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The diagram illustrates why not to use a roller profiled cam in a flat tappet engine. Normal cam profiles aren't shaped that way.
Stupid question time. Are there roller kits for 2 valve per cylinder Guzzi engines?
A little fact about adjusting tappets:This comes from the flathead/sidevalve generation. Flathead valves live in the block, not the head. They extended downward from the top of the block to either ride directly on the camshaft, or on a cam follower between the two. To adjust, you opened a plate in the side of the engine and stuck the feeler gauge between the valve stem and the cam follower. There wasn't any other linkage, so adjusting the tappets was a correct term then that made it into common (although technically incorrect) use over time.Looking at the roller tappet v flat hat, I don't see how they could modify a flat one to go roller. Roller tappets depend on a precise axial angle for the roller to work. In the pics you can see that the roller tappet holds that angle by virtue of its shape -- it's oval, not round. So it can't spin in it's bore and affect alignment. A flat tappet is designed to spin in its bore a little at every valve cycle so's not to wear unevenly. It seems to me that at some point of rotation, the roller in that design would be enough off-axis that it would drag instead of roll.But maybe they have a workaround by now . . .
There is lot of useful information posted above. It seems that roller tappets are superior to flat tappets.I have 2 questions:1. Have there been any problems with Guzzi's with flat tappets? I have a 2012 Norge which probably has flat tappets, because I understand MG switched to roller tappets during that production year?2. Since roller tappets have more moving parts, is there a greater chance of something failing in a roller tappet despite is superior design?