B33 cams/cam followers

[Greenfield]

There is a very audible click when the exhaust valve on my 1950 B33 fully opens. With the plug out, and with the rocker cover and tappet adjuster cover removed, by turning the back wheel in top gear its difficult to tell where the source is. Sometimes I can see a definite twitch of the tappet accompanying the click as the pushrod goes over the top. I am suspecting that the problem is at the bottom end ie cam and or cam follower. I'm betting that this isn't going to be an easy fix. Any thoughts would be appreciated.
Cheers

[idie]

It might be that the valve is sticking in the guide or the tappet is sticking. I would go for the exhaust valve. Try putting some oil on the valve stem to seeing it stops.The same withe the tappet where it runs through the block.

[Greenfield]

My first thoughts were a sticking valve, particularly being the exhaust, but with loads of oil poured over it, nothing has changed. The cam follower is copiously oiled anyway. Its quite difficult to tell where the click originates but it does sound to be from the lower end. An interesting observation is that when the cam follower is rotated just before the gap is taken up, there's a tight spot; not good for getting the right tappet adjustment. So is there asymmetry in the head of the cam follower? It's looking like I'll be delving deeper.

[Greenfield]

Having slept on the problem, initially I was thinking that once the exhaust timing gear and cam were removed, the cam follower would slide down and out. I'm now thinking that the guide needs to be screwed upwards and out to allow follower removal. Therefore, can someone confirm that I can check the condition of the follower head in situ but to replace it, the guide must be removed.
It's always good to know what the job entails before venturing forth.

[chapmast]

To remove the cam follower then you will also need to remove the spigot as the head of the follower is too large to pass through the top of the crankcase, even with the guides removed. However I would not attempt to remove the spigot as it can only really be done by splitting the cases – the cases need to be warmed and the spigot tapped out from the opposite side. If you lose the interference fit on the spigot then you've wrecked the cases.

There is no asymmetry in the head of the cam follower; however it may be slightly bent - hopefully this isn't the case though.

A friend, Mark Quinney, had a similar problem on his Blue Star - unfortunately this turned out to be a bent timing side engine shaft. If this is the problem on yours then you should be able to observe it by turning the engine over with the outrigger removed – the gaps between the teeth on the cam and engine pinions will vary.

Mark now reports that he's hearing the clicks on his Sloper too.

[Greenfield]

With rain on and off I retreated to the warm dry garage for an hours fettling. Having removed the timing cover, plate and exhaust cam, I fully widened the exhaust tappet clearance which allowed the pushrod to fall clear. The cam follower could then be fully raised to allow close inspection of the surface with a dental mirror. The faces of both the cam and follower were in excellent condition. Having checked the bushes for wear, reassembled the the cam, follower and pushrod, and adjusted the tappet, everything if working but the click is still there as the cam goes over the top. Something to live with I guess. It's the same age as me and I have clicks now and again.

[Steve.S]

The red D.W Munro BSA book mentions tappet click on a couple of occasions.
Firstly, he suggests it can be caused by excessive cam endfloat, which should be no more than 0.002". Unfortunately, this can only be checked when the crankcases are split.
Secondly, he suggests it can be caused by incorrect meshing of the pinion teeth, for which the cure is either fitting new standard size pinions or new slightly oversize pinions, which he says are available. I've never heard of them, so perhaps they were only available to the Factory?
To diagnose the problem, if you look very closely at the teeth when turning the engine very slowly, just as the cam starts to close the valve, you may find wear on the teeth allow the cam to rock over as the play is taken up, causing the click......if you see what I mean?
Anyhow, if you insert a thin piece of shim, or cardboard or even rag into the offending teeth, and gently rock the engine back and forth, and the click disappears, you will have diagnosed the problem. I have yet to find a solution to it, but you might try a new half time pinion and cam pinion.
Hope this helps.

[Greenfield]

Mystery solved. A thin strip of cotton between the teeth stopped the click. Although the teeth look really good, a little bit of play although not noticeable, was the culprit. Whilst apart I'll fit a new timing plate bush as its a bit on the limit.
Thanks Steve, I'll sleep tonight.

[Steve.S]

Thanks for the feedback. Glad to help. Let us know if you ever manage to cure the click.