Villiers 196 super sports

[Vreagh]

Hi, I'm trying to identify what this 196 engine might have been fitted to originally, at the moment it's fitted into my built like a bridge frame.  It looks like the standard super sport engine but has no decompressor and no provision for lighting coils or oil feed. Engine no is KZB 179 definitely a B and not an 8. Although it starts and runs well, I'm having trouble kicking it over compression and all the heads I've seen have a drilling between the exhaust ports. I'm thinking of drilling and fitting a Royal Enfield decompressor but don't want to ruin what might be a rare head. Any thoughts please?

[cardan]

That's interesting. I think we might need a photo.

Most Francis Barnetts used the 172cc Super Sport engine, which has prefix BZ. The hot Brooklands version has prefix Y.

KZ is the prefix for for a 196cc Brooklands engine, but I'm not familiar with KZB... Maybe it's some variant on the Brooklands/Super Sports.

The drilling in the cylinder between the exhaust ports is for an oil feed. The Brooklands head has a boss for a decompressor, but it is usually not fitted. Perhaps super-sporty riders/racers made do without a decompressor. If it's a huge problem, maybe you could use a thin aluminium gasket under the cylinder (not too thick or it will change the port timing) or a thicker head gasket to lower the compression a little.

Leon

[cardan]

The drilling in the cylinder between the exhaust ports is for an oil feed.

Or perhaps to get some pressure to drive the weird Villliers oiling system? That would make more sense.

[R]

Some clarity needed here
He is talking heads and you are talking cylinders 

Might be a slip of the pen.
But that photo would help ...