Based on the 350 cc Enfield Bullet.
by Mike Woof. Bike, July 1993
Putting diesel in a petrol tank is one of those nightmare situations that fill most riders with horror.
But with this Robin-powered Enfield, it's a sensation you'll get used to, although it may take some time because the 410cc Japanese-built Fuji mill will sip away at a gallon of diesel for 200 miles.
Dropping a diesel engine into a motorcycle is not a new idea but it's a concept that, so far, hasn't caught on. Let's face it, the average GSXFZCBZZR rider is hardly likely to be interested in a sluggish, 8.5bhp bike.
However, bland brakes, clumsy cornering and awful acceleration haven't stopped Harley 883s becomming popular with British fashion victims. And in the past year or so, the conventional petrol-engined, Indian-made Enfield has begun to sell in the UK to buyers wanting a combination of classic styling with 12V lighting systems.
Called the D-R400D, this diesel version of the 350 Enfield has some advantages over the petrol bike. Apart from the incredibly low fuel consumption, the leak-free engine only needs its one litre of sump-oil changed every 2500 miles and requires minimal maintenance.
Redbreast Industrial Equipment imports the engines, which are normally seen on things as diverse as lawnmowers, water pumps and dumpers. Previously, the company made a limited run of diesel-powered machines using old Matchless bits bought from autojumbles. But, made from original 50's parts, the bikes were not a commercial proposition.
The decision to use the Enfield was a logical one. It's one of the few bikes still made with a separate gearbox, ideal for the diesel engine transplant. Redbreast subcontracted Shol Engineering of Hythe, near Southampton, to build a limited run of complete bikes.
Using Enfield India running gear, bought from the Enfield importer, Bavanar Products, a chunk is cut out of the tubular steel frame and a big, steel plate bolted in to support the engine. Other modifications include running Enfield 500 gear ratios, re-machining the primary chain case to fit the diesel and using different oil seals accordingly.
The finish on some of the Indian-built Enfields can be pretty rough, so Shol Engineering strips down the Enfield to its basic components before powder-coating the fuel tank and frame.
A modified wiring harness is installed along with a bigger battery for the electric start (it has to work hard for a living, pushing that single piston up to a massive 21:1 compression ratio). Shol also set up the forks properly and fit better quality clutch and brake levers.
Next, the roughly-cast aluminium components are polished, all the shiny parts re-chromed and a stainless steel exhaust system fitted.
Starting is a doddle. Just pull in the decompression lever, push the electric start button and let the engine turn over a couple of times. Then release the decompression lever and let the thing chug into life. The kickstart is retained though, and a budget version is also offered without the electric boot. The kickstart itself has been converted from a handstart and is designed to eliminate the risk of kick-back. Gearing through the box is sufficient to allow relatively easy kicking and direct injection dispenses with the need for battery sapping glow-plugs.
Once it fires up, the engine thumps happily away, sounding for all the world like a sitde dumper. Saying that, the motor is quiet enough, running without smoking and with surprisingly little vibration for a single. To stop the engine, there's a kill lever sited, rather unhelpfully, just in front of the right footpeg. Clutch and throttle controls are very light but the gearchange is stiff and needs a hard prod, although the demonstrator bike was still being run-in. Finding the right ratio can be confusing, because like most old British boxes the lever in not only on the right but has a one up, three down set-up as well.
There's also a strange thing called a neutral finder. It's another relic from the original Royal Enfield days and consists of an extra lever, next to the gear lever which, when given a firm boot, will put you back into neutral from any position in the box. It's damn useful.
On the move, the bike is extremely sluggish and acceleration is, at best, gentle. Using plenty of revs and working the gearbox makes no difference to the take-off. It's easier to just shift into third once rolling and use the engine to do all the lugging. There's plenty of torque at low revs and the bike can actually move off the line in fourth gear without slipping the clutch too viciously. There's a drop in horsepower from the petrol-engined bike but Redbreast's bike can still slog its way up to about 70mph. This may sound feeble, but its pretty much the same as the 350 Bullet.
Being fairly light and low, steering and handling are surprisingly good. But the modest performance means things are unlikely to get out of hand anyway. Sitting upright on the wide seat, the ride is comfortable, mainly because the bike never really goes fast enough to upset the twin-shock suspension.
Forget precision braking too. The cable-operated twin leading shoe front drum brake is very grabby like the single leading shoe rear and both tyres howl readily. The stoppers are definitely not powerful, but, even though at 418lb the Enfield is slightly heavier than a CBR600, given the diesel's modest performance, they're adequate.
The crunch comes with the cost. At around L 4,500, it's no way near cheap. So who could possibly want something this expensive, when its nearest rival, the petrol Enfield 350, is half the price?
Paul Holdsworth of Redbreast admits that buyers would have to be pretty eccentric. But three bikes have already been ordered by buyers in the UK and Holland and enquiries have come in from as far afield as the United States.
One London-based courier company, looking to slash running costs, has made enquiries about buying a small fleet of diesel bikes. Fitted with 50s lookalike screens and panniers they'd certainly stand out from the crowd of CX500s and GT550s. How a diesel Enfield would fare at the traffic light grands prix is another story, and the shame of being run off the road by a Routemaster would drive most riders to suicide.
Remember though, this bike could be driven (slowly) from London to Edinburgh [approx. 500 miles] and still have almost half a tankful of fuel left. Show me a rider who'll sit on a bike at 50mph for that length of time and I'll show you an easy winner of the Japanese freak-game Endurance.
If diesels are considered environmentally friendlier than petrol engines, then this must surely be the biking equivalent of a [Citroen] 2CV covered with "Nuclear Power, No Thanks" stickers.
Fast it isn't, but it _is_ easy to master, stable and quite entertaining to ride. And with the prospect of bike insurance premiums being related to performance, as well as the ever rising price of fuel, this bike would cost almost nothing to run, albeit after a high initial purchase cost.
Just think, too, of the joy of never having to replace or gap a spark plug (heat generated by the monster compression is enough to ignite the fuel), being able to forget about electrical ignition timing and not worrying about cutting out when you plunge through flooded roads or fords (yep, goodbye to ignition coils, points, capacitors, distributors, HT leads and even trick, black boxes).
Sales are never likely to worry the Big Four, but then that was never the point. As Paul Holdsworth says: "We're trying to produce a bike for a guy whose standards are high." The D-R400D is likely to appeal to riders who want a very shiny, carefully rebuilt Enfield, for trundling along country lanes on a Sunday afternoon.
And, of course, on the rare occasion the tank needs topping up, there's always some fun to be had as a voice comes over the tannoy on the forecourt: "Oi, mate. Did you know you've just put five litres of diesel in your tank?"