Valve Guides:
What started out as a simple exercise to check and adjust valve tappet clearances on my Navigator project has resulted in the removal of the cylinder heads and the revelation that the exhaust valve-guides are definitely worn out and the inlet valve-guides are not much better. A trawl through the Club Shop (again!) has left me rather bemused because there are apparently three different types of guides on offer: cast-iron, square-ended; cast-iron, chamfer-ended (as original equipment), and phosphor-bronze, square-ended. Any advice as to the why's and wherefore's of which of the alternatives is best would be very welcome. It also occurs to me that it might also be feasible to introduce a modern, rubber oil-seal between valve-stem and guide, to help limit consumption. Has anyone already tried that wheeze, I wonder?
Cylinder Head Gaskets:
The engine currently in the bike is of the post-1963 type without any spigot between the cylinder heads and the barrels. However, I happen to have a spare, early type engine, which of course does feature the 2mm high spigots . . . . and socketted heads of course. The pistons and corresponding bores of both set-ups are scarcely worn but, although the plain mating surfaces of the later heads and barrels are not warped, the head gasket shows signs of leakage. These observations lead me to another obvious, 'which is better' question. I wonder if the plain joint was adopted simply because it was easier and cheaper to manufacture than the earlier design of spigotted and socketed joint, despite the point that a gas seal between head and barrel is easier to achieve with the earlier arrangement? Should I delve further into the engine and swap over the barrels, pistons and heads whilst I'm about it?
Ian.
