Classic Motorcycle Build

Norton Commando Cylinder Head Removal

Removing the cylinder head from a Norton Commando is a long, laborious task, but it's a good way to get to know your motorcycle!

Norton Commando 850 Roadster

During the disassembly process, many pictures were taken, as well as notes written down in a notebook, as to keep track of what went where.

Getting Started

There's quite a few things in the way that need to be removed.

top end of Norton Commando 850 engine

There was no fuel in the gas tank when I bought this project motorcycle, so I didn't have to drain it out. The exhaust system had already been removed.

After the fuel lines to the carbs were removed, the gas tank was unbolted and set aside.

motorcycle gas tank bare metal

The electrical system was original and cut/hacked in about a dozen spots, so it will replaced.

1974 Commando wiring harness removal

Along with the wiring harness, the two coils were removed.

The original air filter box was missing, which saved me the bother of disconnecting it. Next up was removing the carbs and manifolds.

Amal Carburetors 850 Commando

To remove the hard-to-get-to Allen bolts that hold the intake manifolds on, I cut down an Allen key for more swing room.


British Bike Nomenclature

The bike is British, and I'm American, and we call some parts different names. For example, what we would call a top engine mount, the Brits call a 'head steady'.

Norton Commando cylinder head removal

To avoid confusion, I'm adopting the same nomenclature that the Norton factory service manual uses.


Set Engine To Top Dead Center

When the engine is at TDC, the push rods are engaging the valves. Once all the head bolts are removed, this will put a bit of pressure on the head to lift up off the barrel.

Finding TDC

With the spark plugs out, slowly move the kick pedal to get the pistons at top dead center. You can look down the plug hole with a flashlight to see if the piston is at the top of it's stroke (TDC).

Another way to find TDC is to stick a screwdriver in the plug hole and watch it rise with the piston, but care must be taken that it doesn't get stuck and scratch the bore surface.

Oil Feed Lines

The rocker oil feed lines (both sides) were unbolted after the engine was set to TDC. This way, oil doesn't drip out of the open cylinder head holes while turning the engine over.

Norton Commando rocker oil feed lines

Rocker feed bolts require a 5/8 Whitworth socket to remove. As a rule, the alloy washers do not get re-used.

cylinder head removal 850 CDO

After the head-steady and rocker oil feed lines, the intake rocker cover and two exhaust rocker covers were removed.

At this point, the cylinder head fasteners were sprayed several times with WD40, then allowed to soak overnight.


Tools Needed To Remove Head

There are a total of 10 nuts and bolts holding the cylinder head to the cylinder barrels. They are positioned on top front and sides, inverted front, and behind the cylinder.

head bolt sequence Norton Commando

At a minimum, you'll need a set of Whitworth sockets.

King Dick socket set

To get the recessed front bolts (#'s 9 and 10), a 1/4 WW socket is needed. The socket has to have an O.D. thin enough to fit into the bolt hole openings, which are .811 of an inch.

The inverted head bolts under the exhaust ports (#'s 7 and 8) take a 3/16 WW socket from 1971 up. Pre '71 they are 1/4 WW.

It would have been nice to have the special 1/4 Whitworth box spanner for the rear nut (#2). The price of the tool wasn't bad, but the closest one I could find was 3,800 miles away in England, and I'm in North Carolina, USA.

Norton Commando head removal

So, to remove the rear nut, I took a cheap 13mm wrench, opened it up a bit with a 3" grinding wheel, then ground the front and back to make it thin enough to fit between the fins.

Norton Commando head removal

It was ugly, but it worked.

The last bolt to be removed (#1) also requires a 1/4 WW socket.

Cylinder Head Fasteners

CAUTION: The number one cause of fins being broken is trying to force a head off. Make sure you have all 10 nuts and bolts off and accounted for before trying to remove the head.

Norton Commando cylinder head fasteners

Four bolts on top of head (two on either side).

Two nuts on top/front in crevices.

One nut below rear of head (not shown in picture).

Two inverted 'barrel' nuts in front, behind fins facing up.

One bolt top middle, remove last.


Removing Head From Cylinder Barrel

After the all the nuts and bolts are unfastened and accounted for, the head will lift up, but will not clear the cylinder barrels due to the length of the push rods.

Norton Commando cylinder head removal

There are (at least) two methods to overcome this.

Method 1) Push the push rods up into the head. A third hand is helpful here.

Method 2) Remove the front Isolastic mount and drop the motor down. This will give a few extra inches for the head to clear the frame.

Norton Commando remove rocker arms

What I did was, remove the front (intake) rocker arms, which allowed more room to push the push rods up and out of the way.

remove rocker arms from head Norton 850

If you decide to take the rocker arms out, make sure that the plain washer and spring washer come out with the arm and spindle.


Cleaning cylinder heads can still be effectively done by hand, using a spray or liquid degreaser. It will take longer than modern methods, but results will be the same.

how to clean carbon off motorcycle head

Before and after cylinder head cleaning.

DIY motorcycle cylinder head cleaning

Read: Clean Carbon Off Cylinder Heads


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