Rocker Shaft thrush washer

Took off the rocker shaft retaining plate ((T.2239 - A24) to polish and plate it, and am wondering about the Rocker shaft thrust washer (18102 - A20). I don't see it. On a 69 'S' with production date of APR 69 on the ID plate. Am I missing something?

Dave
69 'S' project

Hi Dave,

Yes there should be a thrust washer between the rocker and the outside of the head (4 NM18102 specify in my '69-'70 and 850 parts books) Not a good idea to omit this as the rocker will wear on the alloy head casting.

The thrust washer you refer to is meant to go between the rocker outer face and the inside of the head that it bears against (ie the same outer position as the thackaray {spring} washer on the inner end of the shaft), it is only accessible if you completely remove the rocker shaft. These thrust washers can also be added to in order to achieve the correct central orientation of the rocker adjuster over the top of the valve stem. Simply removing the outer cover plate will not give access to or disturb this washer and in fact a washer here would likely prevent the inner plate with the two tangs from engaging with the rocker shaft slots and preventing the shafts from turning - which is the function of these tangs as the position of the slots are critical to allow oil feed to the rockers.

So when I take off the rocker shaft retaining plate (T.2239 - A24), the washer (T.2240 - A25), and the rocker shaft retaining plate (T.2238 - A23) and the paper washer (T.2083 -A22) there should be a copper ring washer (18102 - A20) that will press on the rocker spindle and compress the spring washer (18103 - A21)?? (From the 'Commandos spares list with supplements for 69 and 70' .) I guess this has been missing in my head, I'll have to get 4 of them before I put it back together but it seems to bear on the joint washer and locking plate (A22 and A23), not the AL head so it should only wear the locking plate and the washer? This washer is not mentioned in the Commando Workshop manual page 13 figure 3.

I am probably going to send this head to Leo Goff in TN and hopefully this will be taken care of anyhow.

Dave

Dave, when you take off the outer rocker spindle retaining plate (the one you are having chromed) under this is a paper gasket which covers the whole area of the plate, then there is a rocker spindle lock-plate (the one with the two tangs that fit into the slots in the shaft) and then another paper gasket with a hole in the middle. There are then no further parts accessible unless you start to dismantle rocker shafts from the head itself.
The rocker shaft does not require a thrust washer to preload it into the head, as it is anyway a tight fit and is best assemble using heat. It is the rocker side faces that require preload and shims and this is generally done when assembling the cylinder head.

Thanks Dave, but what is that item A20 (18102) and where do I find it or use it??

Dave

Dave, I'm looking at the Norton parts book exploded diagram and the numbers are different than those that you quote, however I'm sure we are looking at the same diagram and it is a bit ambiguous. In the one I have the 2 plates and 2 gaskets are to the left of the page and show them all close to each other, there is then a small gap and the washer in question and then another gap and the rocker. What it doesn't show clearly is which bits are inside the head casting and which bits are outside. For clarification the hole in the thrust washer you are concerned about is the same diameter as the outer diameter of the shaft ie. it can slip over it, so you can see that it would be ineffective as a thrust washer on the end of the shaft, it is however effective as a thrust washer on the sides of the rockers. The rocker shaft is immobile in the head, but the rocker rotates around it. The washer protects the rocker to head interface inside the head otherwise with hard iron rubbing into alloy you can imagine the rapid wear that would result.

The short answer to your problem is that you have no problem, there is no thrust washer missing from the outside of the shaft and you can go ahead and reassemble as you found it, when the plates return from chrome plating.

I think this is the thrust washer you are referring to. It is only .015" thick and can't really be seen unless you pry the rocker arm over toward the spring washer.

OK, great, that picture explains everything. The exploded view is a bit deceiving. I feel much better now.

Thanks everyone.

Dave