CitroJim wrote: ↑23 Feb 2023, 09:50
It's like Japanese cars never have any 13mm nuts or bolts...
Yes and no.
I have 5 old Japanese bikes. The 1980 Z650 and Z1000 have 13mm heads, the 1983 GPz1100 has 12mm, the 1995 Zephry 1100 has 12. I haven't got my 1986 TY250 here to check that one. So it would seem Kawasaki, at least, transitioned between 1980 and 1983. I would make an educated guess the year would be 1981 on the new models coming out and the last runs of the old models, like the Z650, would continue to use the old stock. The reason for this assumption is that my 1983 GPz1100 uses the Z1000 / Z1100 from 1981 to 1983 as a base manual and has a supplement manual for the extra things like monoshock rear suspension, anti-dive units on the front forks and the fuel injection system to name a few.
I worked for Toyota from 1991 in the factory at Burnaston and there wasn't a 13mm in the factory. Would be interesting to see if an older, pre 1980 Toyota had 13mm.
I can't guarantee this but I seem to recall, from my days there and knowing their philosophies, it was a cost saver. Miniscule but over the millions of nuts and bolts the saving would be huge.
Either that or they got a PSA bloke in the design department flipping a coin on some tarot cards
The 2 front lower bolts holding the hub on my Dispatch.......one end is 15mm, the other 16mm....on the same nut and bolt. The e torx studs holding the water pump on, on my C4 Coupé 2.0 Petrol 16V are E7!!! E7 doesn't come in a kit and the chap at the local motor factors questioned whether it even existed when I wanted to order one.