Description of Part Required
a). Tappet Assembly (cam follower)
Model Number required for. All Lightweight models Jubilee, Navigator, Electra
Part Number 20871
Also used on if known. Only Norton Lightweights
Implication of lack of part Vehicle:- Off Road
Comments :- No new ones available
Routes you have tried to acquire the part and response received.
1. Commercial suppliers (e.g. Andover Norton, Norvil, RGM & NOC spares scheme) don’t seem to stock these items.
2. Tappets are similar but heavier than corresponding items from Ford ‘Kent’ engines.
Do you have a worn or damaged part available as a pattern? Yes
Based on price for similar parts, what would you expect to pay (give range)
£20 -30. (i.e. circa £100 for a set of 4.)
Comments: These components have a bad reputation for rapid wear. I wonder whether a
revised material specification for the bushes might be more appropriate.
20871 Tappet Assembly
- Log in to post comments
Dear Parts Commissioning…
Dear Parts Commissioning Team,
I have just emailed my Part Commissioning Request form off to the new spares team asking for the commissioning of a new production run of Tappets / Cam Followers part number 20871 for the Lightweight Twins.
My Navigator is off the road with the engine rebuild halted due to lack of these essential spares. The NOC Shop is out of stock and Norvil, RGM, etc don't even list these unobtainable, high wear rate parts.
I am very willing to put in a firm order for 4 new Tappets - the last NOC price was £40 + VAT. Although I am not made of money I would be prepared to pay up to £60 each to get my bike back on the road!
As an alternative to manufacture could the NOC consider identifying a reputable engineering company who could recondition worn Tappets? I believe the shafts and cam faces that wear are hard chromed and ground - manufacturing techniques widely used in Cam Follower manufacture.
Many thanks in anticipation.
Nick Clarke
- Log in to post comments
VW Beetle Type 1 cam…
VW Beetle Type 1 cam followers
19mm shaft 28mm head may work. They fit snuggly in the pushrod tunnels of the cast iron cylinder barrels that are 3/4" (19.05mm) diameter. Requires tappet bush (part no A40 20751) to be omitted and push rods to be made 20mm longer than originally fitted to lightweights. It is easier for push rods to be made that size than to manufacture cam followers. Millions of VW cam followers have been tried and tested, and are cheap (approx £10 each). Needs an engine to bench test the arrangement to give confidence to lightweight owners for their use.
GRAHAM
- Log in to post comments
Oil leaving the cylinder head
Hi Graham,
The general shape looks the right idea. Manufactured in Germany I'm surprised they used an OD of 3/4 ins.
How would the oil to the top half of the lightweight engine drain down if there were no slots in the side of the tappet bushes? I think that's the only way oil drains from the rocker and head area.
I love the idea of using a car engine part as it's bound to be a lot cheaper and quicker than manufacturing a 'special'.
Here's a picture of a set from an Avro Lycoming engine on Ebay at the moment. Sadly I don't have the dimensions but they look the same concept as Norton Lightweight.
Peter
- Log in to post comments
Oil leaving the cylinder…
Oil leaving the cylinder head
Hi Peter
I put this message on the commissioning site to suggest it is easer cheaper and safer to commission push rods than it is to get a small run of tappets made. (how can any quality control find out if the manufactured standard is ok.? Even the original tappets and guides wore out due to a lack of product development back in 1958 /1967!! ).
I will post a reply on the lightweight thread on new cam followers.
GRAHAM
- Log in to post comments
I have a friend just fitting…
I have a friend just fitting a new Lycoming engine in his Cessna, I’ll ask if he knows the follower dimensions but fear I may be too late!
Dan
- Log in to post comments
As an old Naval Aviator who…
As an old Naval Aviator who owned a much loved Jubilee as a teenager and now cherishes an even more loved Navigator I rather like the idea of using Lycoming cam followers! However, given the cost of aircraft parts they are almost certainly going to be more expensive than the bike!
I have just posted the suggestion that using the Ford cam followers and the NOC exploring the production of longer pushrods might be the better way forward. A tuned Kent cross flow revs to the same sort of limits as a lightweight and the engines have a good reputation for being robust and long living.....I have learnt over the years that the KISS principle is a pretty good approach in engineering!
Nick
- Log in to post comments
The tappet for Ford Kent engine is shorter than the Norton part, so perhaps a longer pushrod is required.
The diameter of the stem is the same on both Norton and Ford tappets.
The diameter of the flat head on the Ford part is considerably smaller than the Norton part.
So perhaps we should not be surprised if the Ford part is lighter.
Has anyone used the Ford Kent engine tappet with success? I wonder if the head is large enough to cover the wipe area of the cam.
Longer pushrods are not such a technical challenge.