John Smyth 4-1/2 hp Restoration – Part 4 of 5

Fitting and finishing the sleeve, and making a tank for the 1914 John Smyth.


| August/September 2016



smyth

Peter Rooke's 1914 John Smyth

Photo by Peter Rooke

This is the fourth in a five-part series on Peter Rooke's restoration of a 1914 John Smyth engine. Read Part 1, Part 2 and Part 3 for earlier stages of the restoration.

Fitting the Sleeve

Taking light cuts at the end of the boring process left a fairly smooth bore so it was not honed to ease the fitting of the sleeve, as some people suggest. The sleeve itself was measured at six different points around the diameter and it was a constant 4.753 inches. The cylinder had been bored to 4.751 inches so that there would be 0.002-inch interference fit, less interference than the 0.003 inch recommended, but ample for this engine. This fit would be plenty strong enough and it would not be necessary to use Loctite, as well.

Prior to fitting the sleeve, a steel disk used to check the bore diameter was skimmed so that it was an easy fit in the bore, with a step cut in it to fit inside the sleeve so it could be used as a press plate. A hole of 0.500 inch in diameter had been drilled through it so that it would take a threaded rod if it proved necessary to press the sleeve into place. One end of the sleeve was already chamfered by the manufacturer to make it easier to slide into position.

The sleeve was put in the freezer overnight with the expectation it would shrink by some 0.001 inch. With the steel disk in place it was found that it only took light tapping with a rawhide mallet to fit the sleeve, butting it tight against the shoulder that had been left at the crankshaft end.

Once the liner was fully in place the distance from the cylinder head end of the liner to the end of the cylinder was measured and a spacer ring trimmed on the lathe to 0.010 inch longer. The internal diameter of the tube used to make the spacer was slightly larger than the new bore diameter, but this was not of consequence as it was well away from the end of the piston travel. As this was a ring with a narrow cross-section that could be easily damaged, it was made to the cut diameter of 4.751 inches, with Loctite used to hold it place and keep it from rotating.

Honing

To accurately hone a bore an adjustable rigid hone is necessary rather than a spring-loaded glaze breaker. After fitting the sleeve the cylinder was bored out to 4.488 inches, with the final 0.002 inch to be removed with the hone. This smaller diameter allowed some tidying up of the piston.