Cylinders Run Time & SPI Performance

If kept clean and well lubricated, a COX engine will work for many hours. I read that a COX factory experiment put 400 hours on an engine that still could be started up afterwards, with an electric starter though. https://web.archive.org/web/20170410030959/http://www.mccookfieldfac.com/helpful-info/cox-engines.pdf ...see 2nd page, top right.

I have a COX TD051 with tapered bore cylinder that I counted to have run near 300 hours and still runs very fast. Remember that castor varnish that builds up on the cylinder wall of a used engine can partly make up for the wear of the mating surfaces.

In my experience SPI can add 500-1500 rpm depending on the type of cylinder and other particular conditions.