Annual maintenance

[John Vardanian]

Perfet! That is exactly what I was asking about. Thanks Dyke.

john

[Colin Angell]

You are spot on with the tolerances for end float or axial clearance of the rocker arms. This is a high wear area and often neglected, so it is not uncommon to see 0.15mm wear limit exceeded. Also the shim washers seem to be unobtainable! I make my own, by turning from bronze bar, Colphos 90, which seems to be a reasonable choice of material. From memory I have made them 1.05mm thick, which puts everything back within "as new" tolerance.

The bushes in the cam roller followers also wear quite rapidly and Ferrai UK are no longer stocking them. They will sell you a new roller with a bush in it, but that is at least four times the price and the rollers have a long life and will outlast several changes of bush. It is not difficult to push out the old bush and press in a new one, but you then have to bore or ream the bush to fit the pivot pins and of course the hole in the middle must be exactly concentric with the outside of the roller. I have made a simple jig, like a cup chuck, to achieve this, but have now run out of spare bushes. I am considering Colsibro as a suitable material for the bushes and would welcome comments and advice on this.

Of course all this takes hours, but what else is a winter service for?

[John Vardanian]

Hi Colin, thanks. The problem is the older generation motors do not have a spacer on the pivot shaft (No. 29 in the above diagram). If you look at blow-up of the cylinder head in the spare parts catalog of the older motor (the reprint of the very expensive “catalogo parti di ricambio”) you will not see the (No. 29) washers. When you say re-manufacturing bushes, are you talking about the ones marked as No. 27 in my previous post? Thanks.

john

[Colin Angell]

Hi John. I was meaning bush number "9", which the cam follower runs on. It just goes to show that a picture is worth etc.... I have just read your thread again and now understand your comment about the early engines. I guess that when things get too sloppy it wouldn't be difficult to carry out a modification to introduce the shim washers and I can't think of another way to reduce the tolerance. You would probably have to machine down the rocker body a little, but a shim washer say 0.75mm thick should be fine and give many years service. Colin.

[John Vardanian]

Yes, Colin, I understand now. No. 9 is also a weak point. The first time I took off the valve cover off my Type 168 I found one of these bushing almost completely gone. I doubt that the valve had opened for awhile, luckily it was an intake roller.

I guess what you are saying is that one can shave the No. 27 bushing of the earlier motor and fit the (No. 29) bronze shims that go with the later, outside plug motor.

john