Sunday, 7 May 2017

Ariel Single Timing Cover Fix

I noticed a while back that the magneto platform flexes more than it should, and this became more apparent when I set the ignition timing recently. It's down to the fact that the bolt retaining the magneto platform to the timing cover is missing, and the reason it is missing is that the boss it screws into is also missing...

Removing the magneto chain cover revealed another problem - a missing screw, replaced with a countersunk brass screw of dubious provenance, and within the cover, a burst screw boss:

So we need a man who can TIG weld aluminium and who has experience repairing old castings...

Here's the timing case, removed and cleaned:

This is the damage to the magneto platform bolt hole:

It went to Roo at  Roadkill Customs in Cromer to be fixed. He TIG welded the holes up:

I've used a stud, rather than the original screw. The original is tapped 5/16" CEI into the alloy, with a hex screw - heaven knows why it was specified like that.

This is a 5/16" CEI x 5/16" BSW stud. At 1 1/8" its a bit long, but can easily be shortened if need be, and the BSW thread will be stronger in the alloy.

I also replaced the rocker oil feed union while I had the timing case off. The thread was a bit mangled; a self grip wrench and a blowlamp were needed to get the old one out.

Draganfly have stock of these - I put this in and tightened it with the aid of a 1/16" twist drill:

I'm using some Threebond 1215 silicone gasket to replace the timing cover. It's grey, discrete and rated at 250°C. Ample for this application.

We need the additional paper washer over the oil pump pickup pipe:

New gasket, applied over a thin bead of Threebond:

And the timing case in place. The magneto pinion is held in place with a Velcro tape, awaiting arrival of the magneto. The breather has been annealed and straightened and the magneto platform is now retained to the new stud with a 5/16" CEI nut and a shakeproof washer.


  1. I have recently bought a VB. I have had to fix the previous owners[an engineer] rather poor assembly and use of parts with no thread, luckily I weld and machine. While looking for M8 bolt's to replace, I spotted a very gold looking screw holding the mag platform; I was just looking to see if I could see any pictures of similar Ariels, as there is a gap between the platform and the case? I looked and found a few pictures that looked like they have a gap?

  2. There shouldn't be a gap - the mag is held down with three 5/16" (IIRC) BSW screws, with hex heads.
    As a coincidence, my W/NG has one or two M8s where ther should be BSW or BSC - something to do with 75 years in Italy...