Timing gears

[Zetomagneto]

Thanks Richard.

I'm just trying to get the car going for now and am looking at rebuilding the engine over next winter. The dynamo housing was only off so I could renew a core plug, but I'm glad I spotted the broken gear as the next tooth along also has a crack in it.

I've sourced a good second hand Nippy pinion from  Ian Bancroft, who has leant me a selection of crankshaft gears to match up. He also modified the camshaft bush today to take up the endfloat - my set up measured .008" and a PO had installed a 40 thou shim (which I think probably counts as a washer) between the camshaft shoulder and the bush.

I can vouch for the truth of all the warnings about losing the rollers from the centre bearing. I thought I' d been quite clever putting a washing up bowl right under the sump, but three of the little buggers still escaped. I held the cam followers clear with small tie wraps and wish I'd popped one round the rollers when they first started to appear.

One interesting thing was that the crankcase had broken off a small lump at the bottom of the thread for the long bolt that holds the dynamo down. I thought that this had occurred due to the bolt having bottomed out, but Ian said this often happens due to oil and old gasket goo clogging the bottom of blind threads and so causing hydraulic lock when the bolt is run down. The broken lump was sitting behind the camshaft pinion and may have been the cause of the tooth breaking, or it may have been the excess camshaft end float. Backlash on the gears was .007".

If you are that far in I would use a modified standard cam, pigsty, Paul Bonewell, 
the Nippy cam wrecks Crankcase, i.e. cracks and stud issues on the camshaft side of the case.
Looking at your picture this does not look like steel, someone has fitted a cast gear at some time
in the past