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FlatRacer BMW Mancha Branca project

FlatRacer BMW Mancha Branca

Our FlatRacer Mancha Branca BMW Cafe Racer started with a challenge from Clymer Manuals to produce a unique bodywork for their CCR project that was unfortunately shelved when Haynes took over.

This was the perfect opportunity for us to start our long ambitioned plan to develop a full fairing kit for the BMW R2v Series. We are great admirers of the original Cafe Racer look and British short circuit racers from the 60s but very seldom we see this kind of Cafe Racer transformation.

After nearly 5 years of slow development, it is here. The Flowliner full fairing offers superior aerodynamic advantages contributing for higher speeds, lower fuel consumption and enhanced rider's comfort..

To complement the look, we've developed a short tail kit (FlatRacer Daytona tail) so the bike's design would flow and the stance would be spot on.

As per our mission statement, the bike was to be modified without altering irreversibly its frame or other main ancillaries. Certainly a formidable task but we've allied our frame dictate with practicality by developing new stainless steel mudguards, fitted at the rear with our alloy L679 tail light.

Our Mancha Branca would serve as development mule for many other parts that we intend to incorporate in our catalogue of parts. These include our new FlatRacer Flowliner full fairing kit, FlatRacer/Tarozzi rear sets, FlatRacer 4.5" & 5.75" s/s mudguards, s/s battery tray kit, FlatRacer alloy triple clamp and many other parts for the Monolever and twin shock series.

As extra fun, we've decided to use parts from varied sources and models, confirming thus the interchangeability of components between different BMW R2v Airhead Series, from the 1969 /5 to the later 1995 Paralever, by using some ingenuity and great help from TwinFlat (www.twinflat.pt).

Our Mancha Branca features a 1990 BMW Monolever frame and a 1972 R60/5 engine bored to 800cc. The gearbox is post 81 (lighter flywheel), rear wheel from a GS mated to a 18" rim and the front wheel from a Paralever just to mention some of the most noticeable parts.

Below are our adventures and tribulations building the Mancha Branca.

FlatRacer Mancha Branca RH rear

Project progress

Due to our normal working hours and incredibly busy schedule, the FlatRacer Mancha Branca took several years to build and finish. Starting from Edgar's vision on how the full fairing should look to its painfully slow full development. We would like to thank the enormous help of Antonio Pereira dos Santos, Filipe de Sousa, Simao Branco and Fernando Rodrigues from TwinFlat (www.twinflat.pt) for their help building the running gear and Jorge Rocha for the outstanding paintwork.

Frame & Handling

We've started with a 1990 frame that we had laying about. Blasted and powder coated, it enabled us to put the bare bones on the bench and start. The centre stand had to be modified to accommodate the MegaCone silencers and /7 s/s manifolds (judicious use of oxy-acetylene). We've also shortened slightly the side stand as we've lowered the ride height; we haven't yet ground the rockers despite some spirited driving around the local twisties and roundabouts.

The combination of the superior Monolever frame with the shock mounted directly on the main frame, allied with the outstanding Hagon rear shock and progressive springs, a proper triple clamp, renewed bearings everywhere and sticky Avon AM26 Roadrunner tyres make for a very composed and smooth ride. In fact, we were astonished by the bike's eagerness to curve and the stability offered at all speeds, even at 200km/h.

The EBC full floating discs and pads and Hel braided brake lines help enormously the sense of safety.

Front end - Forks, wheel & bars

Although we've acquired a R100R front end at a later stage, we've decided for practicality purposes to keep the already refurbished Monolever forks but adopt the rare Paralever 18" front wire wheel, fully refurbished to our standards with s/s spokes and nipples, bearings etc.

Due to the under tank master cylinder from an early /7 Series (fairing constraints), we're forced to get inventive withe brake lines so a mix of /7, R65 and Monolever parts were used.

As the full fairing required the use of low bars, we've decided to adopt the Tarozzi race clip ons, one of our most popular products. However, as the Mono forks are 38.5mm and the clip ons are 38 or 39mm, we've resorted to use a thin piece of foil from a tin can, abrade it and use it as a spacer between the fork stanchions the clip ons clamps. Simple, effective and out of sight.

The top yoke is currently a machined lower yoke. We've designed a new alloy triple clamp that looks similar in shape to the lower yoke and will be available for sale shortly.

Engine & Gearbox

The engine was sourced and rebuilt for us by our friends Antonio Pereira dos Santos and Filipe De Sousa at TwinFlat (www.twinflat.pt). As we love the early /5 Series engine look with its clean and smooth lines and ribbed front cover, Antonio and Filipe used a R60/5 engine from 1972 and re-bored it to 800cc, using R80 pistons and cylinder heads. As a touch of performance enhancement, a 336 cam was sourced and fitted.

The gearbox is a later post 81 item, that accepts the lighter flywheel, making for snappier acceleration. Again, fully refurbished by Antonio & Filipe at TwinFlat although no major problems were encountered apart from a tired second gear which is quite a common problem (jumping) and fairly easy to resolve.

Although we are still doing the running in, we can feel the very snappy engine and eager throttle response. On a local drive to the beach, the engine felt very smooth and deceptively and effortlessly fast.

Carburetion

As the engine is fairly standard apart from the 336 cam, it was decided to keep the original Bing CV 32mm carburettors and air box although a free flowing K&N replacement air filter was fitted. Edgar prefers the original air box set up on standard tune engines as conical filters and air trumpets/bell mouths tend to deteriorate the venturi effect at lower engine speeds thus reducing engine tractability.

However, if your engine is seriously massaged for performance, trumpets or bell outs are almost a de rigueur conclusion for their greater capacity to fulfil the combustion chamber at higher revs.

After some tweaks, jet swapping and engine run in period, the engine is now running very sweetly and pulling strongly. It is a common fallacy to believe that smaller engines are not as fast as the R100 1000cc. A well-tuned R80 and R90 are quite quick bikes for their era and even the lighter R65 with its free revving nature will be an efficient point to point motorcycle.

Exhaust

A common problem afflicting the Monolever series is its centre expansion vase under the swing arm that makes it difficult to fit aftermarket free flowing exhaust silencers.

We countered this difficulty by adopting one of our s/s single balance piper exhaust manifold systems designed to fit the earlier /7 Series. In order to give us further clearance for the rear set foot pegs actuation, we've used 5mm nylon spacers between the frame and manifold clamps. It was then fairly easy to fit the FlatRacer MegaCone exhaust silencers by bending slightly their supplied chrome brackets.

New manifold/cylinder head ring clamps and big rose nuts (commonly found on the R69S and supposedly better at dissipating heat) were fitted without issue.

The noise is intoxicating and despite being loud, it is not annoyingly so, like the bark of some straight piped custom bikes.

Rear end - Drive train, shock & wheel

Very seldom you find good working original shocks on bikes that are +25 years plus. We've decided to shun the standard item and fit one of the outstanding Hagon N Mono shock. The N type features fully adjustable linked compression and rebound damping, and adjustable spring preload. Although we wanted a black spring, Hagon could only supply red, their trademark. Apparently there is a big war about corporate identity among shock manufacturers and their colour coded springs. Think of Ohlins and yellow, WP and white, Maxton and purple, Wilbers and blue.

Hagon came also to our rescue and were absolutely brilliant in adapting and lacing a flangeless (stronger) 3.00 x 18" alloy rim to our modified R100 GS rear hub (originally fitted with x-spoke 17" rim). Stainless steel spokes were used with nickel plated brass nipples. The front R100R rim was polished and re-laced with stainless steel spokes and nipples, including the small grub screws, preventing future corrosion.

We then fitted the very well-reviewed Avon AM26 tyres, 120/90 at the rear and 110/80 at the front. The sourced 37/11 bevel box was in excellent condition and required nothing more than a good clean and fresh oil.

Clocks & Electricals

Most of the electricals are bog standard BMW Monolever, however, we had to "plumb in" the L679 alloy tail light, the /5 speedometer/tachometer, voltmeter and clock. Although not overly complicated (there is a dedicated sub-loom for the 52mm gauges available from BMW for the RS/RT models), it does require time and patience. We've relocated the ignition switch to the modified /7 Series headlight shell, opening a hole to clear the speedo at its back and enlarging the main loom hole (larger on Mono models). As per our usual practice, we only use weatherproof connectors and properly insulated Lucar terminals (4.8 and 6.35mm) with clear silicon sleeves. No colourful pre-insulated terminals as these are a pet hate to us.

In order to splice the existing loom to the /5 speedo, we've cut the main harness to the clocks allowing for a generous length remaining on the original plug, this will allow us to fit a wiring connector and plug it at later date if the need arises to fit the original instrument cluster.

We've fitted a new alternator and diode board, again supplied by TwinFlat (www.twinflat.pt) and one of our high output voltage regulators. Battery is the truly superb Hawker Odyssey PC680.

Bodywork & Paintwork

The bodywork was certainly the most challenging part of this build. The reason why you do not see more Cafe Racers fitted with fairings, especially full ones is due to the difficulty in designing these to fit a specific frame, fabricate the fitting hardware and keep a balance between race looks and road usability.

Although an uphill struggle with many frustrating moments (the prototype fell twice on the floor!), it came through. We've used an old Doug Mitchenall (Avon) fairing design commonly seen on short circuit racers in the Sixties as an inspiration.

We initially made moulds of the lower RS/RT fairing panels and used the resulting stronger GRP parts (originals are a mix of plaster and GRP and fragile for this work) to build prototypes that would fit the upper section. Many kilos of fibreglass and polyester filler were used along with an incredibly strong GRP filler compound, Filite, which was also used on our moulds along with Kevlar. All was done manually using no more sophisticated equipment than an electronic level finder gauge and profile gauges.

We’ve played special attention to details such as symmetry (hard on an offset boxer engine), fairing bead edges, fitting hardware (similar set up to the original RS/RT fairings), acrylic headlight cover, and pre-fitted rivnuts among other niggles. As they say, the devil is in the detail.

The acrylic screen had to be done from a standard bubble, cut, trimmed and sanded to shape with infinite patience. Where the screen form did not follow exactly the fairing contours, we've used a heat gun gently to persuade into shape. Overall, it was over 6 hours of work. Our trademark acrylic headlight cover (incidentally is a 7” opening) was grafted in from one of our half fairings, providing a smooth a clean look.

Fully faired bikes can look heavy and out of proportion if positioned too high on the frame and/or used in conjunction with a long seat. As we did not want to cut the original BMW rear sub-frame or use an inferior aftermarket item (most do not align the seat with the tank bottom line and look to spindly), so we've decided to develop a short tail kit (FlatRacer Daytona), here upholstered in dark red leather and use our new 5.75" s/s rear mudguard to provide the optical illusion that the bike is short and muscular.

The Monolever side panels are certainly functional but not that attractive. We've decided to replace them with our own BMW /6 & /7 GRP replica side panels, which with minor mods fitted a treat. We are well aware that the current trend is to depose bikes of most of their practical components such as mudguards, side panels, indicators, battery trays, centre stands, etc. Notwithstanding, for us it is more challenging and rewarding to retain these elements in place and work around them and still obtain a good looking end result that remains a practical proposition for all weather riding. After all, it is just too easy to remove these elements and leave nothing in place.

The fuel tank is a standard Monolever TIC tank that came off a French Gendarmerie bike, which after knocking out some dents (welded pins and slide hammer) was good as new and treated to new tap and our own FlatRacer Monza deluxe alloy cap kit.

As we always recommend to our customers, we've assembled and dry built the bike prior to the final paintwork. This allowed us to envisage the best way to fit the parts and carry out minor tweaks without unnecessary and unsightly damages. Yes, time consuming and frustrating at the times but we can assure you that it is time well spent getting the minute details right.

Once we were happy with the bodywork and the way it would be fitted to the frame, it was only left to choose the colour and proceed with paintwork. Edgar did the preparation work and Jorge Rocha, our painter, gave it the final lick of 2K paint. This is Jorge's own formula based on the Old English White 250 code albeit warmer and used on his own car. Supplies were made by our long time favourite, Spies Hecker, who also provided their truly superb body filler for the prototypes.

The end result was well worth the effort and we are well pleased with the Mancha Branca looks, on it flows nicely together and has in our view the correct stance.

If you want to build a similar bike, please do contact us, we can supply all the parts featured in this project.