Norton Upright and Laydown (Pre-AMC) Gearbox - Mainshaft Thrust Washer (all models)

Product no.: 0641 A2/328

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Norton Upright Gearbox and Pre-AMC (i.e. laydown) gearbox - bronze mainshaft Thrust Washer 

This bronze thrustwasher is splined and fits on the gearbox mainshaft, shouldering against the large mainshaft sleevegear.  It has small oilway holes and slots (that face towards the sleevegear) just as per the original.  This is a very important washer in a Norton gearbox as it acts against the mainshaft sleevegear whenever the clutch is pulled in.  Hence, a sloppy clutch lever with reduced leverage, added to a poor gearchange action, can often be traced back to this thrustwasher being badly worn - a very common fault!

We get a lot of people purchasing this thrust washer - no doubt because their original is badly worn.

These particular washers are made from 'Colisbro' bronze, one of most expensive and hardest of the bearing bronze's - as the best quality originals also were. 

They are 0.208" wide.  If you measure your current thrust washes and they are narrower by more than approximately 0.015" - 0.020" less, then it is probably worth replacing

An easy way to tell if your thrust washer may be worn? - look down at your clutch (which may require taking your outer primary chaincase off), pull your clutch in . . . if you see the clutch basket moving sideways (before the outer clutch pressure plate releases) by more than about 20 or 30 thou . . . chances are the thrust washer is getting worn, and some of your valuable clutch lever leverage is getting wasted!

Sorry these are not the cheapest, but cost of material and complexity of manufacture account for this - well worth it though if your original bearing worn!

Notes on Assembling Norton Gear Clusters: When assembling Norton gearbox's I normally check the gear clusters for alignment and any original shims (sometimes they are put in the wrong position.  Shims are normally only found on the end of shafts, between gear clusters and bearings . . . not between gears - which normally signifies a previous bodge or bad gear.  First of all I look to shim so that gears on mainshaft and layshaft are broadly in line, with as much of the gear teeth in mesh with corresponding gear on the other shaft.  Then I place ruler across gearbox casting gasket face and check for end float of gears on both shafts across this ruler.  I am not sure what the original clearance was - but I normally aim for between 0.003" - 0.005" endplay, and I would think anything more than 0.010" - 0.015" would be considered excessive.  

You also need to take the bearing/kickstarter boss position in relation to the end cover into play when doing this.  Any additoin/subtracting of the end cover bearing face to gasket face needs to be taken into account for the endfloat.  If when tightening the cover nuts, at the last moment the mainshaft tightens up or will not spin as easily as it did - then you have probably gone too far and have now got negative clearance - strip down and try again!

Once all assembled correctly, and gearbox sprocket tightened against sleevegear, you should just be able to feel perceptable end play on the mainshaft in relation to the sleevegear, but if it slopping around by a 1/16" or more - chances are the thrust washer worn or shimming wrong.


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