Technical Information

THE FOLLOWING INFORMATION HAS BEEN SENT IN BY ROWAN IN ROCKHAMPTON:

If your Adler Big ends and con rods are unserviceable, you can try and get new ones from someone in Germany (good luck), or you can stroll down to your local bike shop and try this:-

Kawasaki A1 Samuri con rods are almost exactly the same length (slight increase in compression).  The big end pins need to be reduced from 20mm to 17mm to fit the Adler flywheels.  If you are going to grind down the ends to make a double diameter pin, USE EXTREME CAUTION that there is sufficient radius or else they will break (as mine did).  the Adler Crankpins are actually 2 piece, so press off the sleeve from the crankpin and have the Kawasaki pin cut and bored to 17mm hole through the centre.  Press this sleeve onto the Original adler crankpin, and it works perfectly.  You can actually get 2 sleeves from one Kawa pin, which is good as the pins are quite expensive.

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).  Combination of piston and kawasaki rod brings compression back to original.  You have to relieve some metal from the bottom of the piston where the transfer cutouts are to clear the flywheels.  Standard suzuki Gudgeon pins are Ok but with the Kawasaki needle roller small end bearings.  Take caution that you order Suzuki pistons that are earlier than 1976 as they have 16mm gudgeons which compliment the Kawasaki con rods but 1976 onward have 14mm pins.  There are no available needle bearings to suit this combination but I made up bronze bushes for the little ends and have had no problems at all in 13 years of riding.

Modern bearing and seal sizes for the crankshaft  are:-

2 of Fag No NU304TVP2 C3 tolerance (20mm i/d)
1 of Fag no NU205E/TVP2 C3 tolerance (25mm i/d)

It is important to specify C3 tolerance.  I used standard tolerance originally, but the crank started tightening and squeaking (literally). After a tear down, the local FAG agent was kind enough to send the bearings away for testing as they appeared perfect.  The results were that C3 (slightly looser tolerance (30 micron I believe)) should have been used, as the Adler crankcases hold the shaft and bearings very tightly (being exquisitely made) and allowed no room for expansion when heated.  The outcome was that the bearings started to tighten upon themselves.  So C3 it is.

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.  They are available but you have to keep on the bearing suppliers back to track them down.  I would suggest you buy a couple of each extra to be on the safe side and put them aside.  they are very cheap.

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 sto shreds.  Unfortunately the first you will know about it is then the bike is attempted to be started and crankcase compression will be grossly effected.  the bike probably will not go, and will necessitate a teardown to replace the seals.

ADLER EXHAUST DESIGN.

 

Article from Phil Irvings book, Automobile Engine Tuning, published in 1962 ( Click to enlarge )
This drawing of the exhaust was provided by Adler in 1955 as a racing car using a Adler motor was being developed in Australia by John Wynne. The exhaust was the latest development from the Adler factory and was used on the 250 RS bike. The Adler motor had been installed in the racing car and different exhaust systems from megaphones, reverse cones and varying lengths of straight pipes were used in an attempt to achieve the greatest potential from the motor. The exhaust design provided by Adler , gave a huge increase in HP with the car winning its first hill climb outing. Different outlet diameters ( using plugs at the end of the pipe ) , were tried with the following results :- 32 mm for road racing with power band between 6000 - 12000 rpm . 18 mm for sprints with power band 4000 - 10000 rpm 15 mm for hill climbs with power coming in at 2000 rpm . 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. The motor was further modified by the use of pistons and special rings manufactured especially for the car by Repco in Australia. Repco were associated with the construction of the Climax engine used by Jack Brabham , the Australian Formula 1 racing car world champion . 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. John was a friend of Phil Irving ( Vincent motorcycle fame ) and collaborated on the articles in Phil`s books " Tuning for speed " and " Automobile engine tuning " ( Click to enlarge. PDF file )

For more technical information see - Michael`s ADLER Site

ADLER IGNITION COIL CONVERSION

In the interests of very neat and smooth appearance, Adler motorcycles had their ignition and charging system hidden behind the right hand side cover of the engine. The only external signs of the system were the two high tension wires appearing from a rubber grommet on the top right of the crank cases adjacent to the carb.

There is no argument that this made for a neat looking bike but almost 50 years down the track it causes major reliability problems with the model. Ignition and charging systems would rather be running in a cool place preferably in the airstream. Being hidden under the cover exposes the electrical system to dual problems being both out of the airstream and also having to contend with actual engine temperature at all times. No wonder they fail.

Firstly the charging system. The original Bosch regulator is sited at the front of the ignition setup of the motorcycle under the right cover. I have seen several that work properly, but a combination of age and heat render them useless. The regulator appears to be identical to one fitted to BMWs of the era, so a source of parts may be found. I didn�t like the placement of the regulator, so when mine failed, I sited a standard (cheap) VW type regulator under the dual seat. The wires were run from the harness in the battery box to the regulator neatly and hidden. I have had no troubles since fitting this regulator, and the instruction sheet that came with the regulator was easy to follow to wire up. Remember that the Adler is a battery coil ignition system so that a working charging system is critical to the reliability of the motorcycle.

Coil replacement. The coils failed shortly after this modification and that presented much more problems. I removed the coils and had them tested. The auto electrician deemed them dead, and I did not have a clue where to source parts (This was 12 years ago). I wasn�t sure I wanted to source the original parts anyway as it was only a matter of time before they would have failed as well. Cost of rewinding the coils was prohibitive, and then they would be back in the same hot place to cause problems once more.

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. Having fabricated the bracket in 3mm plate, I mounted the coils in the gap between the front tank mount and inside the valley of the tank (They are totally out of sight.) The coils are mounted one behind the other on the twin frame rails. Ensure the coils are well earthed. Wiring was accomplished, by removing the old coils, and adding quality connectors to the existing wires from the condensor and power wire to the old coil. This makes a total of 4 wires (make sure you use different colours to aid identification under the tank), which were routed back through the wiring hole in the crankcase under the carb cover. After liberal coatings of rubber grease, the 4 wires were slid into about 1 metre of black 7mm rubber tube which was then routed under the carb, through the drain in the front of the crank cases between the cylinders, under the front crankcase fins and up the left front downtube adjacent to the clutch cable. The new wiring hardly shows on my black frame.

Wiring detail from the original owners manual is included for your information:- Once the wiring is drawn up the frame, it is an easy matter to wire the new coils the same as they were originally wired for the Honda. IT is critical to ensure you have 6 volt coils for a battery coil ignition system as the majority of Japanese trail bike coils are either magneto or CDI ignition coils which WILL NOT WORK on the Adler wiring. Honda CB100, XL100, XL125, CB125, XL175 (K1 model only) etc of the mid �70s work fine and are readily available at wreckers. Yamaha also make some lovely battery coil systems but are much rarer. Suzuki and Kawasaki went to CDI arrangements very early in the piece and are therefore not much use for this application. The high tension leads now appear from under the tank and not out of the right side of the engine, and a suitable rubber grommet was found to plug up the hole in the top of the crankcase.

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. I guess the 4 wires could be added to the existing wiring harness and exit under the tank instead of going up the front of the bike frame, but this is how I did it. The ignition system has not given me any problems whatsoever since the mods were carried out, and all trace of misfiring and poor hot starting disappeared immediately Happy motorcycling. Rowan

Click to enlarge

Coil replacement

Rowan`s article above, with his experience in mounting the coils externally, was used as a start point for this article about coil replacement.

The Adler` coils are mounted inside the right hand engine cover ( see diagram ), 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 about five years ago 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. Rowan had recommended several models 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 coils are 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. A auto electrician also advised that it makes little difference to the coil output if it was wired the other way .

This may have be different for older coils that would be marked with both + and - . In this case connect the power to the + terminal.

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 :-

Click to enlarge

1. Connect the four wires to coils and feed them through the grommet to be used to seal the case.
2. Disconnect the power wire from the backing plate ( terminal 5 in diagram ) and connect to the two 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.
3. Connect the remaining two 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 ).
4. 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 .

Don Littleford Jan 07

• T section of dowel to measure depth of piston ( depth indicator with handle ) .
  Leg that goes into the plug hole being approximately 70mm.
• Timing disc socket made out of plastic protractor glued to 14mm socket
  ( you don`t have to remove the 14mm 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.

Procedure :-

Remove spark plugs from both cylinders .

Adjust contact points gap for each cylinder . ( 0.3 - 0.4 mm ) .

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 , parts ,1 & 2 ) .

Put the timing disc socket onto the bolt head and take a degree measurement against the pointer. Record this degree `A` .

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 .

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 .

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 .

The left cylinder is now timed .

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 2 . Undo screws A and B and adjust with cam screw C .

The motor should be run and the timing rechecked .

Depending on the condition and wear in the motor , the timing should not have changed .

	Drill a small hole in the outer ring of the air cleaner ( indicated by arrow ). 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 ).
	Drill out the 4 spot welds which hold the outer ring to the air cleaner body. Photo 4 shows that the drill holes go through the air adjusting vents.
	Remove the filter meshes using a hook wire puller.
	Remove the seal which may have to be replaced if damaged.
	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 inner ring removed showing the air adjusting vents which can be removed. The vents were held in place by the 4 spot welds which have been drilled out.
	A new lever is made from 1 mm brass and silver soldered over the top of broken lever.
	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.
	Adjust the diameter of the outer ring to fit over the air cleaner body, solder together at the cut ( photo 5 ) 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.

PLUG READING - a bit more technical than we thought.

The following article is written as part of a series relating to converting a Yamaha 2-stroke twin road bike into a racer, and is slanted toward 2 strokes. Two strokes, particularly highly tuned ones are very susceptible to engine damage due to ignition and/or carb tuning being incorrect. However, the vast majority of the information, holds true for any internal combustion motor that uses spark plugs though

Taken from `FROM THE PIT WALL` by Jim Reed (Motorcycle Shopper Magazine 1994-1995).

Sports bikes are generally well sorted out as they come from the factory and require very little, if any, tuning to obtain maximum performance on the road. The road racing motorcycle, the 2-stroke in particular, is another matter entirely. A bike that is capable of hurtling around Daytona at speeds in excess of 250 ft/sec must be tuned to the very edge of its capabilities. Go too far, and you have an expensive pile of rubble, or worse an injured rider. Not far enough and you are second.

The tuners who are able to make bikes perform at this level have a number of abilities they share in common. One of these is the skill to `read` spark plugs. I first learned about plug reading at Indy in 1967. Repeatedly, I noticed mechanics, plug in hand, carefully viewing it with some kind of flashlight. Finally my curiosity got the best of me and I asked one of the Champion technicians what was going on. What follows is the gist of what he told me.

Before trying your hand at this esoteric art, you must obtain a plug viewer. Champion makes the best and only readily available unit on the market. Most any racer supply company can connect you with one or you can just contact Champion. I got mine from my Snap-on tool man. Do not use one of those magnifying viewers available from Sears, K-mart etc as they are not designed for the job and, as such, make accurate reading impossible.

When I get around to this topic with my advanced motorcycle mechanics students every year, invariably, some individual informs me they already know how to read plugs. After all its easy, " You simply look for a light brown or dove grey colour on the centre electrode and everything is Ok, right" Wrong.

First, plug colour can only tell you about the generalities of engine condition and performance. Furthermore, colour only accumulates after considerable running time. To obtain specific information about fuel systems and ignition system operation and how they affect engine efficiency, you must look beyond colour as an indicator. By the way, colouration is the result of oil, lead and manganese deposit buildups over time. Lead tends to produce a yellow-brown tint, with manganese assuming a more reddish colour. Also note that at sustained high speed the lead deposits can become conductive and cause high speed misfires. As such, when you are going to do a plug reading, fresh clean plugs are essential.

With your new plugs installed and your viewer ready, fire your bike up and bring it to operating temperature. Assuming you have chosen a suitable venue, perform a top gear, full throttle pass for as long as possible. At the end of the pass, kill the engine and pull in the clutch making sure the throttle is still wide open with the engine is shut off. Never allow the engine to operate at partial throttle. If you do, you`ve just blown your reading.

With the plugs removed, check for correct heat range first. The correct range will allow the plug to run hot enough to keep the insulator nose clean, while not allowing serious centre and ground electrode erosion to occur. If you really miss the mark on the hot side, the nose of the plug will overheat and start to glow red to white hot. Pre-ignition follows which quickly results in a nice round hole being blown through the centre of the piston. If you use the plugs as recommended by the engine manufacturer, this problem is a rare occurrence. So be sure not to skip heat ranges, settle on one brand and stick with it. Consistency of results cannot be achieved by constantly changing brands and types of plugs. All modern racing plugs are good so don`t be tempted to waste time trying to find that `super` plug. OK you`ve for the heat range down, so what`s next.

During your heat range search, you may have noticed some indications of plug overheating. If these indications were shown primarily on the centre electrode, you have too much ignition timing advance. Back the timing down (retard) 2 degrees at a time until a film of soot begins to form on the centre electrode (not on the porcelain but on the wire itself). Continue until the deposit works its way out to within a few thousands of the tip. At this point you should have the ignition timing spot on. On some plugs, this is extremely hard to see. Another indicator of correct timing is that the sharp edge of the end of the centre electrode will show just the faintest amount of rounding beginning to occur. Once the timing is correctly set, run the bike for a few more minutes and recheck the heat range. If it needs adjustment, which is unlikely, go through the timing check procedure one more time.

Always get your timing right before you begin making any carb adjustments. Too much advance is the major cause of detonation. Any leaning of the fuel-air mixture only makes the problem worse, as the correct mixture ratio for maximum power is just this side of the point where detonation begins to occur.

Carb adjustment can now begin in earnest. Note that we are concerning ourselves only with main jet operation. Idle and mid-range adjustments will be taken up another time. Install new plugs and do another high speed pass observing the rules set down earlier. Also, I neglected to mention that it is good practice to install another set of plugs in the plug holes while you are examining those that were in the engine. Over rapid cooling of the cylinder/s may occur on a hot engine resulting in damage, plus open spark plug holes just seem to have a substantial attractive force for errant objects, much as open inlet ports do.

Now, with your viewer look deep into the plug paying particular attention to the area where the insulator meets the plug body. If the mixture is correct, a very slight trace of black soot will be visible. This ring should be no more than 1mm of so wide. IF it is, you are too rich and not producing maximum power. On an air cooled engine the extra fuel is an advantage as it assists in engine cooling. If little or no ring is visible, you are headed for trouble as the engine is running too lean. Heavy detonation, the kind you hear, results in extreme erosion around the perimeter of the piston often accompanied by signs of pre-ignition and piston seizure. The condition of the engine should be checked immediately especially if the engine is a two stroke.

If you are having trouble reading the Spark Plug , contact your local plug supplier and discuss the test with them.
The large Companies can assist by cutting your plug open and doing a report for you.

Be very careful however when you do the plug chop as it is not too easy to:-
Turn off the ignition at full speed .
Keep the throttle fully opened .
Pull the clutch in and coast to a stop.
It needs to be practiced.