This listing is for the camplate plunger and camplate plunger spring that was fitted into the brass plunger bush on all upright Norton gearbox Positive Stop Mechanisms. Original plungers often have a worn and flattened head, which can affect the effectiveness of gear changing. The same plunger was also fitted to the Norton Laydown Manx Norton gearbox. Price is for Plunger and Spring
These plungers are CNC manufactured then case hardened in EN32B to the same dimensions as the original item - and the plunger head has the same profile as an unworn original item (i.e. a rounded point). They come fitted with a spring, which again has been replicated by our specialist UK spring manufacturing company from an original Norton spring.
Background:
These plungers are fitted into the brass hex plunger holder, as shown in the accompanying photographs. It is normal to find that original plungers have had their head worn to some extent or another - and often, they are completely 'smeared' flat (as per the accompanyning comparison photo, that shows our plunger alongside an original worn example). When they get that worn, it is easy to understand that the 'positive stop' mechanism is likely to be less effective and no longer 'positive' in operation!.
Replacing with this plunger should restore some of that positive gearchange operation if your original plunger is worn.
These plungers have been CNC manufactured from EN19T (a very hard steel) to the original dimensions, and include the correct hole drilled 'off centre' to the plunger point, which was to stop the plunger 'hydraulic locking' when pushed into the plunger body. Likewise we have also had the spring manufactured to the same dimensions and gauge as an original spring. We also sell the spring seperately (Item 1011) if multiple springs are required, but this item includes both the plunger and spring. They should both be assembled with grease and ensure they slide back and forth smoothly in your original brass plunger holder.
It is worth noting that in writing the CNC programs and setup for this plunger - we looked at many original Norton gearbox plungers and found a selection of (different!) springs fitted to them. As this plunger and spring was manufactured for many years this is not surprising - and I am sure subsequent owners may have also fitted different springs. When making these, we used an original spring - but also ensured that the plunger and spring together resulted in the plunger sticking out of the body to what we believe was the definitive length (to ensure it gives enough purchase against the indent in the positive selector plate.
Note: As at time of this listing (May 2021), we are not intending to make the original brass plunger holder shown in the photos, as we are working on the theory that most people will just be replacing the plunger in their original gearbox. However, if your brass plunger body is badly worn, or is missing (i.e. you are building a gearbox from parts) - then email us on sales@racingvincent.co.uk and we may consider making a batch
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