Norton Service Release Database N3/10

SERVICE RELEASE N3/10

NATURE OF RELEASE: Isolastic mounting shimming MODELS AFFECTED: All Commando DISTRIBUTION: Worldwide (general distribution) EXPLANATION: Service Release N11 of June 1970 laid down a method of shimming Isolastic engine mountings. The method recommended produces satisfactory results but due to varying techniques worldwide, one particular method of shimming has been tested widely and has been approved by the Factory Engineering and Development departments. This will now become the sole method used by all Factory service personnel and, by all concerned with assembly and servicing of the Commando. During shimming, support pre-1971 models on the centre stand but 1971 and later models on a strong box placed beneath the main frame tubes, to relieve tension on the mountings. The recommended ideal clearance from this time, both front and rear, is 0. 010in. Shims are available in thicknesses of .005in., . 010in., .020in., .030in. Where possible, avoid the use of the thinnest shims which tend to disintegrate after prolonged use, but where proven to be absolutely essential - ALWAYS ENSURE the thinner shims are fitted first onto the tube cap, the thicker shims bearing the load against the mounting tube end. Check the mounting clearance and record the figure prior to re-shimming. Also, it is advisable to renew the polyeurathene washers on both sides of each mounting to maintain engine symmetry, whenever re-shimming proves to be necessary after the first 10, 000 miles.   ACTION: Check existing shimming as follows: Front mounting - Slide left side gaiter back to give access to the shims and polyurethane washer. Insert feeler gauges as required between the tube cap and polyurethane washer and record the clearance. Rear mounting - Slide the right side gaiter back to give access to the tube cap and polyurethane washer and record the clearance. Having established that re-shimming is necessary, proceed as below:- Shimming front mounting - Remove the self-locking nut and plain washer from the mounting bolt. Align the flats on the hexagon of the mounting bolt with the timing case casting of the engine. Using a soft metal drift to avoid damaging the threads drive the bolt through sufficiently that the gaiter, collar and polyurethane washer can be removed together. Remove the tube end cap. If at the time of checking, the clearance was found to be, for example, 0. 030in. , then a shim, of 0. 020in. thickness should be added to fit between the end cap counterbore and the end of the-engine mounting tube. Prior to reassembly, clean all the parts including inside the gaiters, and grease lightly using silicone grease RELEASIL No. 7. Examine the polyurethane washer for excessive wear producing uneven thickness and replace if necessary. Reassemble the gaiter, mounting collar and polyurethane washer after attention. Note that the reassembly procedure is a reversal of that used in dismantling but take care to fit the end cap with shims snugly over the actual mounting to allow room for the gaiter, spacing washer and polyurethane washer to be fitted together, Secure the mounting bolt and nut to a torque reading of 25lb. /ft. Shimming rear mounting - Remove the self-locking nut and washer from the right end of the main mounting stud. Using a soft metal drift drive the mounting stud partially through, right to left until it protrudes some 4in. from the left hand side. Slide the right gaiter lip off the mounting tube then push dow May 1972 Norton Villier Canada Limited