Solo Motors

Welcome to Solo Motor Parts department. 

Type 236/237 identified by no coolant fill plug

Solo Type 236/237 Engine
No coolant plug above spark plug

Solo Type 254/255 Engine
Coolant plug above spark plug

Solo Engines are made in Germany by SOLO Kleinmotoren GmbH, Postfach 600152, D 71050 Sindelfingen, Germany. Solo made mostly small agricultural motors, chain saws, sprayers, etc. The name is from the revolutionary backpack portable sprayer for pesticides in 1951. The “Solo” could be used by a single person for the first time, whereas in the past pesticide sprayers required a heavy stationary motor pump and several assistants to handle the long hose. See Odyssey, Solo for more.



Solo/Odyssey Engine Service Manual, edited cover.

Solo Mofa/Moped Engine Specifications

The specifications below are from the Odyssey Service Manual, 1977 edition, and from direct measurement. 

SOLO ENGINE Type 236 Type 237 Type 254 Type 255
================= ================= ============== ============== ==============
bore x stroke 38 x 43 mm same same same
displacement 48.7 cc same same same
compression ratio 8.3 : 1 7.5 : 1 8.3 : 1 10.0 : 1
horsepower 1.45 hp 2.1 hp 1.75 hp 2.6 hp
max torque 2.3 ft-lb 2.2 ft-lb 2.4 ft-lb 2.7 ft-lb
CYLINDER alum. w/steel sleeve same same same
cooling air cooled only air cooled only air + water air + water
transfer ports (2) left and right (2) left and right (3) left, right, rear (3) left, right, rear
cylinder size, new 38.00 (1.4961") same same same
PISTON Mahle 19 x 10 x 22 same same same
piston size at skirt, new 37.96 (1.4945") same same same
piston clearance range 0.04-0.06 (.0016-.0024") same same same
piston rings (2) type 38.0 x 1.5 side-pin same same same
ring gap range 0.02-0.05 (.008-.0020") same same same
top-edge-to-pin 19 mm same same same
piston pin 10 mm x 32 same same same
pin-to-bottom-skirt 22 mm same same same
needle bearing cage 10 x 14 x 13 same same same
CRANKSHAFT 5-piece type same same same
needle bearing cage 14 x 18 x 10 same same same
right (magneto) nut M10-1.0 (Ø90 flywheel) M8-1.0 (Ø80 flywheel) same same same
left (clutch) nut M10-1.0, 17 hex same same same
L+R ball bearings 15 x 35 x 11 #6202 same same same
right (mag) seal 15 x 25 x 5 15 x 25 x 5 15 x 35 x 7 15 x 35 x 7
left (clutch) seal 15 x 25 x 5 15 x 25 x 5 26 x 35 x 7 26 x 35 x 7
left seal function seals case to shaft seals case to shaft seals case to clutch seals case to clutch
clutch bearing seal 15 x 21 x 3 15 x 21 x 3 15 x 21 x 3 15 x 21 x 3
clutch seal function oil only, no pressure oil only, no pressure seals clutch to shaft seals clutch to shaft
CLUTCH single plate dry same same same
running clutch centrifugal automatic same same same
friction plate thickness 3.8 mm (0.150") same same same
clutch grab speed 2600 rpm 2850 rpm 2600 rpm 2850 rpm
starting clutch manual hand lever same same same
needle bearing sleeve 15 x 21 x 16 same same same
PULLEY and BELT Z-profile 10 x 6 same same same
needle bearing sleeve 16 x 22 x 22 same same same
GENERATOR (Euro) Bosch 0212-005-011 80mm clockwise M22-1.5 puller same same same
lighting coil (Euro) 6 volt 17 watt same same same
GENERATOR (USA) Bosch 0212-124-039 90mm clockwise M26-1.5 puller same same same
head light & horn coil 6V 22W, yellow wire same same same
tail light coil 6V 5W, grey wire same same same
stop light coil 6V 10W, green & grn/blk same same same
IGNITION magneto, blue wire same same same
points gap 0.35-0.45 (.014-.018") same same same
ignition timing 2.4 mm BTDC 2.4 mm BTDC 3.0 mm BTDC 3.0 mm BTDC
spark plug gap 0.5 mm (0.020") same same same
CARBURETOR Bing 1/10/112 same same same
venturi size 10 mm same same same
main jet Bing 3.5mm #58 same same same
choke system cable operated same same same



Clutch Seal: The pressure seal for the clutch side on the 254/255 is not just one seal, like normally. It is two seals, the outer one 26x35x7 seals case-to-clutch, and the inner one 15x21x3 seals clutch-to-shaft. This is the Laura clutch seal/bearing design, similar to Batavus. Instead of being separate in it’s own grease, the clutch needle bearing is bathed in the two stroke oil and gasoline. The benefit is it never needs to be greased. The drawback is the crankcase pressure has another place to possibly leak, both fresh air inwards, and fuel/air mist outwards. 


Solo Regular (1-speed) Transmission, no pulley screws

Odyssey Regular (1-speed) Trans.
A. has no pulley screws
B. disk clutch with start lever

Odyssey 2-Speed Transmission
A. has 12 pulley screws

Solo 2-speed first speed clutch

Odyssey 2-speed Transmission
B. has a 3-shoe auto clutch










How to identify a 1 or 2 speed: There are two types of belt-drive transmissions, 1 speed and 2 speed. The one-speed (ein-gang) “regular” transmission has a solid rear pulley, with no screws around the edge. The two-speed (zwei-gang) transmission has a rear pulley with planetary gears and a second speed auto clutch inside, with 12 screws around the edge. The presence or absence of pulley screws is the best way to tell a 1-speed from a 2-speed, from a few yards away. If the clutch cover is off, the presence or absence of the manual starting clutch lever is another way to tell. 1-speeds have it but 2-speeds do not. 



Solo “Odyssey” Motor, Type 254 and 255

Solo Odyssey motor

Solo Odyssey motor

with Laura disk clutch, or Solomatic shoe clutch (2-spd)

Odyssey 32/1 (20 mph) has Solo Type 254 engine

Odyssey 40/1 and 40/2 (25 and 30) have Type 255








Solo Odyssey Parts Manual Engine

1977-78 Solo Odyssey Engine Parts


More info about the Odyssey 2-speed: “Home Alone with Mopeds” has an excellent blog about the Odyssey 40/2-2 two-speed belt drive moped. An all original fresh condition bike is photographed and explained, inside and out. Included are pictures of the planetary gears, the second speed auto clutch, and the “secret” switch that allows backing up without turning the engine over backwards. Click here for a beautiful adventure and lesson on German engineering:

ColumbiasoloSolo “Colombia” Motor, Type 255

Solo “Odyssey” with Columbia-made clutch and no coolant

Colombia 2240-2250 clutch

Solo 255 with Colombia “belt clutch”.
The sides of the belt are the friction surface.
No clutch shoes, no friction plate or disk.

How the automatic clutch works: The engine is idling and the belt is stationary. The pulley sides are spinning, but the pulley center is not, because it is on a needle bearing. As the engine begins to rev up, the weights #6 fly out from centrifugal force. They force the outer pulley half #8 inward, causing the sides of the belt to rub on the spinning pulley sides. The bike begins to move forward. As the speed increases the weights fly out more and more. When the revs are high enough, the weights are fully out, and the belt is not slipping, or almost not slipping. When the bike slows down, the spring #7 pulls the weights back in, and the slipping process reverses.

How the starter clutch works: A manual start lever on the handlebar pulls a cable, that pulls a start lever #36 against the clutch. It moves a plates #3 and #5 inward. That forces the outer pulley half #8 to rub hard against the belt. Then moving the bike forward, either by pushing or pedaling, causes the engine to turn over, and hopefully start up (if other things are working). When the start lever is released, moving the bike forward has no effect on the engine.


Solo Colombia Engine Parts

1979-80 Solo Colombia Engine Parts



More clutch info: The Colombia “belt clutch” has a needle bearing in the front pulley that allows the belt to be stationary while the engine crankshaft is spinning at idle speeds. Those needle bearings often go out, and bind. Then the bike won’t stay idling unless the rear wheel is allowed to rotate at around 5 mph. The thin needle bearing needs to be greasy, inside, but the belt that goes around it needs to be not greasy.

Colombia pulleys inboard side view

Columbia pulleys
inboard side view

Colombia pulleys outboard side view

Columbia pulleys
outboard side view

Colombia (Solo) front pulley needle bearing TR0414P520518 made by Koyo

Columbia (Solo) front
pulley needle bearing
made by Koyo

Colombia (Solo) front pulley needle bearing TR0414P520518 made in USA by Koyo

Columbia (Solo) front
pulley needle bearing










Another problem is high friction. As explained above, the sides of the belt are the friction surface. The trouble is, the design causes a lot of friction, so you have to push or pedal really hard. The excess friction is from the belt rubbing the pulley sides the wrong way. The belt only moves in a circular motion for half way around, then it moves across the pulley, not with it. Some people are not strong enough to get it started.

Another problem is slippage. The sides of the belt always slip a little, but they slip a lot when greasy. Then you have to pull very hard with your left hand on the start lever. The hard squeeze required eventually leads to the starter pieces wearing out fast. Once that happens, some people end up wrapping a rope around the flywheel to use as a pull starter. De-greasing the belt, and applying sticky spray for squealing belts, should help it to not need such a strong squeeze on the hand lever.



TasMoprixTas BE-48, Solo Type 237 clone

with Tanaka-made “belt” clutch (no plate or shoes)

Tas BE-48 engine remake of Solo 237

Tas BE-48, a Japanese remake of Solo 237

Solo Type 237 clone

Tas BE-48, Solo 237 remake engine
1980 Moprix, made in Taiwan by Pou Yen













More to follow…


1990’s Solo Mofa/Moped Motors


1994 Solo 712 or 713 (Euro model) Owners Manual Parts List

1994 Solo 712 or 713 (Euro model) Owners Manual and Parts List



The 70’s bike, 20 years later.

Modern gel seat, modern controls, no more chrome, aluminum wheels that resist bending.

Same engine, frame, exhaust, fork, etc.

Same loose ball and cone wheel bearings.

“Euro version” floor boards, lights, and bell.

Solo Hydro-Drive

Solo 1990’s Hydraulic Clutch “Hydro-Drive”