MK2 application. According to Kenny, the bike feels better than any rigid mounted Seeley that he has ridden yet. Crank has a 3/4″ threaded hole at exactly BDC allowing a mallory slug to be threaded in through the sump plug, thus being able to change the balance factor while testing without having to tear down, or even remove the motor.
Rods: JS Motorsport custom long rod/raised piston pin setup. These rods are made by Carrillo to JS Motorsport specs. The advent of the longer rod and raised piston pin brings the motor closer to desirable 2:1 rod/stroke ratio. This helps reduce the “snap” at the top and bottom of the stroke resulting in less friction, vibration, and stress on all bottom end components, thus increasing HP and life of the motor. To save weight, on the small-end the rods do not have a traditional bronze bushing, but instead use DLC (Diamond-Like Coated) wrist pins.
Pistons: JS Motorsport custom pistons, made by JE to JS Motorsport specifications to the original bore of 73mm. They weigh 1/3 less than stock which greatly reduces vibration in the motor. Compression is 11.5:1, with a squish band clearance of .035″ machined into the sides of the pistons. Pistons have reliefs cut out for valves (valve pockets) with approx .065″ piston to valve clearance. Cylinders were machined with .005″ piston-to-wall clearance. The pistons also have “gapless” rings which reduces blowby and increases HP and prevents heat & corrosive gases from entering the crankcase.
Cylinders: Steve Maney lightweight alloy cylinders. These cylinders weigh almost 12lbs less than standard Norton Commando barrels. The barrels are 850cc bore that are sleeved down to 750. The reason for this is it allows us to run an 850cc head, which has a wider bolt pattern than 750 heads and allows more room for overbores, etc.
Head: Fullauto Technologies 850cc head with 33mm inlet ports that open up into a world of black magic, and D-shaped exhaust ports. Off the shelf, these heads flow immensely better than a stock Commando head (FYI – my bike’s head is an off-the-shelf Fullauto). This particular has had additional porting by Jim Comstock of Comstock Engineering (the person who did the original port design on all the Fullauto Norton heads). The flow bench numbers put it in line with a Steve Maney Stage 3 head, all without all the Stage 3 big valve fuss and valve re-angling necessary for Maney to get good flow.
Head Gasket: JS Motorsport very thin (.003″ ) head gasket and helps bump your compression up without having to mill your head or special order taller pistons. This head gasket is very reliable when properly installed – plus it is re-usable. It requires a special silk string technique to prevent oil leaks.
Cam: Cam is a JS Motorsport Stage 2 cam, with high lift (410 lift) and similar to a Norvil 4s or Megacycle 560NSS race cam. It’s lumpy and badass. The cams requires a special design to run with the radius surface of the BSA lifter. The radius design also provides a much greater lifespan.
Valve Train: BSA-Triple-Style bronze tappet blocks with highly radiused BSA lifters (necessary for high-lift cam). The BSA lifters are 1/3 the weight of the Norton part decreasing valve float and increasing max RPM to take advantage of the lighter rod/piston. The lifters are moving custom alloy pushrods, lightened rockers, alloy adjusters, and custom Kibblewhite DLC coated valves machined by Comstock Engineering to enhance flow numbers. Beehive springs are used with titanium collets and keepers. The springs weight 1/2 as much as other racing valve springs and are slightly stronger. The top of the spring is smaller in diameter in order to avoid unwanted harmonics and this allows for a smaller retainer which again saves weight. There is no comparison to older designs. The entire valve train is available from JS Motorsport.
Trans: TT Industries magnesium 6-speed drum-selector cassette-style gearbox in AMC (stock Norton) style shell, with close gear ratios hand-selected by Kenny that work best with the powerband of a tuned Norton Commando racing motor. We purposely kept 1st gear low (many close ratio boxes have a very tall 1st gear) because with 6 speeds we would have plenty of options for gearing, and will hopefully never have to get back to 1st gear after the launch at the start. So with a low 1st we can get good starts and then work our way up and down from 2nd to 6th during our “relatively” short races. Kenny has ridden on many bikes with different gearboxes, and this box, without question, is the best in the world for a vintage racing motorbike. 19-tooth countershaft sprocket mounted.
Primary: Steve Maney Belt Drive with a 38-tooth front pulley and 70-tooth lightweight clutch basket, using 920 length 8mm pitch 40mm width HTD belt.
Clutch: Stock Norton Commando diaphragm spring clutch, with 5 Barnett friction and 5 stock steel plates. The good old Commando diaphragm clutch is one of the best there is.
Ignition: This topic is still under debate as we are still testing. The ignition on the bike is a Power Arc, with 2 available curves. These curves can be programmed into the bike by Old Britts, and we will be making some of our own custom maps specific to racing. Right now we are using the “aggressive” curve, as opposed to the “street” curve. There is a trigger wire on the ignition which allows the curves to be switched on and off, however, this feature is not used as switchable curves are not allowed in vintage racing. The other option is going with an old school Boyer.
Plugs: Denso IW-27 racing plugs. Colder than stock, naturally.
Battery: We are running a total-loss setup with an Antigravity 4600 lithium battery 4.6amps per hour), which weighs under 2lbs and is tiny.
Carbs: Carbs are Amal MK2 racing carbs with built-in velocity stacks.
Carb bore = 36mm
Slide = 3 (2036 marked on slide)
Needle = 2A1
Clip position = 2 of 5 (2nd from top)
Needle jet = 106
Main Jet = 300
Pilot = 25
Throttle: Tomaselli Twin-Pull – the best… in fancy chrome.
Tach: Scitsu Racing Tacho, reads up to 10k
That’s it. Simple right!?