Norton ES2 Engine Work

When the bike first went back on the road in 2014 I was very disappointed with the performance of the engine so I soon set about improving it. It's been through several iterations since and I've been down more than one blind alley. This page will tell you how the bike is set up now as well as a few of the mistakes I made along the way.

Crank Assembly and Crankcases

Standard conrod, big end and flywheels
Balanced to 68%

Barrel and Piston

The first task was to raise the compression ratio a bit. A standard ES2 is about 6.5:1, assuming everything is in good order. A 16H piston can be used to raise this to a around 8.5:1. The pisting needs shortening and valve pockets machining in. Here you can se a standard 16H piston and the one we modified for the ES2.

The 16H piston gives a nice dome to reduce the combustion chamber volume. We also use rubber O-rings to seal the oil returns. This is required after the the barrel and head where machined and ground together to remove the need for a head gasket. I minimal increase to compression but it does stop the head gasket from blowing, a common issue with currently available aluminium head
gaskets.

Why not take a look in our 'Technical' section for a page that goes into more detail on how we modify 16H pistons like we did for my bike.

Modifying Norton Pistons

Cylinder Head

New valves, guides and some cleaning up but no proper porting
Head gasket removal

Valve Timing

Further down the engine we’ve done some experimenting with different cams. Firstly we tried a set of race cams. The bike was used like this for a year or so and even on a 3000mile round trip to Italy and back. Regularly hitting 80mph the ES2 certainly flew, but it was difficult to ride and ‘lumpy’ in traffic so the cams were removed to try another option.

With some more experimenting we found that the ES2 had very lazy valve timing as standard so decided to go back to standard ES2 cams but advance the inlet cam one tooth to give lobe centres closer to what we thought would be optimum. This made a huge difference to the performance and the bike is considerably more enjoyable to ride!

OHV Norton Valve Timing

Although much happier with the ES2 fitted with standard cams and altered valve timing we decided to see if we could take it a step further. We got hold of a set of 16H cams which are a straight swap but offer slightly more lift and duration, without being as extreme as the race cams.

To help fine tune the timing with these cams we had 2 extra keyways cut in a set of timing gears allowing us to set the valve timing in 6° increments instead of the 18° we are stuck with on a standard set up.

This set up gave a significant improvement, once the carburation had been set up to match it, and is still in the engine now.

To help compare some of the cams we have experimented with we have created a technical page on OHV Norton cams which includes a table showing a number of useful comparisons.

Ignition Timing

Experimented with vernier
Not 5/8 (42deg)
Had trouble with it overheating when retarded

Carburettor

Tried bigger but lost torque without gaining much top end
Importance of idle and pilot jet for starting Nortons

We are closed for a weeks holiday!