Forty-seven months ago I put my son in a kart for the first time. He had a good season in the 50cc "kid kart" then a horrifying half year where I tried to make an old 80cc "junior sportsman" Birel work using a bicycle mechanic's set of skills. By then he'd expressed a desire to race bikes anyway so we went on two wheels and with the occasional indoor-rental exception we didn't look back.