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Bike Profile - Posted 19th September 2011

1980 Honda CB250RS OPAL Special
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Bob Peake took a perfectly good CB250RS and sawed it in half. Sob...

Honda built the air-cooled CB250RS singles from 1980 through to 1985 as lightweight sporting singles. Bob Peake wanted a suitable powerplant to propel a vintage-style machine, and he figured that a 250RS engine fit the bill perfectly. 'The purpose of the exercise' he explains, 'was to capture, as far as possible, the look and charm of a 1930s bike but incorporating the performance and reliability of a modern(ish) Honda.'

The five-speed, four-valve 250RS was known for its perky performance. Early examples came only with a kickstart, and it was one of these RS-A machines which Bob sacrificed to build his special. 'I purchased the donor bike, a runner with 11˝ months MoT remaining and with no little trepidation cut it in half with an angle grinder…'

Crowds thronged round the CB250RS when it was launched at the NEC show... 1980 Honda CB250RS

Some cruel, heartless people would say that's the best thing you could do with a 250RS but they know not of what they speak. The later electric start RS-Ds could be troublesome - often being easier to bump start than bother with the button which regularly malfunctioned - and all had a fragile top end if they ran light on lube. Tappet clatter could often be louder than the exhaust note.

However, if kept topped up with oil then the 248cc, 74mm by 57.8mm engine would keep going indefinitely, churning out 25bhp at first and over 30bhp for later models. The RS bikes were ludicrously light at less than 130kg and so proved extremely agile. Later RS-D machines benefitted from extra bhp but were also heavier, so most regular riders (these machines saw an awful lot of use on the despatch circuit) preferred the kickstart version. Both types were good for over 80mph, with the single disc front brake being well matched to their performance.

But I was never convinced by the square headlight. 1981 Honda CB250RSA

Wikipedia will tell you that fuel economy of 70mpg was possible - possible, yes, but not common. The twin pipes produced a very satisfying rort under acceleration and the RS always seemed happiest when being thrashed… so that's how most of them spent their days. The follow-on DOHC CBX250RS was nothing like as engaging or entertaining to ride, and was only produced for around 18 months. Honda attempted to replicate the appeal of the 250RS as a 500, and so created the XBR, but the bigger bike simply didn't have the mischievous nature of the original RS.

So to have found an intact 1980 RS-A with a full MoT and then take it apart with an angle grinder seems somewhat heartless, but Bob Peake had his goal firmly in mind. First, he needed to get rid of that pesky twin shock suspension.

Be careful what you wish for... Honda CB250RS Opal Special

'The rigid rear end was relatively easy, being built from 21mm o.d. x 16mm i.d high tensile steel tube. Using the same specification tube I built the girder forks - a much more complicated enterprise requiring eight "oilite" phosphor bronze bushes, spindles, grease nipples, friction discs, dog-bone linkages, main spring, star washer etc.'

'A much more complicated enterprise'... Honda CB250RS Opal Special - Front End
Honda 250s on Right Now......

The engine didn't need any modification, but Bob wanted something more suitable for a vintafake than a disc brake. 'The engine is standard, as is the exhaust system and rear wheel. The front wheel retains the original RS alloy rim but with a Honda CG125 Brazil 6-inch drum brake which I laced in after discarding the original disc and caliper.

'I have rewired the bike using a reproduction headlamp complete with period ammeter and switch. The toolbox is the famous "50p" item from a boot sale. All work has been carried out "in house" with the exception of the re-chroming (S.M.B. Launceston) and the stainless-steel downpipes (Alldens of Market Rasen).'

Visually, it almost works... Honda CB250RS Opal Special

So there you have it: one man's idea of a vintage motorcycle powered by a modern engine. Bob has christened it the OPAL; 'the name is derived from the initials of my grandchildren - Olivia, Poppy, Alfred and Louis.'

Well then: wotllitdomister? Bob reckons this is best summed up by one of his friends who took it for a spin. 'It's like a C11 with attitude!'

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With thanks to Ian Wright and Pete Mason for their technical advice, and to Tim, Phill and Richard of the Cornwall Classic Motorcycle Club for their help and encouragement.

The Cornwall Classic Motorcycle Club meet on the third Wednesday of every month at the Royal British Legion, Tideford (on the A38 between Saltash and Trerulefoot roundabout), starting at 7.30pm. All motorcycle enthusiasts are welcome to come along for a chat.

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