Hi Peter,
B7HS does seem a little hard for road use. Too see the plug reach you can use a small torch and look down a plug hole – you can tell the difference in length between 1/2″ (short reach) and 3/4″ (long reach) easily with your eye.
Running long reach plugs in short reach heads gives two problems. The first is the electrode can touch the piston crown and close up the plug gap making starting a tad difficult. The second is the 1/4″ of thread from the plug that sticks down into the combustion chamber gets carbon coated and this makes the plugs very difficult to remove and strips the head thead in the process.
For NGK provided you have the 1/2″ deep threads in the head you would probably want B6HS or B5HS, with the respective Champion plugs being L82C and L86C. I note the post from Ted below about using L86 too.
You can find the full Scott fitment Champion range on my website if you are interested.
Cheers,
Rich
