Norton Camshaft Running In Procedure

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As the maker, there are three things that we can do to help prevent camshaft wear.:-

1. Provide camshafts with a minimum hardness of Rockwell 50.
2. Provide camshafts with the best possible machined finish.
3. Supply profiles that are not overloaded or highly stressed.

The engineer fitting the camshaft has the greatest responsibility for proper running in of the camshaft.  Following the steps described below will insure a long and trouble free life from the camshaft and component parts.

1. Coat the camshaft lobes with micrometer blue and fit the cylinder head and tappets (camfollowers).  Rotate the camshaft.  Remove the cylinder and tappets and check that the tappets are making full contact, if not DO NOT assemble the engine.  Norton cylinder blocks are regularly radially out of position causing point contact of the camshaft and tappets.  If full contact is being made, thoroughly clean the parts, oil and re-assemble.
2. Coat the camshaft lobes and camface of the tappets with camshaft lube.  Camshaft lube is an oil that has been designed especially for the lubrication of camshafts prior to their assembly and must be used when assembling the camshaft and tappets.
3. Check the whole valve train for interference before attempting to start the engine.
4. Before trying to start the engine, adjust the tappet clearances.  Fill the carbs with petrol and check that the timing is correct.  The engine must start right away, a long time turning the engine over may damage the camshaft.
5. Do not let the engine speed drop during the first half hour of running in.  R.P.M MUST be kept at 2500 or above.  Oil lubrication and cooling of the camshaft comes from the crankshaft as well as the oil feed from the exhaust rockers and oil throw off below 2500 R.P.M is not sufficient for running in.  Engines may be run in the workshop, on the road or at the track.  If adjustment must be made during the first half hour running in period, switch the engine off, do not let it idle.
6. Make sure that exhaust rocker spindle feed holes in cylinder head are not obscured or blocked, this is very common.
7. Do not set any valve spring less than 0.110” (2.794mm) from coil bound, even for race use.

If the engine is dismantled for repair or maintenance, it is important that the tappets are kept in the correct order.  Each tappet is paired with a camshaft lobe and swapping the tappets around can lead to a camshaft failure.

Research indicates that most camshafts that wear out start to fail during the first few moments of operation.  Many camshafts are irreparably damaged before the engine is started, because the basic rules of camshaft running-in have not been followed.

The cause of premature camshaft and tappet failure is metal to metal contact between the tappet and camshaft lobe.  Should this contact occur due to lack of proper lubrication or excessively high pressure due to valve train interference shearing oil film, galling will take place.  When galling takes place, metal is transferred from the camshaft to the tappet or from the tappet to the camshaft in a process similar to welding.  Small areas (microscopic high spots present on all machined parts) become overheated due to friction and pressure and bond together, tearing sections loose from the tappet or the camshaft lobe.  These pieces of metal remain welded to the face of the tappet or the camshaft lobe and create further local overheating during the following revolutions of the camshaft and lead to ultimate failure of the affected camshaft and tappet.

There are a number of things that can lead to the ultimate camshaft failure:-

1. Poor lubrication during the first rotation of the camshaft with full spring pressure applied.
2. Interference in the valve train due to improper installation and failure to check for interference spring locking (coil bound spring) and collar to valve guide or piston valve contact are the main problems.
3. Fitting of used tappets on a new camshaft.  No matter how good tappets look, new tappets must be used with new camshafts.  New camshafts must also be fitted when fitting new tappets.
4. Petrol or other contaminant in oil that destroys film strength (or abrasive particles in oil that can cause wear).
5. Excessively long kicking before starting.  Oil will not reach the camshaft lobes until the engine is running.
6. Low engine speed during running in.  Camshaft lobes depend on oil thrown by the connecting rods for lubrication, besides the oil feed from the exhaust rockers.  Oil delivery will not be sufficient at tickover.

Make sure that the pressure release valve is set to open at the minimum oil pressure of 70 P.S.I.

CAMSHAFT WARRANTY

New tappets (camfollowers 067820) must be fitted before assembling the engine or the warranty will be void. 

Camshafts returned for inspection must be accompanied by tappets and valve springs. 

Tappets returned for inspection must be accompanied by camshaft and valve springs.

Removing and Fitting the Tappets 

The tappets are located in the lower part of the cylinder barrel retained by four 2BA Screws (two to each plate) passing through a separating plate for each tappet. 

To remove the tappet cut and remove the securing wire for the plate retaining screws.  The tappets are machined in pairs, THEY DO NOT INTERCHANGE.

It is most important when fitting new tappets, to apply camshaft lube (part number 067128) and ensure the chamfered edges are SIDE BY SIDE FACING THE FRONT OF THE ENGINE.  Inadvertent reversal will prevent correct lubrication of the camshaft and tappets.

Firmly tighten the plate retaining screws and secure with steel wire linking the two screws.

 Les Emery

Service Release 19/06/01

Copyright – Norvil Motorcycle Company 1982

Page last updated 27/11/02