I removed the steady plate from my 1951 â€œCâ€ Rapide, and found that the front cam gear (ET 157) had worn a groove on the internal surface of the plate. I appear to have the appropriate shims/thrust washers but am unsure. First of all, the cam gear and bush appear to be seated well and there is the appropriate-looking 1/2 inch thrust washer, but I donâ€™t know if it is of the correct thickness.
Paul Richardsonâ€™s book gives a description of the I.D of the washers, but no thickness is mentioned. Also, it specifies that both E95 and ET98/1 are both on the outside of the steady plate, whereas the parts manual illustration (MO13) makes it appear that both should be on the inside of the plate. Any clarification would be eagerly accepted.
Also, on a different note, the timing marks on the cam spindles appear different from the illustration in the Ownersâ€™ Manual - were there different ones used? In addition, my large idler gear has NO timing marks, and I could not see any timing marks on the crankshaft pinion.
Quick part response, short of time presently.
Never, repeat never, ever, ever, trust any timing marks anywhere anytime, cams can be pressed on pinions miles away from the proper place, breathers ditto, brethers spindles can be installed in the wrong place and can turn in the case, some idlers were made (a long time ago) with the marks in the wrong place anyway, did I tell not to ever trust any timing marks.
A degree wheel and DTI is your only friend for cam timing (both valves equally open at 4 Deg BTC is a good start place) having nipped the tappets for 5 thou pinch at the valves. Work backwards from there.
If the cam pinion is chewing the steady plate there is something drastically wrong, I'll be back shortly, if the all knowing sage David D does not appear after me.
Many thanks, TPP. I did not alter anything as the bike had been running well prior to removing the timing cover. I was having a heck of a time with oil-leaks, however, so I wanted to check the breather. I noticed that, not only were the timing marks missing on the (steel) idler, but barely visible on the breather cog. As I looked at it, I did wonder whether the spindle had been inserted into the cog in the appropriate position, but had no way of telling. All I can tell is that if I blow into the breather and rotate the crank, it does shut off and open up at roughly the appropriate times.
When it comes to re-do the valve timing I shall heed your warning and trust a degree wheel.
Meanwhile - the steady plate groove.....
If there is a groove on the inside of the steady plate it is probably due to the steady plate being bent slightly. This can occur if the spindles are not all at the same height. You may have a spindle or spindles pulling the plate down on one end and causing the groove from the ET157. I put a bit of effort into my timing chests to get the spindles all the same height. It is not complicated, but it takes some thought and a lot of shims from McMaster Carr.
I don't remember all the small details from memory, but I believe that there are two groupings of spindles: one group has the ET98/1 shim and the other uses the ET173 shim. Each spindle has one or the other shim between the steady plate and the spindle. If you note that the spindles all have 5/16" threaded ends to bolt down the steady plate, then any shims that have 5/16" holes are meant to sit on the shoulder of the spindle and are captured between the steady plate and the spindle. Because the two shims have different thicknesses, their respective spindles need to be set at different heights.
When I say that the spindle has to be at a different height, what I mean is that I use the timing case cover mating surface as the datum for the height. The spindles poke above the mating surface on the crankcase, so I use a 1" X 1/2" X 9" ground bar to span the timing chest cavity so I can put the bar 1" high and measure down to the spindle shoulder, or the spindle shoulder with the appropriate shims on the spindle. In the past, the ET98/1 shims were .025" thick. I ordered some recently and they were .030" thick. This is not the end of the world, but if you want all your heights to be the same you need to be consistent. This is why I have a selection of shims from McMaster. Anyway, the ET173 shim is .071" thick. These shims go on the large idler and any small idler. So, it is best to measure down to all the spindles after you have placed the "under the steady plate" shims onto the spindle shoulders. If you do this, all the heights should be the same, because the steady plate should be flat.
When I do a Timing chest I use all Maughan spindles and the large idler mount. It is the large idler mount that sets the datum for all the other spindles because you cannot lower the large idler mount. Thus, the large idler mount with the ET173 on the spindle will set the max height for all the other spindles with their respective washers sitting on top. There is no need to worry about what goes on top of the steady plate, because you are focusing solely what is underneath the steady plate.
This should give you the basic idea about approaching timing chest assembly. Most good Vincent mechanics will do this one way or another. Most Vincents run fine with bent steady plates and do so for a long time. The long term worry is particles of aluminum in the oil and the possibility that a low spindle has the tension of the steady plate trying to pull it up or vise versa. These are real problems, but not the most urgent.
Thank you so very much for that incredibly detailed account. I am very grateful. You confirmed my suspicion about the plate being bent because of uneven torquing due to uneven spindle heights. Your information gives me a wonderful starting point.