Tuesday, February 4, 2020

How he converted a Royal Enfield to diesel power

Royal Enfield motorcycle with diesel motor.
"It is a Royal Enfield with a diesel engine shoehorned into it."
A 2008 Royal Enfield Electra neatly converted to diesel power is for sale on eBay in New Jersey. It has electric start and kick start, a five-speed gearbox changed to shift on the right side, and a top speed of about 52 mph.

"This is a crude rough ride that will get attention and is a blast," the seller writes.

"If you ever dream about blasting into town on a tractor/rocket hybrid, this will fit that need. Am I the only one? We will find out with this auction."

Royal Enfield motorcycle with diesel motor.
Diesel cooling fan and shroud are distinctive.
The ad describes the largely stock Royal Enfield motorcycle and its rebuilt Lombardini 6LD360 air-cooled, single-cylinder diesel motor.

I wrote the seller to ask for more information about the challenges he faced in making it.

But first: why do it?

"About three years ago I really wanted to import a Royal Enfield Taurus diesel from India, but it was just dead end after dead end, so eventually just did it here and was able to get past all the issues/shortcomings of the Taurus," Anthony wrote me.

Royal Enfield motorcycle with diesel motor.
Diesel retained its own muffler and the stock Enfield muffler.
Note right-shift conversion, done to improve shifting..
In his ad he wrote: "I got the 2008 Enfield on a trade, took it for one ride with the stock 500 engine, came home and went 'meh.' The stock Enfield gave me no feeling..."

But "the Enfield was the perfect platform for swapping in a diesel engine, with the separate five-speed transmission; the main hurdle was making the adapter to mate the primary to the engine block — and about 100 smaller issues that were sorted out.

"Engine has electric start and starts with the stock starter button on bars, and has the kick-start as well just in case, but the upgraded charging system on the engine maintains the battery well.

Royal Enfield motorcycle with diesel motor.
Front disc brake is welcome as the diesel motor adds weight.
"I chose the Lombardini 6LD360 engine since I restore Italian tractors as a side gig, and have a lot of experience with that particular engine. Fully mechanical, parts are cheap, and easily rebuildable. Plus I had some extra engines laying around...

"That big plate on the bottom is a large capacity oil sump with cooling fins that I transplanted from a different engine; more oil capacity and better cooling. Overkill? Yes, maybe, but the bike was originally intended to be more of a scrambler with knobbier tires for some light off road and trekking, so slow moving — I wanted better cooling for longer life."

Royal Enfield motorcycle with diesel motor.
Big plate on bottom of motor is extra-capacity oil sump with cooling fins.
The motorcycle has effectively two mufflers, retaining the Lombardini box muffler and the Enfield muffler "to keep exhaust tone reasonable. The motor has a decompressor lever. Its electric starter is integral to the diesel motor, not the Royal Enfield's original.

"It will not go on highway geared as-is," Anthony wrote in the his ad. "Would need to change rear wheel sprocket to get highway speeds. Bike with current gearing runs at 52 mph, and has tremendous torque down low. Original intent was to make it a scrambler, but after it was running and on the road kept it as it is."

Royal Enfield motorcycle with diesel motor.
Air cleaner and spin-on oil filter keep "Dirty Diesel" clean.
Fitting stock primary was the most challenging element of conversion.
In an email to me, he added this:

"About the gearing — I originally had very tall gearing for the bike to do 70, but within a week I burnt the clutch plates out. It was just too tall to pull away and the torque of the diesel was way too much for stock plates. So ordered heavy duty plates and springs from Hitchcocks, and lowered the gearing, so now its very easy to pull away and ride around but the top speed is limited to a little over 50. My next step was going to be new rear wheel sprocket and O-ring chain, but I got other bikes to feed.

"The engine is heavier than the stock RE 500 gas motor. This is an understatement. The engine is indestructible and weighs like it is.

"Shifters, foot rests, rear brake were all slightly modified... The right-side shifting is so much more exact; the American left-side shifting has the long cross shaft and a long foot lever on the end of it, any play is magnified and it feels so sloppy and false neutrals were common.

"Getting a false neutral while downshifting for a red light on a 500-pound diesel British bike is frightening. So switched to right shift and all was resolved," Anthony wrote me.

"This bike is titled, registered, insured, and running on the roads in New Jersey," his ad notes. "There are not many street-legal diesel bikes in the U.S."

Here's his video of the motor running.


  1. Beautiful Conversion - amazing actually. He was lucky to bypass the Taurus. They were cool but had performance that was too poor to be of much use here.

  2. Including the diesel, here are the Indian-made Royal Enfields featured on your site: a '99 with 604mi, a '95 with 377mi, a '95 w/sidecar with 7,000mi, a 2008 diesel with 600mi, a 2000 with 4150 miles, another 2000 with 8580 miles, a 2008 with 10,000 miles and a 2018 with 500 miles. I've refrained from calculating mi/year. I don't get it, David, didn't these people have to PAY for their motorcycles? Didn't they buy them to use? It's baffling and dismaying. Maybe they each own several Italian exotics and only use the Enfields to chase parts...

    1. I have often wondered. All I can think is that these owners may have several motorcycles to choose from, busy work schedules that keep them off the road, live in states with long winter lay-ups, or perhaps the Royal Enfield suffered some minor problem (broken turn signal?) that was left unattended until inertia set in.

  3. That's certainly thinking the best of those folks. Probably there are as many reasons as there are almost-no-miles Royal Enfields. You're a better guy that I am, David. I wonder: Why own one if you don't ride it?

  4. Bharath8/30/2022

    How is the vibration on it ? Like does the stock Enfield frame handle the shock ? And do you actually need a starter motor for the diesel engine. I'm planning to build an engine without a starter motor and starts just by the kick. Do you think diesel can achieve that ?

    1. Anonymous3/27/2023

      I now own the bike in the article. It will kick over but it takes a special technique of 'bouncing' against the compression a few times to presumably build momentum and some cylinder temperature. She rattles, she's loud, she stinks, but it's a blast!


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