Hi Guys...
The timing cover that came with my basket case project 650SS was in pretty rough condition, but has a tachometer drive gearbox attached. I'm fairly certain that the fixing is not correct, however. The two fixing holes in the cover have been tapped out 5/16" BSF (?). The tacho drive gearbox mounting holes are 1/4" diameter and it was attached to the cover with two 1/4" BSF screws, through the tapped holes, with nuts on the inside that had been "peened" over to stop them coming off.
I have acquired a much better timing cover which I hope to use. This has two un-tapped, 3/16" diameter plain holes for the tacho drive gearbox fixing. I'm assuming that this is correct and that the gearbox should be attached with two, 3/16" diameter screws and nuts on the inside of the timing cover. Or... should the timing cover be tapped for 1/4" diameter screws?
As always, any help of guidance would be much appreciated.
John
Timong cover differences
John,
There are two (that I know of) different timing covers for the angle of the rev counter drive. The Atlas and the Mercury have the mounting holes vertically aligned whilst the 650 SS have these holes at an angle. This is so that the drive cable is routed away from the different exhaust pipes.
The fixings are 3/16" cheese head screws on my Mercury. I'm pretty sure there are no nuts on the inside of the cover.
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Thanks
The holes in my timing cover are at an angle, as they should be for the 650SS. They are 3/16" diameter, as near as I can tell by using drills as pin gauges, but just a plain hole, not threaded. On the Andover Norton website, the mounting screw part number (23444) in the list in the previous posting is a 3/4" long 2BA screw which is a couple of thou larger than 3/16" but goes through the hole in the timing cover. The inside of the cover has been spotfaced where the holes come through. Presumably, that's for nuts to seat against?
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Dominator Service Notes Update
Checkout the DSN update as found on this very website. There is a really great article put together by Bruce Tinworth, about the various Norton Timing Covers as found on the 1948 to 1970 Dominator bikes.
The first Atlas 750 models used the angled rev counter mounting as found on the 650 and some earlier Dominators. This was changed around 1965 (at E/N 111379 for the vertical mounting boss which better suited the standard exhaust pipes.
The DSNs also mention the rev counter being held in place by 2BA x 9/16" screws. Often these were overtightened during rebuilds and needed either re-tapping a size up or replaced by through bolts with nuts.
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