My lohmann engine; a tale of woe



My lohmann nolonger runs. It was in perfect running condition on a beautiful old bicycle. I have good memories of riding with it running . I put this combo together in 1982. It was very low powered, wouldn't push me up a hill without help. I really liked it being sort of a diesel. I stored it in a friend's barn. While I was on a year long trip, the barn burned down and melted alloy parts off the motor and ruined the antique bicycle it was mounted on. I kept the remains hoping to someday find replacement parts. No luck sofar. I had an ownersmanual as well, it totally burned up in the fire. The bicycle was british racing green, with a Hong Kong Bicycle co. decal, a front hub generator, rod brakes, and a 3speed rear hub with a coaster brake, 28X1 1/2 inch wheels, comfy leather saddle and a locking front fork. I bought this bicycle from a man who at one time had been the British Consulate to Hong Kong. He only rode the bike 3 times because he said that Hong Kong was too hilly. It was really very heavy for the little Lohmann to push.




Well, there is always a new engine, truly, the scarcity myth need not apply, technology is on the march, rampant.




Wow man thats rough, I really hope you can get your hands on some parts and restore it to its former condition. Didn't those motors run on all sorts of different fuels?



more Lohmann info

Here are two patent drawings of this engine:

This is an 18cc compression ignition engine. the controlls consist of two twistgrips. one controlled the fuel and the other controlled the variable compression ratio via a movable cylinder head. Lohmann claimed up to 300mpg for this motor. Maybe that was possible if you only went downhill. This is a 2cycle engine and was designed to run off of a light distillate mixed with a measured amount of lube oil. There was a nifty measure for the lube oil built into the fuel tank cap. I usually used kerosene in mine but stoveoil or diesel #1 worked too. #2 diesel seemed a little too viscous. The engine made a buzzing sound when running and left a little trail of smoke behind it. I don't have any surviving pre fire pictures of my bike and engine but here are a few of a bike that is in a museum in Europe.

This last picture show the twist grip that contolled the compression. It had two cables that went down to the engine.



If my lohmann were in running codition I would have tried it on biodiesel by now. I have been using various mixes of biodiesel in 4 different turbodiesel Mercedes and one Ford diesel truck as well as a diesel generator for the last five years.


Minnesota Hyena

lol 18 cc diesel??? that's smallest diesel engine i have ever seen.
that engine is so small, yet enough to pull bicycle which is amazing.



It is a diesel in the sense that it is a compression ignition engine( no spark plug), but it doesn't have an injection pump or fuel injector like a conventional diesel engine.



try looking on ebay france for engines as i brough a couple of lohmanns at less than 50 euros each from there last year not complete ones though.i just brought an itom motor only item no260075717133 which was a lot better price than the one i was looking at in the uk 150083851575.although the uk one was more complete it was not worth it.



Man thats really sad :sad: I've restored some really destroyed machines before, one Cyclemotor from the 20's was basically this bad. and it runs now, so nothing is impossible. I do some aluminum casting, and machining, so with some help ya never know. I live in Puyallup so we aren't too far apart.



lohmann bicycle engine

Dera psuggmog
> I am writing from India, suffer from an obsession with the Lohmann, and acquired a Lohmann in
> incomplete and worn out condition last year. I have
> been working on it for last six months and have
> restored it to good working condition. I have honed
> the cylinder 0,2 mm oversize and made a new piston
> and
> rings locally. I have also made some changes in the
> original design to improve performance. It runs best
> on kerosene/5 % 2T oil mixture. It starts easily,
> runs
> with low noise and vibration and idles at low rpm
> smoothly. It has ample power to run a bicycle with
> single rider at 30 kph at half throttle. I have
> diagrams and operating instructions. If anyone needs
> any help for restoring or building a Lohmann[a
> skilled
> model engineer can take it up as a project], or with
> spare piston and rings, or has any experience with
> running the Lohmann on bio-diesel or vegetable oil,
> please contact me.

At last after six months of hard work I am able to
enjoy the smoke and the noise of the Lohmann. It has
taken a lot of running in to get it to run without
overheating and stopping. I ran it at idle without
load using a table fan for upto an hour at a time.
Once I am able to run it for an hour, it idles at low
rpm smoothly. Starting is extremely easy, only one
attempt is usually necessary, even when starting the
first time in the morning. The throttle is very
sensitive, the slightest pressure is enough to speed
up or slow down.

I have replaced the original toggle lever for engaging
the roller with another arrangement which works much
better. I found that the original toggle arrangement
gives only two positions of the roller-engaged and
disengaged, while you need three-for starting when the
wheel is driving the roller you need high roller
pressure to prevent slipping, but this pressure needs
to be reduced for normal running when the roller is
driving the wheel, otherwise it overloads and slows
down the engine. The third position is of course the
disengaged position. I have fitted a 2 feet long
lever made of 6mm dia steel rod to the cylinder head
plate, so that it comes up to the level of the saddle.
Taking advantage of the engine being mounted on a
pin, if you move the lever forward it presses the
roller hard against the wheel- for starting. In the
middle position, it presses the roller lightly just by
its weight and the pressure is enough to run the bike
without overloading the engine, even if the wheel is
not running true. If you move the lever back, it
disengages the roller ! Not only it works well, but
you can operate it while cycling, sitting on the
bicycle seat, which is certainly an advantage.

The Lohmann is running beautifully-I can run for an
hour without stopping even once and restart easily.
I've fitted the air intake cleaner to prevent dust
going in. The sound with the spring muffler is quite
muted-a steady and pleasant purr. If the compression
is too low or throttle not opened enough for the
particular compression setting, the Lohmann four
strokes with reduced power and you have to increase
the compression or open the throttle till you get a
steady purr. There is a slight puff of smoke, maybe
because I am using too much oil for running in-10 %.
Kerosene seems to work best, better than petrol or
diesel-easy starting and plenty of power. While the
power is enough for normal running, if you have to go
up even a slight incline or slope, the engine strains.
Maybe a higher gear would be useful.

Now that its running well, I intend to use it
regularly and gain operating experience. Then I'm
wondering what to do next !

> Akhilesh Agarwal
> Mechanical Engineer



Akhilesh, thanks for the information and inspiration. My Lohmann alsways ran the best on kerosene as well. The main castings which enclose the reduction gears are warped and deformed due to heat damage. The Mounting lug for the engagement lever melted away. I am interested in any technical details of your restoration you might wish to share. I have the ability to machine parts as needed.



Lohmann restoration

Dear psuggmog,
Nice to hear from you. Where are you located -Washington, USA ? I am located at Lucknow, India. I will be happy to share all my restoration technical details with you. The fact that you can machine parts yourself is a big help, I resume you have your own machine shop and measuring equipment.

I have worked on my Lohmann for over six months to get it going, and have learnt its intricasies the hard way. My Lohmann was incomplete[without controls] and worn out, but one that is damaged in fire is another question-far more difficult and needing replacement /making of lot more parts. I wouldn't worry about the mounting lug for the engagement lever because its easy to fix and I changed it anyway. If the castings which enclose the reduction gears are warped, it should be possible to repair it either by making fresh ones from aluminium plates or by sand casting aluminium-I've done it and its not that difficult. Are the reduction gears ok ? The main thing I'd worry about is that the reduction gear casting is integral with the crankcase-is that damaged/warped ? You need a good crankcase and crankcase cover to get proper alignment of the main bearings for the crankshaft and a good seal for crankcase primary compression. How is the aluminium cylinder block ? You will need to change all non-metallic parts such as oil seal and drive roller as they would probably have melted.

I will be in a better position to advise if I know the machining facilities you have, and if you have taken the Lohmann apart and describe the damage in detail.

Are you sure it is worthwhile to restore this Lohmann, or in case Lohmann's can still be found, simpler to buy another ? I understand thay were imported into the US by Macy and retailed by Gimbel.

If you are prepared to put in the required time and effort, I will be happy to assist you. Is there anyway we can exchange emails directly or do we have to post here ? My email id is

Best regards,