John Wyatt of Rising Sun Restorations

They’re still fairly easy to get hold of. Values range from around £1500 for a rough one, up to £5000 for a really nice example. On average you’d need to spend between £2750 and £3750. They’re usually either pretty rough or have been restored fairly well. The majority are in near standard trim, with a few fitted with big-bore kits, ace bars, exhausts, shocks and the like. There are more F1s available than F2s. Most who bought 400/4s bought the first ones and didn’t need another. People didn’t like the yellow F2 models, and they’d sit unsold in showrooms for a long while. If you look after them well, they’ll easily do 110,000 miles or more. The secret is maintenance. Change the engine oil without fail every 1500 miles; 10,000rpm kills oil. You’re better off using any decent 10/40w oil and doing the job at that interval, rather than running fancier stuff and leaving it in longer. Neglect oil changes and the motor will start to smoke. The cam-chain will last forever if you keep it tensioned. The manual tensioner sits at the front of the motor and can get covered in road muck and seize. Like all things, with enough time and patience it can be sorted. If you don’t keep it tensioned the chain will rattle and then flap about enough to start eating into the slipper blade’s pivot point. The front brake can stick on thanks to the pivot plate seizing. You’ve got to keep it cleaned and greased. David Silver Spares has a good stock of parts to keep your bike running, and though some genuine stuff isn’t easy to get hold of, there’s usually a pattern alternative. Care and attention are the keys to keeping a 400/4 running well. Look after it, and it’ll last forever.

Rising Sun Restorations are based in Tockwith, North Yorks: (01423) 358004