Norton Commando Cylinder Head Removal
Removing the cylinder head on a Norton Commando is a long, laborious task, but it's a good way to get to know your motorcycle!
Getting Started
There's quite a few things in the way that need to be removed. There was no fuel in the gas tank, so I didn't have to drain it out.
After the fuel lines to the carbs were removed, the gas tank was unbolted and set aside.
The electrical system on this 1974 850 Roadster was original and cut/hacked in about a dozen spots, so it will not be re-used. Along with the wiring harness, the two coils were removed.
A spanner is required to remove the two finned exhaust pipe nuts from cylinder head.
Some models may have locking tab washers, which need to be bent bent in order to remove.
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Next up was removing the carburetors and manifolds.
To remove the hard-to-get-to Allen bolts that hold the intake manifolds on, an Allen key was cut down for more swing room.
The original air filter box was missing, which saved me the bother of disconnecting it.
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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'.
To avoid confusion, I'm adopting the same nomenclature that the Norton factory service manual uses. Removing the head steady is straightforward.
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Finding Top Dead Center
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.
Set Engine To TDC
When the engine is at top dead center, the push rods are engaging the valves. Once all the head bolts are removed, this will put a bit of pressure on the head and help lift it off the barrel.
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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.
The upper rocker feed bolts require a 5/8 Whitworth socket to remove. As a rule, the alloy washers do not get re-used.
Rocker oil feed pipe on bottom back of timing cover requires a 5/16 Whitworth socket.
After the head-steady and rocker oil feed lines, the intake rocker cover and two exhaust rocker covers can be removed.
At this point, the cylinder head fasteners were sprayed several times with WD40, then allowed to soak overnight.
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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.
At a minimum, you'll need a set of Whitworth sockets.
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.
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.
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.
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.
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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.
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.
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.
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.
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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.
Before and after cylinder head cleaning.
Read: Clean Carbon Off Cylinder Heads
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