What size are the 2 upper mounting bolts on a 1998 R1 engine? The one is neither M10 nor M10 fine pitch and the other is neither M12 nor 1/2" UNF.

If you mean the socket cap head bolts, the thread is m9 x 1.

They are as rare as rocking horse shit, so I got mine direct from yamaha for about £2.

The ones on my 2003 engine were all M10 fine, so they must be different on earlier engines

M9 doesn't sound right for a mounting bolt - all of mine ('99 R1) are either M10 fine or M12 fine.

For reference, I've just fitted two M10 x 1.25 mm pitch bolts to one side and one M12 x 1.25 mm pitch bolts to the other.
For the other mountings, I've passed M10 rod through the plain hole and used nylocs at either end.

Exactly as per Mr smart51
Bob C - early carb R1

I recently bought a longer M12 bolt for the mounting on the 'front' of the R1 engine (as positioned in a BEC) and it has 8.8 stamped on it. Should I ideally be going for something of a higher tensile strength?