Fuller & Johnson Rejuvenation

Peter Rooke continues bringing this 1-1/2 HP Fuller & Johnson back to life with piston and cylinder head repairs – Part 2 of 4

| June/July 2014

piston head

Piston head showing the removed bolt and circular crack.

Photo by Peter Rooke

This is the second in a four part series on Peter Rooke’s restoration of a 1917 Fuller & Johnson 1-1/2 HP Model N. Read part 1, part 3 and part 4 for the full restoration process.

When I removed the piston and connecting rod they were covered in carbon, so I gave them a good soaking in kerosene before trying to remove the piston rings. Once the rings were free, I eased them off one by one by sliding three pieces of shim stock under them to lift them out of their grooves. As soon as I removed the piston rings, I cleaned up the grooves and it was immediately apparent there were steps in each groove, either from wear or a poor tidying job on the lathe.

One thing was clear when the piston was removed: Someone had fixed a bolt through the middle of the piston, with a nut and washer on the inside, but why? Even more of a problem was the crack in the head of the piston, which appeared to be slightly dished. Had a valve come free and been pushed back into the combustion chamber, jamming against the piston?

There appeared to be some wear on the sides of the piston, so before anything else was done I took a series of measurements of the cleaned piston.

First, I checked the piston diameter and it was soon clear that there had been uneven wear down one side of the piston: The top two lands were worn 0.006-inch more on one side. Wear was also excessive, being 0.032-inch less than bore diameter at one point. I also checked the piston ring grooves using a feeler gauge and a piece of square high-speed steel known to be accurate at 0.250 inches wide. The top ring groove was between 0.022-inch and 0.043-inch oversize and the other grooves were larger than 0.012-inch.

Taking into account the damage to the crown and the wear to both the piston and the bore, I decided a new oversize piston would be the ideal solution, but the chances of finding one over here in England is nonexistent.