| Technical Info |  |
New articles are always welcome. The aim of the web site is to provide information & help in the restoration & running of the Adler. Engine rebuild Details provided by Rowan Bond in Australia. Kawasaki A1 Samuri con rods are almost exactly the same length ( slight increase in compression ). If your pistons are too worn, obtain a set of Suzuki GT250 pistons and rings which are perfect except for a very slight loss of compression ( see con rod length ). Modern bearing and seal sizes for the crankshaft are:- Seals for the crank are 3 of 25x40x8 p/n PR8094 and 1 of 20x35x8 p/n not known. I did have problems sourcing the seals for the kickstart and gear selector shaft which are 17x27x7 and also the fork seals which are 22x32x7. HINT, When you pass the left hand crank shaft through the centre bearing and seals make up a gadget to lead the crank through the seals ( wood or metal shaft ) with a spigot to go into the threaded section and the outside diameter slightly larger than the inside diameter of the seal or the Hirth coupling teeth will tear your seals so shreds. Exhaust design Different outlet diameters ( using plugs at the end of the pipe ) , were tried with the following results :- With modified ports and heads , the motor produced 36 HP with maximum revs of 12000 with 14:1 compression , running on methanol and achieved a top speed of 120 mph. John Wynne the builder of the car, is now retired to the Gold Coast in Australia but the Adler powered car still resides in his garage. Ignition coil replacement Firstly the charging system. The original Bosch regulator is sited at the front of the ignition setup of the motorcycle under the right cover. Coil replacement. The coils failed shortly after this modification and that presented much more problems. I removed the coils and had them tested. Having looked around, I found a couple of neat coils off a Honda CB100 which were black, would fit under the tank and easily mounted off a fabricated bracket attached above the front tank mount. Wiring detail from the original owners manual is included for your information. I considered making up dummy HT leads to look original, however Adlers are so rare, no-one has picked up the modifications in 14 years. |
Coil upgrade ( alternative method )
Further information on coil replacement by Don Littleford.
The Adler` coils are mounted inside the right hand engine cover and are subjected to heat and tend to fail as they get old.
I was trying to keep my bike as original as possible and had my original coils rewound after they failed.
Epoxy was used but this is not a cheap option.
However the rewound coils worked well although they were still mounted inside the motor.
I had previously converted my MB 250 to upswept exhausts so there was a convenient mounting point under the seat for the coils.
The conversion to upswept exhausts required the removal of the " saddle spring cover plate ", Part 358 in the Adler spare parts list.
The first thing to do was to find suitable 6 volt coils.
Several models had been recommended so I went searching at motorcycle shops and bike wreckers.
I found modern coils sold in Australia by MCS.
They supply to most distributors / wreckers but if you cant find a agent, contact them direct at 07 3375 6600, mobile 0427 013 256 .
The coils are manufactured in Taiwan and are used extensively for battery, coil, points system.
The 6 volt coils in their catalogue are part number CH4 ( CB 100 K4).
There are other coil options and another owner advised his bike is using external Bosh TL3/1 coils.
The Taiwanese coils are shown in the photo. Stamped FL 801-6V.
It is important that coils for battery coil points ignition are used as others ( CDI ) will not work on the Adler system.
You therefore need a coil with three leads. Power in, power out to condenser / points, and a spark plug high tension lead.
I had to change the connectors as I could not find ones to match those on the coils.
The CH4 coils were not marked with + or - , although I was told by the supplier that the black wire with the male connector was to be used for power in.
This makes sense, as it would mean that the power wire from the battery would have a female connection and would be safer if ever the connection came apart, there would not be a live wire to short out on the body.
With the -ve earth Adler it is essential that the +ve battery connection goes to the +ve connection on the coil.
If there is any doubt as to the performance of the existing condensers mounted adjacent to the existing coils inside the motor they should also be replaced.
It is recommended that the existing condensers also be replaced.
These can be located beside the new coils in the air flow.
6V condensers can be easily obtained from a auto electrical shop
Mounting of the coils under the seat in my case was relatively simple by manufacturing light brackets ( refer photo ), while making sure the coils were earthed well.
If mounting under the seat, make sure that the seat will be clear of the coils when installed.
I used heat shrink on all connections to make them secure, and 5 core flex ( used for trailer wiring ) , as I was still going to use the existing high tension leads hole in the engine case to access the internal points.
Needing only 4 wires I just cut off the unwanted one.
Before the new wiring was connected I isolated the existing coils in the motor.
This involved removing the high tension leads and the connections between the coils and the condensers.
As I was going to used the existing condensers , the wires between the condensers and the points remained.
If the condensers are old they should also be replaced.
I wanted to keep the existing coils in place as they were still working and would be available if any future owner of the bike wanted to go back to the original wiring.
It would be a simple process to rewire the coils back into the system.
The wiring inside the motor is as follows, you can refer to the image ( click for full size ) for more detail :-
- Connect the four wires to coils and feed them through the grommet to be used to seal the case.
- Disconnect the power wire from the backing plate ( terminal 5 in diagram ) and connect to the two black power wires to the coils. Don`t use the existing screw attachment as this will mean power remaining to the existing coils. I just joined the three wires and tucked them into the space behind the backing plate.
- Connect the remaining two blue wires to the existing condensers, making sure you match up the wire from the left coil to the left cylinder condenser ( left to 7 and right to 14 in the diagram ).
- Connect the high tension leads to the plugs. I used plug caps that just screwed into the high tension leads .
That`s all there is to it.
The bike should start and the coils will no longer be affected by heat .
Ignition timing. A simple but relatively accurate method
Equipment needed :-
- T section of dowel to measure depth of piston ( depth indicator with handle ) .
Leg that goes into the plug hole being approximately 70 mm. See comment below - Timing disc socket made out of plastic protractor glued to 14 mm socket
( you don`t have to remove the 14 mm bolt holding the electrics on ) . - 6 v test light to go across points .
- Pointer which is attached to the motor case using an existing bolt hole and that can be bent so that it will be close to the timing disc edge .
- Wire or light metal is adequate.
Photo 1
Procedure :-
Remove spark plugs from both cylinders .
Adjust contact points gap for each cylinder . ( 0.3 - 0.4 mm ) . ( see note below ).
To time left cylinder .
Put dowel depth indicator down the plug hole .
Hold handle of T firmly against the cooling fins on the head and turn the motor over with a spanner on the bolt head until the piston touches the dowel .
Piston can be rocked back and forth with the spanner to get an accurate position as you can feel the piston when it touches the dowel .
The disc socket and the bolt head have a mark so that the disc socket is always put on the bolt head at the same location . ( see photo`s 1 & 2 ) .
Put the timing disc socket onto the bolt head and take a degree measurement against the pointer. Record this degree `A` .
Photo 2
Take into account for any free play between the disc socket and the bolt head by turning the disc socket clockwise against the bolt head with a little pressure ( make sure you don`t rotate the motor ) , before taking the degree measurement .
Do this before taking any readings .
If the disc socket fits snugly with no free play then there is no need for this
The 70mm depth will give a location of the piston approx 30 degrees before TDC.
Remove the disc socket and rotate the motor as before to go past TDC .
The dowel depth indicator rises out of the cylinder and then drops again .
A shorter depth than 70mm OR a dial gauge, will give a more accurate reading. For greater accuracy, use a spark plug with the internals removed. Make a hole down the centre of the spark plug to fit the gauge.
When the handle of the T sits on the fins again take another degree measurement with the disc socket .
This gives the same position of the piston after TDC . ( approx 30 degrees as before ).
Make sure the disc socket goes on the bolt at the same position .
Record degree `B` .
The difference between the two degree readings A & B on the disc gives a degree reading for TDC .
Make a note of this reading `C` .
Work out the degree reading you need on the disc for correct timing before TDC .
( MB 250 is 22 degrees before TDC ) . Reading `D` .
Rotate the motor by turning the timing disc so that it reads the correct degrees before TDC
The piston in the left cylinder in now set at the correct position before TDC .
It is this location that the ignition points should be just opening .
Photo 3
Loosen the three adjusting screws holding the backing plate to the engine body .
The screws should be loosened just enough to let the backing plate move .
If the backing plate is too loose the plate will rock and alter the points gap .
Without moving the piston from this position install the test lamp across the points for the left cylinder and turn the ignition on .
When adjusting the motor with the ignition on it is best to short the high tension leads out against the body so as to release the spark built up in the coils .
Adjust timing by rotating the backing plate to get the points to open at this position of the piston.
The test light comes on when the points just open .
Tighten up the screws holding the backing plate to the motor and recheck.
The left cylinder is now timed .
If you cant get the points to open with the backing plate fully rotated against the stop, then open the points a little bit more than the 0.4 mm as specified.
This problem is the result of normal wear in the system
Do the same with right cylinder but make the timing adjustments by moving the right cylinder points where they are mounted onto the backing plate and not by rotating the backing plate .
This would change the set up for the left cylinder .
See photo 3 .
Undo screws A and B and adjust with cam screw C .
It is important that small brass washers be placed under screws A and B .
Otherwise when tightening up these screws the small plate tends to move against the backing plate and the timing will be wrong.
The motor should be run and the timing rechecked .
Depending on the condition and wear in the motor , the timing should not have changed .
Repair of broken air cleaner lever
A self tapping screw will be used to realign the outer ring with the main air cleaner body and the offset carburetor air inlet tube when re-assembling the air cleaner ( photo 13 ). |
Photo 4 shows that the drill holes go through the air adjusting vents. |
Remove the filter meshes using a hook wire puller
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The outer ring should come apart from the air cleaner body.
If not, the outer ring needs to be cut and pried apart
( arrow photo 5 & photo 6 ).
After removing the outer ring the air cleaner body needs to be cut with a thin blade all the way around to remove the inner ring.
A thin cut is necessary as the inner ring will be soldered back in place and there has to be sufficient space for the filter meshes.
The inner ring and main body can be marked so the inner ring is put back in the same position.
The vents were held in place by the 4 spot welds which have been drilled out. |
The vents are replaced inside the main filter body and the fixed vent is spot soldered into place.
Make sure the lever is in the correct position and the adjustable vent moves freely for the full length of the slot.
The inner ring is soldered back ( right around ) and the mesh filters replaced.
and repair the drill holes in the outer ring.
Align the filter and insert a self tapping screw.
Final filter assembly
Parts of the filter can be chrome plated before assembly.
Chrome the lever only and not the vents.
When restoring the Adler motor, there is a problem in that the original pistons are rare and difficult to find.
There are other options and some other brand pistons are readily available.
What we need is a piston that is as close as possible to the dimensions of the original.
The original Adler pistons for a standard 54.0 mm bore are :-
Adler YD3
Total length ( incl dome ) 70.0 mm 69.9 mm
Dome 3.0 mm 3.0 mm
Gudgeon pin diameter 15.0 mm 15.0 mm
Distance from centre of gudgeon pin to lip of piston 30.0 mm 30.1 mm
Diameter for standard piston 53.96 mm
Weight ( piston only ) 175.0 grams 170.0 grams
Note :- If using the YD3 pistons the clearance between the bottom of the piston & the flywheel should be checked.
It may be necessary to trim a small section off the skirt of the piston.
Pistons with almost the same dimensions of the original Adler are :-
Mahle:- Available from Motorrad Stemler in Germany, weight 165.0 grams
Yamaha YD3:- Available on E Bay. YD3 bike in early 1970's, weight 170 grams
Yamaha DS7:- Rarer with 16 mm pin and lighter at 145 grams
These piston sizes start at 53.96 mm and increase in diameters by 0.25 mm.
The dimensions of the readily available YD3, 2 ring piston are shown in red above.
The 53.96mm Yamaha YD3 standard numbers are :-
Piston 148-11631-00-96
Rings 148-11610-00
Gudgeon 148-11633-00-00
Other options include the Suzuki GT250X7.
However these are 5.5 mm shorter, 10.0 grams lighter and have a 14 mm pin.
While the lighter weight is not a problem, as the flwheels / conrod / piston are usually balanced during assembly, the shorter length does affect port timing.
This results in the power comes in at higher revolutions of the motor and therefore affects low down accelleration, hill climbing etc.
Crankshaft drawing
