These bikers are safety-conscious, perhaps married, often leisure-only riders, and they have not been driven off the road by soaring insurance costs. Rates for youngsters can now be more than 10 times higher than for oldies.
The number of older riders on large-engined bikes has been rising - there are 25 per cent more bikes of over 500cc on the road than in 1990. Meanwhile, the last five years has seen a significant drop in the total number of bikes.
Younger riders, traditionally the main customers for smaller-engine bikes, seem to be opting for cars instead. One reason is that the price differential between cars and bikes has fallen. A new Yamaha DT125R commuter-style bike costs about pounds 2,700, the price of a reasonable second-hand car. But the high price of insurance has also put the brakes on. To insure a 17- year-old, living in a medium-risk area, on a Suzuki RG 125 Gamma bike might cost pounds 1,000 for only third-party, fire and theft.
Some three years ago, motorbike insurance premiums shot up. "This was down to a mistake in the industry,'' says Tony Snelling, technical editor of Motorcycle News. "Companies rated bikes by their engine size alone. They failed to notice the difference between more sporty bikes and the regular commuter models, or that one group was stolen and crashed far more than the other." Since then, insurers have made efforts to differentiate and to bring prices down for lower risks.
Young bikers have paid. Some companies refuse insurance altogether - Lombard General will not look at under-19s, or indeed any driver within 12 months of passing their test. Where insurance is offered, only third- party or third-party, fire and theft is viable - fully comprehensive is not worth the huge outlay.
A 17-year-old on a Suzuki RG 125 Gamma bike might pay 15 times as much as a 35-year-old with maximum no claims discount insuring third-party, fire and theft with Equity Red Star. Teenagers hardly ever use safety devices such as immobilisers or tracker devices - the bikes are considered too cheap to bother.
Older drivers get discounts for their age, and for restricted use. Niche classic bike insurers such as Footman James have particularly low prices. Norwich Union offers 20 per cent no-claims discount for two years' accident- free motoring. Overnight garaging earns a 5 per cent discount, 10 per cent can be knocked off for use of immobilisers (cost pounds 125-pounds 200).
Where the owner lives has a bearing on price. Living in a town involves more risk - more bikes are stolen and heavier traffic means accidents.
To keep premiums down, shop around. In a recent survey by Motorcycle News, some quotes were over five times as much as others for the same risk.
There are about 10 insurers and brokers that specialise in motorbike insurance, plus some Lloyd's syndicates, compared with 100 car insurers. Norwich Union has 60 per cent of the market, Devitts has 20 per cent.
Bennetts Insurance, NIG Skandia and Norwich Union give better quotes for young drivers. Cornhill, Equity Red Star (through Devitts), Eagle Star and Lombard are more suited to older, lower-risk bikers. Norwich Union and NIG Skandia discount for older bikers.