Aye Andy,
More measurements!
Check both inner and outer valve springs on a surface plate with the narrow pitch [angle between the coils of the spring] resting on the surface plate, that they stand vertical. Maximum lean allowed from vertical in any direction = 1.7mm (0.067"). This applies to both inner and outer springs. If either spring of the pair for each valve leans greater than 1.7mm then the inner and outer springs need to be replaced as a pair.
Inner valve springs should be 40.1mm (1.58") in length, NO WEAR LIMIT ALLOWED!
Outer valve springs should be 43.8mm (1.72") in length, NO WEAR LIMIT ALLOWED!
WITH NO BENDS OR DISTORTION ALONG THEIR LENGTH.
When assembling springs in head, ENSURE NARROW PITCH OF SPRING COILS FACES THE HEAD.
You will see that this means the inner spring is wound counterclockwise toward the head and the outer spring is wound clockwise toward the head.
IF YOUR SPRINGS ARE TOUCHING AND WORN 'BRIGHT' FLATS ON THE INNER OR OUTER SURFACE OF THE WIRE, REPLACE THE PAIR.
ONLY USE OIL SEALS ON VALVE STEM FOR FINAL ASSEMBLY.
ALL MEASUREMENTS QUOTED ARE FOR STANDARD YAMAHA PARTS, IF NON STANDARD REFER TO MANUFACTURERS SPECIFICATIONS AND WEAR LIMITS.
I sincerely hope that this doesn't give grief, but greater reliability.
My regards, Bill.
