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Yamaha 3 Cylinder Stroker - Ted Broad / Barry Ditchburn

14177 Views 21 Replies 11 Participants Last post by  crazypj
The Broad Yamaha 3 cylinder Monocoque

I posted a few pictures of this bike some months ago under a different thread and over the following few days I was asked to post more photos, I was asked about the bikes spec and then to create a separate thread for the build.

So I thought on it and finally started writing but as always I got busy on other stuff. Nowt else for it I thought, PC on lap, late in the evening, half a bottle to the good I would tap away. Great plan, didn’t work, sleep usually getting in the way — Early spring through summer is always a busy time for me completing builds for race and road or prepping bikes for the riding season.

So this diatribe must be my 5th or 6th attempt at writing something, however this time I think I have a good chance of finishing it. Fingers crossed. What follows is everything I know about the bike, the thought process behind its creation, its development, those involved and its successes, followed by the bikes rebuild / recreation. I must stress that the story may not be complete as I said its everything I know from conversations with the Broad family and from digging out period publications. I hope you find it interesting.

Ted Broad Yamaha — A little history.

For those under 45years old and/or live on the west side of the Atlantic you may not of heard of Ted Broad but in the UK (and to a degree Europe) Ted Broad was a house hold name amongst motorcycling families, he was one of the most successful privateer sponsors of the 60’s, 70’s and 80's. Perhaps in a similar way to characters like Don Vesco or Don Tilley were in the States.

Ted’s tuning career started with British bikes in the early /mid 50’s reworking Norton and AMC singles but by the end of the decade had started tuning two strokes, reworking road going Yamaha’s into race bikes and developing bikes like the Yamaha TD1’s into race winners often beating the efforts of Yamaha’s works team. Over those early years Ted built and enviable reputation and was held in the highest regard by Yamaha so much so that the full works Yamaha team would pitch up Ted’s premises and use his workshops as their base for the TT and British GP’s rounds of the world championships in the 60’s.

It’s worth mentioning that Ted spent time in Japan working with Yamaha, developing crank and gearbox reliability on everything from TD to TR to TZ of all sizes and many of his mods were incorporated into the production bikes. Not limiting himself to Yamaha he also worked with Honda GB to improve the RS500 cranks, Honda (Jap) couldn’t work out why Keith Huewen’s engines kept going bang so Honda GB sent Huewen's cranks to Ted to sort. Ted also used RG500's and tuned the new Suzuki RG500 for his race efforts and ridden by Dave Potter.

As mentioned a key thing to remember about Ted is that he was a privateer sponsor. Although he was a Yamaha dealer and taking bikes from Mitsui, whose over the counter racer bikes were often not competitive, demanded that their production race bikes must be raced as delivered did caused a little friction between Ted and Mitsui (Yamaha). Eventually Ted stopped taking complete bikes for his own race team efforts preferring to building TZ’s from spares and to his preferred spec - Proving his point Broad Yamaha won the British superbike championship on home brewed TZ750’s in 1979, 80 and was leading the 81 championship until a tragic spill at Oulton Park, Broad Yamaha also won the BEMSEE champions too.

The list of riders Ted Broad helped along include Geoff Tanner, Reg Everett, Chas Mortimer, Paul Smart, Barry Ditchburn, Dave Potter, Jim Wells to name a few. He also prepared works RD56’s for Reg Everett, Phil Read and Bill Ivy, RD05 and 05A (v4’s) too. Ted also managed the European Transatlantic match race team for several years in the early 80’s his team winning several years.

It’s fair to say that Ted Broad along with the Frank Sheene, Geoff Monty and the Padgetts put Yamaha on the map in the UK and to a degree the rest of Europe. Sadly Ted died quite recently he was 91 years old.

The Monocoque Creation

In the late 1960’s a very talented engineer called Eduardo Giro designed a monocoque chassis to house the Ossa 250 engine (which he also designed), the bike was light and handled well when ridden by Santiago Herrero resulting in a 3rd standing in the 250cc world championship in 1969. This feat did not pass Ted Broad by.

Ted had considered that if he could build a bike that could carry enough fuel to complete a TT without stopping he could beat the "works" efforts. Pondering the possibilities of a monocoque chassis, both advantages and possible pit falls by 1971 Ted started work with fabricator / designers John Chisnell and Derek York, Teds bike was not to be a copy of the Ossa but rather his version, with a stronger headstock and load beam arrangement and a combined rear swingarm / rear engine mount. The only similarity was the material just about everything else was different including the engine, whereas the OSSA was a 250cc single 2 stroke, Ted fitted a 354cc Yamaha twin. Also the Ossa monocoque carried fuel in the usual place, forward of the rider, but Ted decided to use the full top line of the bike to tank fuel. What this meant was a fuel tank with a capacity of just over 7 gallons and therefore enough fuel for a 354cc bike to complete a TT without refuelling. Carrying this much fuel is problematic, a 7+ gallon fuel load is huge, so the chassis was fully baffled to prevent surging, the low seat height of 27” permitted the tank to stretched down to just above the swing mount lowering the fuel CofG.

Below is a photo taken end of 1971 of the steering column and load beam arrangement. Note the lower tube machined to take Yamaha rubber anti vibration engine mounts, same as those fitted to the front of the Yamaha engine.

Steering column / load beam arrangement (original photo).
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The load beam in position in the main chassis C beam (original photo).
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Yamaha TD2 based engine mounted in the chassis. Note the rear arm is a one off built to TR3 dimensions. Forks are Yamaha probably road YDS7.
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The chassis complete with just a few thing to sort before the season opener. Chassis builder John Chisnell coasting on the bike. This was the 1972 version of Ted Broad’s monocoque, the Mk1 if you like!
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Below the monocoque mk1 352cc engine, finished and photographed at Brands Hatch in 1972. Ted’s rider at that time was Barry Ditchburn, Barry later to become a works rider for Kawasaki alongside Mick Grant.
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The Monocoque Evolves

Whilst monocoque mk1 was being built Ted was working on his other secret weapon a 475cc 3 cylinder engine based on a YDS7 with an extra cylinder on the side, his experimental engine fitted into a standard YDS7 chassis. The engine used a combination 2x175cc top ends (from a 350) and a 1x125cc top end (from a 250) giving 475cc, a Yamaha based crankshaft made from 2x TR3 cranks with a firing order of 1, 3 , 2. Yamaha race cranks have 13 splines so a 120deg crank wasn’t possible (without spending big ££’s) so the crank was built out of phase.

Below is a page abstracted from a period magazine dated 1972 showing the bike and engine arrangement.
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Despite the experimental engine being mounted off centre in the standard YDS7 frame the 3 cylinder performed well winning races for Ditchburn and Broad Yamaha. The monocoque 352cc which proved to have impeccable track manners was doing exactly the same.

But why build a 3 cylinder 475cc? If you think about what was being raced in 1971/2 then there wasn’t a great deal of choice in the 500cc class, Suzuki T500 modified or oversize Yamaha TR3 both knocking out between 60-70 horses. The British singles like the Manx or G50 with 50hp were still racing but largely out powered by the Japanese strokers. So If a TR3 was making almost 60hp what could it make with and extra cylinder? 80hp? It was a no brainer for Ted.

By the end of 1972 Ted's 475cc triple was making almost 80hp, but with his eye on the UK superbike class (500cc to 750cc) he had also experimented with 521cc version using 3 x TR3 cylinders. This engine made 85hp and more than competitive against 75hp Tridents, 70hp Commando and Harley’s. The Suzuki TR750 triple was making more power but I was heavy and lousy handling, other rarities like the Crescent were unreliable. In fact most of the opposite were tipping the scales between 320 and 360lbs but Teds knew he could build his Yamaha based 85hp triple into a package weighing around 250lbs. That’s one hell of a power to weight advantage.

For 1973 it was decided rework the 3 cylinder engine with a new TR3 gearbox, later dry clutch and 3 x TR3 top ends fed by 3 x 34mm VM Mikuni carbs, sparks from a Pitsch Krober ignition. To cope with the extra horses it was decided to fit the reworked engine into the monocoque chassis fitting the engine centrally. The running gear remained largely unchanged initially but later the front end was swapped out for a Yamaha XS2 with 300m single disc. The bike tipped the scales at around 255lbs.

Below Ted Broad with his creation in 1973.
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…..and below the monocoque fitted with Yamaha XS2 front end.
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The 3 cylinder monocoque had its racing debut at Brands Hatch on the 20thApril 1973.
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This race meeting hosted a schedule of both national as well as the Transatlantic Trophy Match races and was part of a full international motorcycle racing weekend. The Trophy races moved to Mallory Park on the 22nd and Oulton Park on the 23rd.

Prior to the “debut” weekend the monocoque had been extensively tested proving to be both fast and competitive. Ted lobbied the European team management to allow his bike and rider into the European team but they refused. Why? I would speculate that the bike was unknown and a risk therefore. Ted entered his creation into 2 National races firstly the 750cc Superbike race and then the 1000cc race. Now Ted wasn’t the sort of man that believed in “happy accidents” and in both races all of the European team members were also entered. Below I have included the entry lists for both races, you may recognise some of the names!
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What happened next was a bit a fairy tale and must have embarrassed the British team. In the 750cc Superbike race Ditchburn was blistering and was mixing it with works riders on the 521cc Monocoque, chasing John Cooper to the line for a 2nd place. But in the 1000cc race Ditchburn won by a country mile beating the works guys again. Broad and Ditchburn nailed their point well a truly home, the monocoque proved itself in spectacular fashion. Many more race wins were to follow. Below is press photo of the Ditchburn on the monocoque in the 750cc race.
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Continued See next post.....


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What a great write up and history. I was 16 the day the monocoque debuted and really didn't have any interest in two strokes or road racing at the time (still messing around with very old BSA's and 'newer' Honda 50's)
Totally into trials and scramblers at the time (nothing much has really changed, I still can't afford racing)
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