| Number | Nature | Explanation | Action |
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N1/01
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Kickstart foul on right exhaust pipe.
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An alteration has been introduced onto the muffler bracket to provide adequate kickstart pedal operating clearance.
The new bracket, which should only be fitted to the right hand side pipe is supplied under part number 063579.
Alternatively the existing right hand bracket may be re-formed as indicated below.
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N1/02
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Alternative hydraulic hose lengths (disc brake)
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It has been decided to make available alternative lengths of brake hose which can be ordered by distributors and made available at their discretion. Below are listed all the available hydraulic brake hoses with part numbers and lengths:
Standard hose 062707 Length 25in.
Alternatives
063508 23in.
063507 28in.
063541 31in.
063540 34in.
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Where disc braked Commando models are equipped with alternative heights of handlebar, select the most suitable hose length from the list above.
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N1/03
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Availability of quartz halogen light units.
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Quartz halogen light units are now available as a kit through the Spares Department to convert existing headlamp units. The conversion is available only for 7in. diameter headlamps and thus cannot be incorporated on Hi-Rider and SS models. The conversion kits available are:
Left hand dip set comprising:
54526114 Light unit
463 Bulb
553738 Bulb holder adaptor
Right hand dip set comprising:
54526323 Light unit
472 Bulb
553738 Bulb holder adaptor
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Where quartz halogen light units are legally acceptable for your market, order the requisite number of conversion kits as normal spares requirements.
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N1/04
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Reproduction
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To avoid production delays a Factory policy decision has been taken that in future main Distributors will be responsible for the reproduction and distribution of Service Releases. This will be done from text and, where necessary, artwork supplied from the Factory. The Factory will furnish main distributors with bulk supplies of headed paper to aid reproduction locally.
The reproduction method adopted is left to the distributor's discretion, dependent upon the length of his mailing list. It is most important to retain the Factory number sequence.
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Advise Technical Department Wolverhampton, England, of the quantity of Service Release headings required and periodically call up further quantities as necessary.
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N2/01
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Modification to exhaust valve guides.
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The design of exhaust valve guide NMT2011 has been revised to prevent excessive oil passage between the valves and guides. The upper end of the guide has been shortened so that the taper on the valve stem cannot enter the neck of the guide which would cause a pumping action. To avoid reducing the supporting length of the guide, the lower end of the guide has been lengthened by a similar amount. The modified valve guide is being supplied against part number 063527, and as stocks are exhausted, the later guide will supersede the earlier type directly
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Until dealer stocks of the taller guide are exhausted, ensure where possible that exhaust valve guides are used in pairs.
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N2/02
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Clutch plate oil disposal grooves.
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The clutch friction plate 061339 now incorporates scrolled oil dispersal grooves on both sides. The friction plates shown in the Parts List incorporate such grooves but this modification was not in fact effective during the1971season. The purpose of the grooves is to disperse oil which can otherwise cause clutch slip. Factory stocks of friction plate 061339 have had the oil dispersal groove added so that future supplies will be to the latest design. It is not necessary to return dealer stocks to the factory but in cases where clutch slip can be attributed to oil on the plates, the modification detailed in Service Release N5 should be carried out.
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N2/03
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Combat valve springs.
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On certain Combat engines from the initial production batch, we have become aware of a condition which prevents the valves opening sufficiently
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At the first service or first convenient opportunity, check that the valve springs are not preventing the valves opening fully. With the fuel tank and rocker covers removed, turn the engine until any valve is opened fully, i. e. is depressed into the cylinder as far as permitted by the valve operating gear. At this stage push down the rocker adjuster against the valve stem, such as with an aluminium or wooden shaft, and ensure that the valve can move perceptibly as the spring is depressed further. Repeat this check on all valves in turn. Perceptible movement indicates that all is well but a lack of movement will necessitate the use of a new thinner bottom valve spring cup part number 063996 The thinner bottom cup is identified by the marking "IN" on the inner facing. As an alternative to using new cups, the NMT2073 may be reduced in thickness to 0.065in . (1.65mm).
The above check applies only to engine number series 200004 to 202340.Thin bottom valve spring cup washers 063396 were fitted from 2023 >>>
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N2/04
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Combat and standard Commando
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In order to meet early 1972 production requirements, an interim piston has been produced to accommodate the additional valve lift of the Combat engine, As the new interim Combat pistons differ only from the previous Commando type in the depth of the valve cutaways, the new pistons are therefore currently specified for both standard Commando and Combat versions and supersede the previous pistons 062459(L.H.) and 062462(R.H.). When the final Combat pistons become available, they will be of the solid skirt variety and completely interchangeable with the interim Combat pistons (though, ideally, in pairs). The part numbers of the various pistons are detailed below:
Incoming orders for solid skirt pistons will be fulfilled from interim version stocks until the changeover is completed. Note that on a production basis interim pistons were introduced from engine number 200976 and final Combat pistons from engine number 204166.
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N2/05
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Introduction of disc-brake conversison kit.
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We have received a considerable number of enquiries for the parts necessary to incorporate the new Norton-Lockheed hydraulically operated disc brake on a Commando previously equipped with the cable operated drum brake. In view of this interest, we have introduced a disc brake conversion kit under part number 063412 which incorporates all the parts needed for this conversion. The kit is offered at a very attractive price and the following list shows the parts incorporated in the kit which is in the form of a cartoned semi-display pack:
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N2/06
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Crankshaft Main Bearings.
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Field experience with 1972 models (incorporating two single lipped roller main bearings) indicates a small, but significant premature roller main bearing failure rate.
Reported failures have been confined solely to one type of bearing.
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When replacing defective roller main bearings, ensure the replacement is a Skefco double lipped outer, single lipped inner spool type NJ306, with a specified nominal internal diametral clearance of 0.0008/0.0012ins. (0.02/0.03mm) Prior to fitting (180 Normal).
Ensure the crankshaft journals are carefully cleaned up, removing all signs of butts or scoring before fitting the inner spool. Models subsequent to Engine Number 207197 incorporate a nominal increase in bearing housing diameter to overcome any significant tendency to excessive closure of the single lipped outer series of roller bearings.
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