16 HP Adler MB250 motorcycle engine & 18 HP Adler MB250S engine

The Adler engine is a 250cc air cooled twin cylinder two stroke with nominal bore and stroke of 54mm, and compression ratio of 5.75:1.
It was made in Germany from 1954 to 1958.

Both the 16 and 18 HP motors share a common conrod, small end bearing and wrist pin.

crank rods -Click on an image to enlarge it.

The bigend bearing was a bronze-caged roller bearing with 12 of 5mm diameter rollers each 8mm long.
The bigend hole in the conrod had a diameter of 32.39mm.
The little end hole had a diameter of 18mm and carried a bronze bush for the 15.0mm diameter wrist pin.
The conrod is 107mm from centre of bigend to centre of little end bearings. This is almost twice the 54mm stroke of the motor.
The early 16 HP rods were approx 14.6mm thick and both the big end faces ran against the crankshaft webs.
The later 16 HP rods were approx 13.6mm thick and the outer big end face of the conrod ran against the crankshaft web while the inner face ran against a 1mm scolloped washer.
The 18 HP rods were approx 13.4mm thick and the big end faces ran against 1mm scolloped washers on both sides of the conrod.

rods rods rods rods
These are the original Adler drawings. Click on an image to enlarge it.

In the 16 HP crank, the big end bearing surface was a hardened interference-fit tube over a softer crank pin.
The 18 HP crank has a one piece stepped crank pin.
The soft big end pin of the 16 HP crank was 17.0mm in diameter, and the diameter over the hardened tube was 22.4mm
The big end pin of the 18 HP crank at the crankshaft web had a diameter of 19.0mm, and the diameter over the bearing area was 22.4mm


Adler MB250 Conrod Kits

A company in Germany sell conrod kits for the MB250 engine, and the Favorit/Sprinter engine.
They are: PRAEZISIONSWERK BUEREN

They offer a 17mm or a 19mm bigend pin and needle roller little end of 15mm or 16mm
The needle roller bearings are: bigend - 24x30x13, 15mm little end - 15x19x20 or for 16mm pin - 16x20x20.
The bigend pins are 24mm OD.

conrod-Click on the image to enlarge it.

The small end needle roller bearings are available in Australia from Timken - K15X19X20, ( or K16X20X20 for 16mm ) at around $20 ea

The big end needle roller bearing is available in Australia from Timken - K24X30X13 for around $35 ea

To contact the German company, email: praezi-bueren@t-online.de
Your contact's name is Oskar von Bohuszewicz
He understands English. Email him with your requirements and
he will respond with an offer Invoice.

conrod invoice-Click on the image to enlarge it

He requires the full amount in his hands, and since his Bank charges him
a fee to receive the Telegraphed Transfer, you will need to add 10 Euros to the amount sent.
To proceed, Telegraph the required Euros to his Bank:
VOLKSBANK PADERBORN-HOEXTER
2 NIKOLAUS STRASSE, BUEREN, 33142, GERMANY
Their Swift Code is: DGPBDE3MXXX
and the Account name is: PRAEZISIONSWERK BUEREN
and their address is: 31 BRILONER STRASSE, BUEREN, 33142
Their Account number is: DE65472601218103875500
Their Phone No is: 02951-2308, Fax: 02951-5928
Your Australian bank will charge you $A30 to execute the Transfer.