Agree with Ali, and GPR turn them round pretty quick.
Given that s/h radial m/cyls often go for as much on ebay as you can buy them new (if you get the ACU discount) I decided to invest in a brand new spare in case of mishaps at the track.....and so far haven't needed it!
Paul
15th year in DD #68 and getting slower by the year
1199, SS800 & 620SSie DD racer