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Bike Review - Posted 15th April 2013
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Douglas 90 Plus and 80 Plus

The Dragonfly has become the most easily-recognised Douglas motorcycle. But, for Rowena Hoseason, the 90 Plus was the company's most remarkable achievement...

As regular RC readers will know, I have a soft spot for the deliciously eccentric Douglas twins of the post-war period. I've owned a couple (my Dragonfly is a permanent favourite) and thoroughly admire the engineering idiosyncracity and outright determination of this Bristol-based business. Dwarfed by the mass manufacturers of the Midlands - who built more motorcycles in a day than Douglas did in a week - Douglas Motors Ltd of Kingswood nonetheless created one of the most remarkable machines of the 1950s.

Style says Alabama, patched road says A14... Douglas 90 Plus sold by Bonhams for 6,200

At that time, the Douglas range consisted of one basic model in varying states of development and tune. The T35 engine evolved from a wartime generator motor, and was a unit-construction, four-speed, near-square 348cc twin - 60.8mm by 60mm; dimensions which contribute to the revvy (OK, sometimes 'thrashy' would be a fair comment) nature of these beasts. 20bhp was a creditable output from a 350 in 1945 - but the Douglas was all the more remarkable for its advanced suspension.

'Basically the best power unit.' No basically about it... Some advantages are:- vibrationless running; easier starting; longer life.
Douglas Stuff on

The front end featured leading link Radiadraulic forks which combined a laudably low unsprung weight with six inches of wheel travel and a sophisticated system of damping for a commendably comfortable ride. The rear suspension was even more remarkable given that most bike builders started their post-war ranges with rigid rear end, or plungers at best. Douglas motorcycles boasted a form of swinging arm suspension which incorporated torsion bars with rubber mountings. The result, claimed the company, was 'road-holding and steering far and away in advance of the majority of comparable machines. At all speeds, the road-holding is first rate.'

The Douglas twin was certainly sturdy and steadfast, but it wasn't exactly light at 380lb. The initial model suffered some teething troubles and it wasn't until the Mark 3 came along in 1948 that the Douglas hit its stride. This sports model featured an improved cylinder head design, revisions to the frame, upswept exhausts and so forth - the result being around 22bhp and a top speed of 78mph. That made it the fastest production 350 of its time.

But the best was yet to come.

Eddie Withers raced a tuned and tweaked Mark 3 during 1949, and from a series of promising results emerged the legendary 90 Plus for 1950. Stunning to look at, the 90 Plus delivered in performance terms, too. Each motor was carefully assembled and dyno'd to produce a minimum of 25bhp at 6500rpm (told you it was revvy), which translated to a genuine top speed of close to 100mph. During practice for the 1950 Junior TT, a 90 Plus was timed at 94mph. If one of the special engines didn't reach the 25bhp benchmark, then it was allocated to an 80 Plus which also benefitted from the running gear upgrades of its faster sibling.

I prefer the maroon to the gold.. Douglas 80 Plus

When you first see a 90 or 80 Plus, two things tend to wallop you between the eyes. The first is the colour scheme; gold or maroon, gob-smackingly gorgeous. The second is the immense front brake which probably would have stopped a 750 in its tracks at the time. But there are many other differences in fine details between the standard models and the Plus machines - so swapping components between them is a tricky business.

The monster nine-inch brake, for instance, is secured by modified mountings and is matched to a 21-inch front wheel instead of the normal 19-inch item. So while you can graft this brake onto a Mark model, it's not easy to achieve an ideal outcome. Worth the trouble, though; the big brake benefits from cast-in light alloy cooling fins and is secured via a ribbed, light-alloy backplate with the torque reaction being passed through independent linkage, thus keeping the front end of the bike level during extreme braking.

Note parallel acrrangement of torque arm and suspension linkage... Front brake and suspension detail

Plus models also have two-way damping at the front end, and distinctive headlamp mounting lugs - as the lights might be removed for competition occasions - rather than the permanent triangular headlamp brackets which you find on the standard, roadgoing machines. Then there's all the engine upgrades; the cylinder fins on Plus motors are tilted at an angle rather than being 'straight' (which in the case of horizontally-opposed twins like these is vertical). On standard 350s the exhaust pipes are simply push-fit items, on the Plus models they are fixed in placed with a threaded nut.

Alloy cylinders were fitted to some Plus machines - but not all, because this caused some problems with the steel through-studs which fix the heads to the crankcase, as the steel and alloy expand at different rates when the engine warms up. The Plus 90 has a special air intake for its clutch - but the 80 does not. Both are fitted with shorter cylinders than the Mark machines and have upgraded crank and gearbox bearing. The clutch is lighter and stronger than on the Mark models. The rear suspension is likewise beefed up on the Plus bikes, and even the rear sub-frame is subtly different to standard.

Shame about the jubilee clips... Douglas 80 Plus engine detail

Plus models might also feature rev counter, TT carbs, alloy rims, hot cams, racing mags, long-range and/or alloy petrol tanks, gearboxes with ratios suitable for all sorts of competition riding, and so on. You could soft-tune an 80 Plus to the point that it became a very well-equipped Mark 5 with pretty paint, or specify an outright rampant road-racer of a 90 Plus.

Around 500 of these machines were built between 1950 and 1953; something like 279 Plus 80s and 220 Plus 90s. These days they are far more rare and seldom come to the open market. A 90 Plus in kit form (mostly there but some bits missing) sold within days of being advertised in February 2013. A nicely-trimmed 80 Plus was offered for sale in NZ in the summer of 2012 and was repatriated to the UK for around (we understand) 4000 plus shipping and duty. A 90 plus was sold by Bonhams at auction in 2010 for 6210. This machine was fully restored and fitted with road-race cams; it came with the sprint gearbox as an extra, and was ready to ride with MoT and tax disc.

... Douglas 90 Plus sold by Bonhams for 6,900

A year later, another 90 Plus was sold by Bonhams. It had been off the road for at least a decade and came with considerably less provenance than the other machine - but sold for more, at 6900. At the time of writing, April 2013, we suspect that you could easily pay 8000 for a 90 Plus and would be very surprised if you find an 80 Plus for under 5000. The gorgeous, gold-and-chrome 90 Plus will probably be one of those motorcycles which continues to appreciate in value - how long before one sells at over 10k?

The 90 Plus was easily the fastest-ever Douglas motorcycle. It might have been the fastest 350 of its time, had that pesky Gold Star not been on the scene. Not bad for a tiny company which, at the time, was in receivership and had less than a decade of life left in it.

Words: Rowena Hoseason Photos: / RC RChive


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