21 replies to this topic

[jack be nimble]

After consulting with my guru uncle, (40 years as a mechanic, apprenticeship at repco, experienced in everything from whipper snippers to 16/71 blown 2stroke gm dump trucks, with a collection of villiers, indian, and other assorted stationary engines) he confirmed-

Yea, on a half worn engine you dont want to upset the layer of carbon that is on the side of the piston above the top ring. (Also the layer that is in the top ring groove behind the ring)
This layer of carbon makes giver a better gas seal and insulates the top ring from some of the pressures and heat of combustion.
The ring at the edge can be only 3-4mm wide. Just dont go to the edge.

This info can be found if you look in old factory service manuals where decarburising is part of a rebuild or service.

Edited by jack of all, 29 June 2014 - 12:03 PM.

[jack be nimble]

On this engine of the op, there is no signs of det on the pistons or the carbon would be the first bit hammered off.
When replacing those valves, check carefully for cracked valve seats as they may have caused the valves to burn.
Dont worry about the wash, its fine.

Edited by jack of all, 29 June 2014 - 11:58 AM.