Timing cover for rev counter

Generally, this mod is very straightforward and consists of just exchanging one cover for another. Over the years, there were about 6 variations of the Dominator cover, depending on badge type, rev counter gearbox mounting boss and pressure release valve.

The odd one out might possiblybe the early Commando Timing cover which looks like a Dominator type but may have slight locating peg differences.

Other problems that I have encountered are locating pegs set in the threaded holes by mistake, oil pump studs that were too long and a half-timing pinion spindle that was 5mm longer than standard. I have seen a few covers that have overlapped the crankcase face by a slight amount but never enough for the screw holes to not lines up.

Perhaps your cover is a factory reject. When Plumstead first started to build the 650 engine, things did not go to plan and loads of parts had to be junked as substandard.

Have you considered a Smith's Puca electronic job?

Some non rev-counter covers have been modified with a mounting boss welded onto them, complete with a suitable hole; not necessarily very nicely.

Would the 650SS cover complete with rev-counter boss be the same part number as your non rev-counter 88 item? I don't know, but wouldn't have thought so. You may have bought a modified one which comes under the category of not very well done...?

Did you buy it privately, or from a company? If the latter, and it is no good, I would ask for a refund. If the former, you may have found out why they sold it!

Back in the early 1960s, there were a number of small companies that offered 'go faster goodies' for Nortons such as modified timing covers and twin carb manifolds to fit standard 88 & 99 engines. Mr Dunstall being such. Perhaps you have a bad example of one of these.

Any chance of some photos to help check out the rogue item?

The 650SS cover is indeed different to the 88 cover.

We also made the same error when trying to fit a plain cover.

+1 for the Smiths electronic instruments - they are nice bits of kit!

I have attached a pic that lays theinside of an early twin timing cover (I assume this is like yours) and two later timing covers (as found on a late dommie, and an Atlas) side by side

You can see the outside shape is slightly different, and the location pegs are very slightly different too.

You can also see at some point, the oil pressure release valve was moved to the outside.

There were four or five slightly different variants of this cover during the fifties and sixties, so I am afraid it is not a simple case of getting a 650SS cover and fitting it to your bike.

There are also differences on the outside - you have a plain cover with no markings, a logo on a brass plate riveted on, a logo on an enamel emblem etc...

I believe that a Tacho was an option for the 88, and could either be specified as a factory option or a dealer fit option. In the case of the dealer fit option, they drilled the cover to fit the tacho drive themselves.

A factory timing cover with the cast-in boss for a tacho drive does exist, but I don't see them come up that often. You are more likely to find a hens tooth in a pile of rocking horse sh1t i'm afraid.

Hope this helps!