Norton Service Release Database N11

SERVICE RELEASE N11

NATURE OF RELEASE: Method of shimming Isolastic Mountings with the power unit in the Frame MODELS AFFECTED: All Commando PARTS AFFECTED: Front and rear engine mountings DISTRIBUTION: Worldwide EXPLANATION: It is essential for the Commando power unit to be free on its mountings with clearance all round to prevent vibration. Similarly it is essential for freedom of movement to be controlled to close limits since the swinging arm is mounted on the rear engine plates and thus excessive side play would result in poor handling. Side movement is controlled by the use of shims fitted between the tube cap and spacer tube. Such shims are available in thicknesses .005 in. , .010 in., .020 in., .030 in. On the all-rubber mountings used from early 1969 onwards, the ideal shimming would be to produce . 005"in. Free movement at both sides of the front and rear mountings with clearance all round the end collars. Manufacturing tolerances however may make it necessary to increase the free movement in individual cases to prevent transmission vibration. Under no circumstances should the mountings be assembled with nil clearances.   ACTION: Before attempting adjustment with the unit in the frame, you should have available spare shims, a torque wrench, spanners for the mounting bolts, a long bar to lift the power unit in the frame, a soft metal drift and a long slave bolt. Slide basic the plastic gaiters in turn and check free play with a feeler gauge between the polyurethane washer and end collar at each side. Record the measurements. Starting with the front mounting, remove the nut and, using the soft drift, tap the mounting bolt through until the gaiter, collar, polyurathane washer, tube cap and shims can be collected. Now slide the slave bolt into the mounting to support the unit as the mounting bolt is pulled free. Collect the gaiter, collar, shims etc., from this side then repeat for the othor side. Measure the total thickness of shims used in the front mounting, subtract this from the gap checked before dismantling then select shims to permit an ideal of . 005"in. clearance at each side. Divide the shims selected between the left and right sides, smear the shims with grease and than reassemble ensuring that the plastic gaiters are not too long so that they are trapped between the frame lugs and end collars. The gaiters may be triauncd carefully with a very sharp knife if necessary but do not remove excessive material or water and dirt ingress will occur. Note that tho spindle nut must be torqued to 25 foot pounds. Now check that at no point is the collar hard on the mounting tube end cap. If it is, then remove shims a little at a time until there is clearance ALL ROUND. Check and rectify the rear mounting shimming by the same method untii again there is free play all round. On the rear mounting it is even more important to allow no more free play than is absolutely necessary to achieve all round clearance. June 1970 Norton Villier Canada Limited