Materials Used in Yamahas

I have no gripe with the aluminum and steels used in: pistons, transmission gears, clutch parts, and the castings and side covers. Where I take issue is in the cam lobes, "holed" rockers, piston rings and pins, and most dowels. The cam drive gears/sprockets are fine. The rocker shafts are not. If it has teeth, it is usually very good quality. Gen I and Gen II idler gear #2 is plenty hard, but the engineering puts it in an impossible position. How many other manufacturers can you name who put in a magnet specifically to catch shaved off bits of the starter engagement gears?

I griped to a piston mfg about the quality of Yamaha rings and was told that he's seen it throughout the industry; and the difference between stock rings and really durable ones is about fifty cents per bike. I can sell flexible, durable replacements at slightly under the NOS prices. Almost none are still available through Yamaha.

There was no good reason not to put rolling element bearings at each end of the camshaft; except a cost of less than five dollars. The engineering would have been simpler. A cost of less than twenty dollars would have put in rockers with sintered pivot points and roller contact on the cam. Talk about durable. Alas, none of this came to pass.

In the '70s, I took apart many Honda and British twins. The Hondas leaked oil from the tops of the studs and from caps sealed with o-rings. It was minor. The Brits leaked from the base gaskets and the crankcase seams. It ranged from almost nothing to a deluge.

More to come . . .

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