Model 30M/40M Manx 4 Screw Main Bearing Securing Plate - Each

Product no.: 0286 A11M/34

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4 screw mainshaft bearing securing plate, to fit all Model 30M and Model 40M  (i.e. pre-Featherbed Manx type) magnesium engines. This pressed steel plate was used to retain the main bearings and ensure they did not 'walk' under heavy use. The plate was secured by 4 screws (sold seperately - see item 0024), which were soldered to the plate after tightening, to ensure they do not come lose. This plate is copied from an original item.

Price is Each

Note, if you are not sure what type of SOHC engine yours is - normally the only engine to use the four hole type main bearing covers were the competition magnesium crankcase engine bikes - originally referred to as 30M or 40m, or Manx Grand Prix Specification or later just Manx Norton.   These should fit all pre-Featherbed type magnesium crankcases (and might also fit some Featherbed type - email for dimensions if you need to check).  There was also a very early aluminium type racing engine crankcase (approx 1932-35, but without any web on the drive side in the shape of the Oilbath) - I believe they normally used the 3 screw fixing plate - but if are fortunate enough to own one of those engines and are unsure, email us for more information (

Hints for Securing The Screws On These Plates:

Original SOHC engines used slotted, unplated screws (which we supply - Item 0023 and 0024), so they could be soldered in place to stop them unscrewing when the engine was running.  It is important to ensure you use unplated screws, as the solder will not adhere to plated screws.   Once bearings are fitted, the plates can then be held in place and the screws tightened up with a flat bladed screwdriver.  Then, originally, these screws were soldered over - ensuring the solder flows easily  over the head and surrounding plate (without too much spillage).  To do this requires that both the corners of the plate and the heads of the screws are absolutely clean and free from oil.  I also tend to use a rotary  wire brush on both to remove any surface corrosion, just before soldering.  Originally I believe plumbers solder would have been used (not electrical solder), but a good quality solder and flux is required to get a good finish.  It is then a case of simplly getting enough heat onto the area surrounding the screw hole of the bearing retainer plate and the head of the screw, until the solder flows freely of its own accord - which can sometimes be quite difficult. 

I will not advise anyone how to do this - that is for each owner to decide for themselves, but many soldering irons cannot convey enough heat to get the solder flowing, so a number of people use small gas blowlamps, with well localised flames - but great care should be taken if doing it this method to avoid rags or anything close igniting.

A picture is also attached of an original engine with International type bearing retainer plate fitted, and screws soldered over

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