Norton Commando Timing Cover Removal and Installation
Text and Pictures by Mark Trotta
Next up on the Commando engine teardown is timing cover removal. There are 12 screws holding the cover on, but several other items need to be removed as well.
Early vs Late Timing Covers
The first Commando engines (1968/1969 with engine prefix 20M3) have a different timing cover than later models. These early 750 engines have their ignition points in a distributor housing and there was an external rev-counter drive.
The 'camshaft points' timing cover, as pictured in this article, was fitted from the 750cc 20M3S engine (around 1969) and up through all 850 models. There are two sets of contact breakers (points) behind the round cover.
Removal and installation of early and late covers are similar.
Getting Started
Exhaust pipes had already been taken off during cylinder head removal.
On 1974 and earlier Commando models, the right-side shift pedal gets removed. Later models may require brake pedal removal.
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Timing Cover and Breaker Plate Removal
The two bolts that hold the contact breaker cover (points cover) are removed with a flat-blade screwdriver.
Underneath the points cover, there are two studs holding on a breaker points plate.
The breaker points studs have a head size of 8.23mm (.324"), so neither a metric or standard socket will fit correctly. The correct size is a 2BA Whitworth.
In the center of the points plate is the cam center bolt, which has a head size of 11.4mm (or .45"). The correct socket size to use is 3/16 Whitworth.
Read: What Are Whitworth Tools?
CAUTION: Be very careful with the cam center bolt, it threads into the camshaft!
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Remove Ignition Rotor
The ignition rotor (breaker cam) is a light press fit into the case. It gets removed before the cover comes off.
The factory service manual calls for a specialty tool (06-4298 slide hammer) to remove the rotor. For those interested in buying one, this tool also removes rocker spindles from the cylinder head.
As an alternative to buying the special tool, I adapted my body shop slide hammer to accommodate a 5/16-24 bolt, which was then threaded into the breaker cam.
A single soft rap of the weight removed the breaker cam.
TIP: While removing old parts, use a penetrating fluid (like WD40) and allow time to soak.
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Oil Feed Pipe
On the bottom rear of timing cover, there is a bolt which holds the rocker oil feed pipe. The head measures 15.2mm (or .62") so neither metric or standard sockets will fit correctly. The proper size socket is a 5/16 Whitworth.
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Commando Timing Cover Bolts
The 12 bolts have three different lengths; 1", 1-1/8", and 1-1/4".
An easy way of keeping track of which bolt goes where - punch holes in a piece of cardboard.
Factory bolts had a flat-blade head, but for those unconcerned with originality, Allen head bolts are a nice upgrade.
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Wire Harness
If you haven't done so already, disconnect the two contact breaker leads.
TIP: Draw the bullet snap connectors through the the cover one at a time.
If the cover doesn't come off, make sure you removed all 12 bolts. Sometimes, the gasket sticks to the crankcase, so you may need to work it free. Try a little gentile persuasion with a gasket scraper and plastic mallet.
Inside the cover is casting number 06-1072. This is not the part number. The part-number is 06-6161.
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Polishing The Cover
To me, this was the fun part!
First, a few deep grooves were filed out, then cover was completely sanded with 80 grit Emory cloth.
Next was 120 Grit Emory cloth.
Then sanding the cover with 240 wet sandpaper.
More wet sanding with 400, 600, and 1000 grit paper, then over to the buffing wheel.
Read: How To Polish Aluminum Engine Parts
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Timing Cover Installation
Before re-installing the timing cover, check that all three alignment dots (crank pinion, intermediate pinion and camshaft pinion) are properly spaced.
NOTE: There are differences in the thickness of different brands of timing cover gaskets. The correct one is included when you buy a complete engine gasket set from Andover Norton.
Check that you have the rubber seal on the oil pump before re-installing cover. There is a service tool to protect the new seal during reinstallation.
Before applying any gasket sealer, push the cover up with gasket in place. Remember that the oil pump conical seal needs to be compressed.
Once the ignition rotor is back in, the static timing needs to be checked.
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