Norton Commando Workshop Manual

## Engine/Primary Transmission

# C

### SECTION C41

### CHAINS

It is important to maintain the correct chain tension since if the chain is too tight the engine and gearbox bearings will be pre loaded in the case of the primary chain and the gearbox and rear wheel bearings will be pre loaded in the case of the rear chain. Pre-loading will inevitably cause premature bearing failure. Conversely, if the chains are too slack then premature wear is inevitable on the sprocket teeth.

The primary chain operates in an oil bath formed by the primary chaincase and requires no lubrication from an outside source providing the chaincase level is maintained. The rear chain is lubricated automatically from the oil tank via a restrictor located to the rear of the tank. However, the rear chain is not fully enclosed and from time to time requires cleaning and lubricating manually.

Chain Serviceability
Both in the case of single row (rear) chain and triple row (primary) chain, chain length extention of 2% is permissible before the chain is considered to have reached the end of its usefulness. This figure presumes that extension is checked only when the chain has been cleaned thoroughly and that any chain showing evidence of broken rollers has been discarded.
Primary Chain Adjustment
The separate gearbox design of the Commando permits adjustment by the medium of pivoting the gearbox on the bottom bolt and there is no necessity for a slipper type tensioner. Due to the high power output of the Commando and Combat engines the correct adjustment procedure must be followed to prevent subsequent gearbox movement in service. Proceed as follows:
1 | Check the total up and down movement on the primary chain top run. This is felt by the finger when the upper centre inspection cap is removed from the chaincase. If incorrect, proceed to (2).
2 | Slacken the gearbox top fixing bolt "B" |(see Fig. C48). Note that nut on left is captive and must not be turned.
3 | Slacken the nut on the gearbox bottom bolt.

4 | Slacken the front nut on the adjuster eyebolt, two or three turns.
5 | Tighten the rear nut on the adjuster eyebolt until, with the finger, the chain can be felt dead tight.
6 | Now slacken off the rear nut and carefully tighten the forward nut until there is total up and down movement of 3/8 in. (9.5 mm).
7 | Tighten securely the rear nut to lock the assembly and recheck the adjustment in at least three places. Should there prove to be a tight spot, readjust to total up and down movement of 3/8 in. (9.5 mm) at this point.
8 | Tighten the gearbox bottom bolt nut. Lubricate the thread of the gearbox top mounting bolt, fit the nut and secure to 70 Ib. ft. (87 in. Ib., 9.678 kgms.) torque from the right side. Note: On 1972 and later models, do not attempt to turn the nut at the left side of the top bolt - this is spigotted to prevent movement.

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