Custom Moto “Mental” Martin CBX1000 Turbocharger!

Honda CBX1000 wasn’t the first six-cylinder road bike – Benelli had already beaten Honda with its 750 Sei – but with its spine tingling yowl from the pair of upswept silencers it was an instant reminder of the Japanese giant’s sporting heritage from the early 1960s when its multi cylinder four-strokes ruled the racetracks.

Custom Moto “Mental” Martin CBX1000 Turbocharger!

With 24 valves and more than 100bhp on tap from the 1047cc engine the road testers of the time soon discovered that not only was the big Honda visually, technically and audibly stunning it also delivered in the performance stakes with a top speed approaching 140mph. Weighing it at 600lb (272kg) the Honda CBX1000 was no lightweight but by moving the alternator, ignition system and starter motor above the gearbox the six-cylinder engine was only two inches wider than the CB750 which allowed for a generous amount of ground clearance and using it as a stressed member of the tubular frame meant that there were no messy downtubes to spoil the visual effect of Honda’s new superbike.

When the first test bikes became available the period journos were soon waxing lyrically about the CBX1000’s many attributes with the American magazine Cycle likening it to a boxer’s “cosmic hay-maker that caught the state-of-the-art right in the ten-ring and put all the pretenders back where they belonged.” They also went on to say: “Its European texture is a breakthrough for the Japanese motorcycle industry. Its high speed handling and cornering clearance are remarkable, its drive-line character is unflawed and the linear responsiveness of every control system is unique in all of motorcycling.”

Almost every press test came up with plenty of praise for the big six but there’s an old truism that says ‘a great motorcycle will not always sell in great numbers’ and this could just have been dreamt up for the Honda CBX1000. In the all-important American market – traditionally dominated by cruisers and tourers – not even the introduction of a fairing, Pro-Link single shock suspension, uprated brakes, air-assisted brakes and a pair of panniers in 1981 could get them moving from the showrooms in sufficient numbers, and despite decent sales in both the UK and Europe the six was consigned to the history books at the end of 1983. In another period magazine article the tester joined in the praise by writing, “Quite simply there’s never been a bike like the CBX1000,” words which certainly left an impact on a young man from Wiltshire.

Custom Moto “Mental” Martin CBX1000 Turbocharger!
Paul and his amazing machine!

Four decades on from first lusting after his dream bike Paul Pursey now owns five of the fabulous sixes; one of which is no ordinary CBX1000. It features an 1170cc turbo charged engine mounted in one of the beautifully crafted frames made by the Frenchman George Martin and proved to be a real head turner when it was wheeled out at the Carole Nash Bristol Classic MotorCycle Show last February. The depths of winter is not the sort of weather to be taking a 200bhp monster out for a spin so when the warm weather came I visited Paul who told me a little about his biking background, his love for CBXs and the bike which he’s nicknamed ‘The Money Pit’.

“My first bike was a Honda 50 field bike and I then progressed to a TL 125 which I rode in schoolboy trials,” says Paul. “In the late 1970s the Honda CBX1000 was released but for a teenager this was like something on a pedestal and I had to content myself to a Yamaha FS1-E and later an RD 250 until at the age of 29 I got my first CBX – in red – which I’ve still got today. This one and the other four I’ve owned have been standard bikes but I’d always admired the frames made by the Frenchman George Martin – I think he made around 100 for the CBX – and when this one came up I decided it was too good an opportunity to miss.”

Custom Moto “Mental” Martin CBX1000 Turbocharger!
The motor dominates: Sony camera wasn’t a Honda option back in the day!

When the new generation of Japanese superbikes appeared in the early 1970s Martin was quick to see that the engine performance was vastly superior to that of the braking and handling, and in 1972 he started building his first race bred chassis. This was similar to the backbone design that Fritz Egli was making down in Switzerland; most of the first batch housed Honda’s SOHC CB750 engines and over the next 16 years some 5800 beautifully constructed frames would roll out of his factory at Les Sables-d’Olonne.

Paul says: “Prior to me buying it the bike had done some drag racing – I believe Pip Higham built the engine – and it was a bit scruffy but at the time my intention was to have some fun riding it and there was no thought about restoring or modifying it. All that changed when a friend offered me a top-of-the-range swingarm and suddenly the whole thing snowballed and before long it was a total strip down.”

“I decided to go the whole hog and fit it with a turbocharger – supplied by Mr Turbo and originally designed to go into snowmobiles and small tractors – so the whole engine was stripped and upgraded. This included a modified crank, special pistons and rods, a big valve head, an uprated oil pump, undercut gearbox and a hydraulic clutch conversion. I did all the work on the motor myself but in completing the whole rebuild I had to have 500 one-off engineering jobs done by the late Ralph Pullen – he did a fantastic job – and I reckon it probably cost me around £9000-£10,000 on the engine parts alone.”

“The frame had to be modified to accommodate the bigger swingarm and the turbo and to give some decent suspension at the front I used a pair of forks – complete with some wavy discs – from an R1 along with some custom-made top and bottom fork yolks. Also from an R1 was a JCM rear swingarm and hugger but I couldn’t use the standard rear suspension linkage so I made my own; initially making it out of cardboard and when I was happy it was going to work I then fabricated it out of metal.”

Custom Moto “Mental” Martin CBX1000 Turbocharger!
Quirky looks and amazing performance.

Paul is a stickler for detail and unlike most bikes where the wiring loom – this another homemade item – is held together by cable ties those on the Moto Martin are secured by discrete tabs welded onto the frame tubes and are invisible to the naked eye. The seat is from an MV Agusta which covers the gel battery – this is mounted on its side – while the front headlamp fairing – originally on a 50cc Gilera moped – along with the tank and footrests were painted by John Tooze at Born to be Wild in Gloucester, leaving just a pair of gleaming white Dymag wheels to finish the package.

Not only does the finished bike look fantastic but the turbocharged 1170cc engine – it’s been measured at 200bhp – also gives it plenty of go and on an old airfield it’s been timed at 165mph. Paul assures me that there was plenty more to come but with just that small bikini fairing to keep the wind at bay it was almost impossible to hang on; I’ll leave it to your imagination to conjure up a mental picture of the exhaust note from the exquisitely crafted six into one at that speed!

We didn’t have an airfield to test out the turbo’s top speed but it was obvious from just a brief ride along the lightly trafficked roads of West Wiltshire that this is an awesome beast. With its very limited steering lock it’s not the sort of bike to do feet up turns, but once on the move both the handling and the performance are mind-boggling.

Keeping to the speed limit it’s like a pussycat but give it a whiff of throttle and as the turbo kicks in it instantly turns into a tiger; and it’s all too easy to see why the creator has given it the name of ‘Moto Mental Martin’. With the huge rear tyre breaking traction in both third and fourth gear on a dry road it’s not the sort of bike you would want to ride in the wet; however unlike some specials which are just ‘trailer queens’ Paul’s CBX has seen plenty of action in the last 12 years.

Custom Moto “Mental” Martin CBX1000 Turbocharger!

Custom Moto “Mental” Martin CBX1000 Turbocharger!

Along with other enthusiastic members of the CBX Riders Club – Paul is the South West representative – the Moto Martin has been taken to several European rallies including France, Denmark, Switzerland and Holland where not surprisingly it has created a huge amount of interest and also won its builder many trophies. These are small reward for many hours spent in the workshop but he is quick to acknowledge all the help and support he’s received along the way in creating his dream machine.

“The CBX Riders is a great little club,” explains Paul. “Not only do they organise various rallies, pub meets and ride outs they are a great source of spares and technical knowledge; certainly rebuilding a six would be a nightmare if it wasn’t for the help you can get by just making a phone call to the right person. The bikes are inherently very reliable and most spares are still available – eBay America is a good source – but some things like genuine exhausts are now like rocking horse manure and a good one will set you back around £1000.”

Creating the ‘Moto Mental Martin’ has been a costly affair – reflected in the rear number plate which reads ‘The Money Pit’ – but there is no doubt that the smile on Paul’s face when the big six bursts into action makes it all worth it; it’s one fabulous machine!

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