converting to diesel

trucker9710-4 /

I want to convert this new 78 motobecane i aquired to diesel. I am sure it is possible some how. any ideas? My turck is diesel and it would be very convenient to have all my vehicles run on the same fuel.

Re: converting to diesel

they do make Small diesel engines in India. Ethanol is easier than diesel because diesel ignites from heat of compression, not spark ignition. Diesels usually run compression ratios in the 14 to 22:1 range. gasoline 7 to 12.5:1. Diesel engines do not have spark plugs because diesel fuel ignites at a much higher tmperature than gasoline. the heat of the air in the combustion chamber literally EXPLODES the diesel fuel being injected into the cylinder begining at about 10 btdc. air and gasoline are mixed before they enter the cylinder on a gas engine and are burned by spark ignition varying between 10 and 25 btdc depending on engine rpm. Diesel engines generally are much heavier than gas engine of the same displacement because of all the extra moving parts (high pressure 1000 to 5000 psi <!!!>fuel injection system, cams, valves<even 2-strokes like detroits>, gears ect...) and the heavier duty constuction of parts like pistons, cylinders, ect...

GM tried to convert a gas engine (5.7l, or 350 cid olds) into a diesel. was a horrible failure. the only thing good that came of it was that when you converted the engine block back to a gas engine, you could build the shit out of it!!! could bore (.125" over!!!) and stroke (could use an olds 455 crank) and make it into a 425cid small block!!! go around telling people it was 'just a 350..." after you whuped their ass in a drag race...

Re: converting to diesel

david f martin /

Faust! Get ahold of yourself, man! We're talking about a moped engine!

Trucker, seems like I've heard about a small diesel engine, but I don't remember from whom... do a search...


Re: converting to diesel

See if you can find any information on Lanz tractors, they used two stroke engines (huge two stroke engines) and burned a mix of diesel and kerosene. They didn't have sparkplugs, but they did have hot bulb ingnition (kinda like a glow plug)

Re: converting to diesel

'hot bulbs' and glow plugs are only used before the engine is started to preheat the cylinder. kerosene is also known a 'diesel #1' because it is basically 'diesel #2' with the 'waxes' and other lubricating chemicals that are part of the fuel removed. it 'gels' or starts thickening to a Jello consitancy at a lower temperature (-40 F versus -20 F). They Probably use Detroit Diesel Engines. Detroit (GM) has been making the same basic engine design since before WWII. they were used in WWII American tanks, and most American tanks until the M-1 which uses a 'gas' turbine (still burns diesel, but can burn about any hydrocarbon based fuel.)

Back in the 60's and 70's, 'hot rodders' started modifying 4 and 6 cylinder Detroit 'blowers' to use as superchargers on Gasoline V-8 engines. On the diesel engine, it is used to do what the crankshaft does on a small gas 2-stroke, and 'push' the exhaust out of the cylinder while filling the cylinder with fresh air. the incoming charge is around 4psi, so it's not considered 'supercharged.' In a 'supercharged' engine, the cylinder is filled with a charge at least 7psi above atmospheric pressure. The '92' series Detroits (all 'V's', V-6 or V-8, 92cid per cylinder) used a TURBOCHARGER feeding into the'blower' to supercharge the engine.

If you truly want to be bored to death about how diesels work, e-mail me. Spent about 1/4 of my classes in Auto diesel tech on How diesels work. Cummings,Caterpillar, Detroit,Mack, and the 'off-brands' like Lister (air-cooled 4-strokes), GM, Isuzu, Mercedes....

The U.S armed forces have them

I have seen diesel 2 cycle motorcycles before. I know U.S. miltary is using them because they can run on any oil source. Rokon makes two wheel drive all terrain motor cycles and some use deisel engines. i don't know if they are two or four stroke though.

Re: Forum Knowledge

I'm contstantly amazed at the volume of knowledge here in the forum. Wow.

form engines to history. Kudos to everyone. I learn so much here.


The US military does NOT have 2 stroke diesels.

Those are 4 strokes.

And there isn't one useful bit of info in this thread about converting any small 2 stroke gas motor into a diesel.

Re: Wrong

they still use 2-stroke Detroits. Use more 4-stroke Cummings.

don't go in tanks, mostly in 1 1/2 to 5 ton vehicles... lived next to Fort Bragg when I sold cars. Got to see 'em every day.

Re: Wrong

Try paying attention.

He said 2 stroke diesel MOTORCYCLES.

The only two US military diesel motorcycles are 4 stroke Kaw. and Rotaxes.

Re: Wrong

the reason you don't see alot about converting a small engine to diesel is because of how hard it would be. re-read the post I wrote about how bad it went for GM with the 5.7 Diesel.

Re: converting to diesel

Nope not Detroit engine, just basic crankcase induction two stroke single cylinder design. They were copied in Britain by a company that sold them as "field marshal" tractors, which you would crank it over by firing a shotgun blank that was loaded into the cylinder head.

Re: converting to diesel

also there is no such thing as a carburetted diesel. they are all fuel injected, the reason for this is because diesel dont produce vaccum. so you literaly have to shove it in to the cylinder.

Re: converting to diesel

the reason Diesel engines are injected is not only the lack of vacum, but the fact that the heat of the air in the cylinder is what actually ignites the fuel. No spark plug. the injector (in one without glow plugs) is where the spark plug would be. glow plug diesel engines have a 'pre-combustion chamber' inside the head where bothe the injector and the glow plug are at. the glow plug is only used before the engine is cranked.

the fuel is injected right before TDC and explodes, forcing the pison down. this is also why diesel engines are built so much 'sturdier'. they have more compression pressure, and stronger 'shock waves' to deal with. pisons and cylinder walls are built more like modern gas racing engines. high nickel steel blocks instead of cast iron. forged aluminum pistons instead of cast. forged steel rods instead of cast iron. forged steel crank instead of cast iron. things lke that.

Re: converting to diesel

I remember my folks driving our 1981 Oldsmobile Cutlass Cruiser with the 350 diesel. We had to yank the entire engine at about 40,000 miles after blowing numerous head gaskets and whatnot. And would you believe that the 350 diesel's horsepower rating was only 105!?!

I'm sure the torque rating was higher than the gas variant, but wow...

Yeah, those GM diesels were not designed as diesel engines -- GM just threw together some diesel parts on pre-existing gas engines and cranked out cars for those seeking fuel economy. What a joke!


Re: Wrong

Damnn dude

sorry... my bad

hooked on phonics worked for me

Tits on a bull

Assuming it is even POSSIBLE to convert your Motobecane (and it hasn't been established that it is) it would probably cost ten times more to do than your entire bike is worth.

What's the big advantage of having everything run on the same fuel? Are you planning to go on a campaign somewhere and will have a fuel truck in tow? Are you going to convert your outdoor grille, kitchen stove and water heater to diesel while you're at it?

Better yet, maybe you could convert your moped to atomic power. Then one little chunk of Uranium-235 could keep the sucker running for the next 100 years without refueling! That probably wouldn't be much more difficult than converting to diesel. And would make about as much sense.

If you really don't like your gasoline-powered moped, I'm sure you can find someone to take it off your hands for you.

Re: converting to diesel

see the lights on a moped subject!!!! quick

Re: Diesel Mopeds


Gotta chime in on this one! I ran diesel converted Tee Dee .049s on my radio controlled planes! They would use carbeurators and reed valve induction, due to a specialized head from Davis Diesel Development, which went out of business in the 1980s. It is possible, and I would buy a diesel moped if it were available, Happy machining!

Re: Diesel Mopeds

Now that I think about it there have been diesel bike motors. One was the 18cc (that's right 18cc) lohmann, which had variable compression. Now they're pretty old and very rare engines.

Re: Diesel Mopeds

little engines like that "diesel" in the first place. they use a glow plug to heat the head up and use 'heat of compression to fire the cylinder charge. probably just changed compression ratio. Gets more complicated the larger the displacement. Kinda like quantum physics. 'string theory' is the latest one trying to resolve the math on an atomic level with the math on a cosmic level. both have been using different math for as long as there has been science. string theory tries to resolve it, but still isn't a 'universal' equation, yet...

Re: Diesel Mopeds

david f martin /

Geez, Faust, why do you always wanna make things more complicated than they already are?


Re: Diesel Mopeds

dunno, my girlfriend tells me the same thing, brother. Not trying to make things more complicated, just know too much bs. wish I didn't, my life would be so much more simple.

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