Q & A

I thought I’d ask Kenny a few questions about our Seeley Norton:

To start with, why Norton?

For me, I have always been drawn to Nortons.  My father had a Norton.  I remember seeing that logo when I was a boy.  It’s been with me for a long time.  But beyond this, the name has always been synonymous with racing success in the golden years of Grand Prix.  For our current vintage racing bikes, the spares and performance mods available for Norton motors are some of the best out there.

Why a Seeley chassis?

I will answer this from my own personal perspective:  I started racing on a Featherbed with a Commando motor within.  I did this because I’d seen others do it with success.  I won my first championship on that bike, but as I got faster and pushed the bike harder, the frame began cracking at almost every event.  It was a major problem to have to tear the bike down and weld between races.  About this time I took a lap on a friend’s Seeley MK4 and was completely amazed at how nimble this bike was.  After some discussions with Steve Maney, who has done very well on his own MK2 Commandos, I decided to try out the MK2 chassis; a cradle frame like the Featherbed, but a true GP frame.  There is a lot to be said for running a chassis that is purpose-built for racing (my Featherbed was a mild-steel road-going frame).  The geometry of the Seeley is very nimble, the bike tracks perfectly straight and stable, it’s low and lithe, and light!  It was the state of the art in its day, and for good reason.  I’m not taking away from the Featherbed, the Manx Featherbeds were the benchmark for racing chassis in their day, but I find the Seeleys to be lower and tighter, and perfect for our short-circuit tracks.

How is  the motor different than stock?

The motor is set up for racing, so almost everything is different, from the lightweight crank (almost 12 lbs lighter than stock),  balance factor (stock Commando was 52%, yours is 72% WET), to the long rod/raised piston setup, extremely different head port design, aluminum cylinders, etc.  Stock 750 Commando compression was about 9:1, you are at 11.5:1  Your valve train is significantly lighter than stock, and your entire motor is blueprinted.

What machining was done to the motor?

All clearances were spec’d, squish band is set to .035″, so pistons had to have the squish band ring turned into the edge.  Some additional pocketing to the pistons was necessary to accommodate the high lift of the cam.  The cases were machined on the rear to accommodate the CNW breather.

How was it balanced?

The crank was dynamically balanced by Lindskog Balancing in Boxboro, MA. They are the best in the country for this type of thing.  I set the balance factor at what I knew worked and complimented the JS Motorsport piston/rod setup.  Much back and forth has been discussed between myself and JS Motorsport, Comstock Engineering, Steve Maney, and Lindskog to be sure we got the balance factor as best as possible for your bike’s intended application (which is going fast and keeping the revs between 5500 and 7500rpm)

How was the head flowed?

The head was flowed by Jim Comstock of Comstock Engineering, who was the initial designer of the Fullauto head combustion chamber.  In the initial stages of your motor discussions, Comstock and I agreed that we would run an 850 head and barrels (sleeved down to 750) because the 850 heads have a wider head-bolt spacing, thus allowing overbores down the road if necessary (for example, AHRMA allows +.060″ overbore on 750 twins, which would put your max allowable bore to 74.5mm – too wide for a standard 750 head bolt patter as the holes begin to interfere with the head gasket.  Your head has had extensive flowing beyond the “off-the-shelf” Fullauto head, bringing its flow bench numbers up to par with much more elaborate big-valve heads that require extensive machining and custom parts.

What parts are stock?

All of the timing gears, timing chain, seals, oil pump, pinion gear, etc, are stock Norton Commando – the same bits you’d have on a road-going street bike.  Your valve rockers are stock.  Your front wheel hub is a Norvil twin-disk racing hub, which is not stock in the sense it was mass-produced for Commando street bikes, but it is a genuine reproduction of what was run back in the day by the factory Norton race teams.  Diaphragm spring Commando clutch is stock.


I keep the redline at 7500rpm.  Although with your cam you may be making power beyond that, for safety reasons it’s best to use the great torque of the motor and not blow it up.  I have pushed my own bike to 8k on numerous occasions when it was in the heat of battle and just not a convenient time to shift, but I don’t like doing it.

About how much power?

I find a racer doesn’t want to give this stuff away, and it’s so subjective anyway.  Many people think a Norton race bike should be putting out 85-90hp, but they’re absolutely tripping.  In fact, if we get +70hp out of your bike we’ll be in fantastic shape.  I’ve ridden your bike, and I know it’s fast.   Just leave it at that.

How many race weekends before the motor needs to be torn down?

I can usually get a season out of a motor without having to completely tear it down, but often there are tweaks, etc, which will have the motor out of the bike in some capacity during the season, so let’s just say it’s a “fluid situation”.  I retorque the head and adjust the valves before each event, and often will make some minor change here or there.  Oil changes are done after each long weekend, or at maximum, after 2 full weekends.  At the end of the season I take the motor out and go through it all, looking at piston wear, cylinder wear, cam and tappet wear,and replacing or repairing the necessary components.  I change the main bearings and big-end bearing shells as a matter of course.  Until recently our first big event on the season’s calendar was Daytona, which made for some interesting motor break-ins, to say the least.  Fortunately Daytona is now at the end of the schedule, so a less severe break-in process can be achieved by doing a couple of gentle practice sessions or track days before the first racing event.

If this bike ran in a period race, how would it fair?

Hmmmm.  Make no mistake, folks were getting good handling and power out of their racebikes in the late ’60s/early ’70s, but we would have the advantage of better metalurgy and technology (at least in the flow-bench porting and dyno tuning, etc).  Since a lot of my NYC Norton-built bikes use aftermarket cases, cylinders etc, we have modified castings and lighter/stronger components that weren’t available in the day, which allows us to push the bikes harder without the risk of catastrophic failure.  This is a delicate subject to me, and many others.  I love the bikes I build and race, but I do believe there are distinct advantages to our bikes that push us outside the boundaries of someone running a bone-stock bike from the period.  I am glad our vintage organizations (usually) recognize this and have created specific classes for stock, original bikes, and other classes for our radical built “prototypes”.

How do you rank the seeley against other vintage race brands?

The REV’IT! Seeley is truly a Formula 750 race bike.  This means it goes up against some of the baddest bikes currently racing out there, including one very fast Triumph, and a couple of stunning Harleys that are getting big power to the back wheel.  With the right rider and conditions the Seeley can out-maneuver all of them due to its nimble character and stability.  There…  I said it!