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Pistons and Rings

Steve Jowett www1.kingston.net/~fortierg/mainb.htm

Norton Service Release Notes

 
Service Release No. N13
Nature of Release Excessive oil consumption
Models Affected Commando
Distribution Worldwide  
Parts Involved Taper compression rings


Explanation
We are aware of a condition of severe over oiling and previously some improvement has been achieved by the change of scraper ring type and more careful assembly of the scraper rings. However, a certain number of machines have still returned unsatisfactory oil consumption figures. As a result of intensive test rig and road tests, the problem has been pinpointed as a manufacturing discrepancy in the middle (tapered face) piston rings. After consultation with the ring manufacturers, a change in manufacturing techniques will prevent any reoccurence on future rings. To cope with any machines giving trouble in service, a revised form of piston ring is being made available immediately.

Action
On any machine returning an oil consumption figure heavier than 200 miles per pint, replace the middle ring on both pistons with the special ring Part No. 06-2262. It is essential to fit these rings with the word 'top' facing upwards so that proper oil control is gained. This special type of ring is identified by a chamfer on the inner diameter. We are confident that after this rectification the over oiling problem will be overcome.

(July 1970)

 

Service Release No. N46
 Nature of Release Introduction of S.E. piston rings (oil control)
 Models Affected 1971 Commando- all models Engine Nos. 146584 - 147176 and 147259 onwards
 Distribution Worldwide (for general distribution)  


Explanation
Spring expander type oil control rings have been introduced on the motorcycles specified above. The piston bodies are revised to accommodate the spring expander type of ring and for this reason it is not possible to use the later rings on an earlier piston or vice versa. For spares purposes the revised pistons with rings as a pair can be used to advantage on previous Commando models. It is not considered good practice to assemble an engine using one old type and one new type piston. The part numbers of the old and new components are detailed below.

Item Old Number New Number
Piston complete, left hand 061185 062459
Piston complete, right hand 061186 062462
Oil control ring 061180 062461

When replacing pistons or piston rings, ensure that the correct parts are used as detailed.

(June 1971)

 

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