heavier valve springs on r6 yamaha

[brettk]

My son's racing an r6 Yamaha, standard motor, and I'm not sure whether I should be looking at getting heavier valve springs as I've heard standard they can allow a loss of contact with the cam, not full on valve float but not the best for the valves. I was wondering whether new standard springs and possibly shimming them would be a viable alternative to getting YEC kit parts which are designed to work in conjunction with their supersport cams .
How much can they be shimmed [.020/.040?] before any potential problems arise, or is the main thing to make sure there's at least .060" before coil bind?

[HJG]

You don't want 'heavier' springs. Heavy valvetrain components increase the chances of valve float. To reduce the tendency for valve float you would want stiffer springs. Stiffer springs are sometimes heavier but this is usually outweighed (no pun intended) by the increased stiffness. Alternatively titanium springs can work well due to their low mass, but should still retain adequate stiffness (remember titanium is not as stiff as steel).

Also, note that valvetrain friction increases with valve spring stiffness

[George111]

Has he experienced a problem which might be caused by the springs ? I had a ZX6r which had a rev limit of 16k and would spin to that limit regularly and I did 22,000 miles on it in a couple of years including track days. They are very well designed engines and very durable, I wouldn't change something that well designed and so critical unless necessary.