13) Mind the gap

Gapping the valves and spark plugs.

September 20th 2019

The first job today was to remove the air cleaner from its paraffin bath. I gave it one last swirl around and left it somewhere to drip dry for a couple of days. The paraffin was definitely a lot darker than it was yesterday so hopefully a lot of dirt has been removed from the filter mesh.

Next I decided to tackle the valve clearances which is a good basis for any well running engine. Looking through the owner's club forum and also my workshop manual I found that all the valve gaps should be set to 12 thousandths of an inch. There was some debate as to whether setting the exhaust valves to 15 thousandths would help with cooling now that we use unleaded fuel but I think I'll stick to the book here.

Setting the gap on the first valve.

I removed the air filter bracket which on this engine shares the bolts with the rocker cover, then I removed the cover itself. This is the first time I've done valve clearances so I had to read up on the "rule of 9's" which is pretty simple once you get your head around it. I loosened all the spark plugs to relieve the compression off the engine to make it easy to turn by hand, then I methodically worked my way through each valve. As it turns out they weren't terribly far out. One was already perfect, a couple were too tight and the rest were close enough that they just needed a little tweak.

Once I'd set all the gaps, I refitted the rocker cover and air cleaner bracket. The gasket still looked pretty good so I re-used it.

Setting the spark plug gaps.

Finally I took each spark plug out in turn and set the gaps to 25 thousandths. Each one was already quite close but slightly too wide.

Another successful day in the garage, I'm looking forward to taking another test drive once my tyre valve stems arrive!