Navigator cam followers / tappet bush wear

I believe it's the followers that wear more than the guides, I think the wear is caused by the angle that are at. The guides are cheap enough and easy enough to fit, but make sure the slots are away from the thrust face of the follower. The followers if they are still available are quite expensive and I don't think the engine will stay quiet for long, but you can live in hope! Good oil and low mileage will help! I've also fitted a filter.

Dan

Not sure if anyone has tried it, Andy might know, but, me , I just learned to love the rattle! It's not that bad, at least not on my jubilee at the moment, all I did was fit new guides.

I put the barrels in the oven and tapped them out, and did the same again to put the new ones in. I don't know why they used cast iron bushes instead of ph bronze, but it may be have been because of differential expansion, or its ability to deal with one sided pressure better ... in any event I think the followers wear more quickly? Having looked at all my old followers I don't think there is any scoring, which would indicate a lack of oil, they have just worn?

But what you suggest may work, and it would be easy enough to reverse if the need arises!

You could email Andy Sch.... Can't remember how to spell his name (sorry Andy if you are reading this!) asking him the same question ...... given that this is a known issue I'll be surprised if someone hasn't tried some thing similar?

keep us posted!

dan

They are not shouldered so can go in either way, I think I tapped them out and in from the bottom, As far as I recall I set the oven at 100 to 150C and put the new ones in the freezer before fitting, but they heat up quickly from conduction.

One thing i did learn was to clean clean out the hole with a circular wire brush in a drill before fitting to make sure they went in ok. I used a bronze drift.

Hope that helps!

Hi Dan (& others),

Sorry - took my eye off the ball and missed all this chat about cam followers - my least favourite subject on the Lightweights. I could bore you to death on the subject.

First, they are a legacy of the original design. The Jubilee was going to have a one-piece head & barrel - aero engine style. The powers that be changed their minds late in the day & thats why we have tiny pushrods. The original plan involved only a follower all the way up to the rocker. To make it rotate (to even out the wear), the cam lifted it off centre - that part of the design remains & now causes us grief, as the follower is still lifted off-centre in a very short guide & hence the shaft now wears gradually into a barrel shape. Run you two fingers and thumb along the stem - you will feel it. The picture attached does not show this effect very well - but you can see the step at the bottom of the stem where it has worn.

The cam followers are not just hardened on the stems - they are hard-chromed and ground to size. The foot is also hard chromed. The original method of making the foot was called end-upset. The end of the rod was heated to cherry red and stamped out in such a way that the foot was created. This made the material tough. Once hard chromed, it was ground back to be at right angles to the shaft.

The guides are made of cast iron as it has self-lubricating qualities. The oil drain slots in the guides need to installed across the bike.

As mentioned above, it tends to be the followers that wear, rather than the guides. The NOC have both guides & followers in stock (when I last looked).

These engines rattle as the cams are gear driven, there are two of them, and each one has two lobes opposite each other. So each cam opens a valve, it closes & repeat for the other side. Each cam is therefore suffering load reversals whilst being driven by an intermediate gear that is already suffering load reversals from the other cam.

Meriden Triumphs rattle for the same reason, whilst the big Norton Twin (& BSA twins) with one chain-driven camshaft fare much better, as there is always one cam lobe on load.

I'm writing this late at night - so I apologise for any errors.