Incorrect adjustment of the neutral selector can cause gears to jump out of the selected position. Many owners spend a lot of time investigating the neutral selector when the cause of jumping gears lies elsewhere. While jumping fourth gear is common, it is not common for the other gears to jump out of their selected positions into the adjacent neutral point. If this happens, double check the oil level in the gearbox. If the problem persists, disconnect the neutral finder completely, then drive the car to see if the defect has been eliminated.

The workshop manual does not cover setting of the neutral selector in any detail. Although, surprisingly, it is covered quite well in the Owners manual. A Sachs technical bulletin is available on our website giving their version from the early days of Messerschmitts. Located behind the clutch drum, it is a very simple lever system made out of pressed and riveted components. With the selector quadrant and detent arm finally assembled, you might like to check the movement and clearance position of the neutral finder IN EACH OF THE GEARS. There is good reason to take extra care in the setting of this device. To identify the travel of the operating arm, I made up a brazing rod neutral finder cable that I could use to operate the mechanism, and carefully measured the distance between the inner boss of the cable mount on the crankcase and the end of the cable carrier on the neutral finder

To complete the measurements, I used a vernier calliper, and the arrangement is shown in diagram 3. Firstly, I found the contact position of the neutral finder cam with the neutral finder quadrant and measured the distance between the two points for each of the gear positions 1st trough 4th. Next, I measured the distance between the same two reference points once the quadrant had ‘just’ been knocked back into neutral by pulling on my brass rod. I noticed that the clearance positions of my neutral finder varied by about 2mm, and the ‘knock back’ positions by about 1 mm more. (And my components didn’t appear to be worn!)

Although these variations in movement seem very small, let me remind you that, particularly in 4th even slight movement of the neutral finder arm, once contact with its cam has been made, will force the selector quadrant out of it’s full detent position. That starts to disengage the dog clutch! That 1 mm you have questioned is more than enough to move the 4th gear dog clutch half out of engagement. (This may well be one of the reasons for wear on the dog clutches and premature jumping out of gear)! I think that the total cable movement I can get with my neutral finder trigger on the gear lever is 11mm! and 2mm in 11mm is almost 20%! The message I wish to impart is that adjustment of the neutral finder cable is sensitive, AND CRITICAL!

Using this method to set up the trigger mechanism will make it very easy to set when you finally do get the engine back in the car. Couple up the neutral finder cable, and adjustment is really dead easy. You just make the distance between your two reference points, the inner boss on the crankcase and the end of the cable carrier on the neutral finder arm, slightly (say about 1mm) MORE than the MAXIMUM length of the neutral finder clearance distance in any of the gears, and you then KNOW that the Neutral finder mechanism can’t be interfering with the detent mechanism. (Hint, you can always make up a bit of stick the right length and use it during cable adjustment!)

The total variation in the clearance position of my Neutral Finder was about 2mm. If the variation exceeds 2mm you may find that you need to ‘massage’ the finder cam slightly to get the finder to work in all gears. I have not had to do that, but the design of pressed and riveted construction cannot be particularly accurate. It may be a further potential original cause of gear jumping if these distances vary wildly, causing the neutral finder to force the detents out of full engagement in some gears, when apparently properly adjusted in others. If you need to do this – be careful – the geometry has a high mechanical gain, and a little metal removed will have a lot of clearance effect.

Good lubrication is vital part in preventing gearbox wear. If the clutch inspection cover is used as the oil level, you can be certain that there will always be sufficient oil. Oil should start to run out of the cover when it is removed on level ground and normally about 800ml of SAE 90 gear oil is required for a complete oil change. If the oil level is too low, the first clue is often jumping gears. If you have a worn gearbox, things can be improved by using a SAE 140 oil and I have also had good results from 85W140 multigrade oil from Wal-Mart stores in the USA. There are many oils available today that are marketed for use with limited slip differentials. Many of these have ‘clutch’ plates similar to the Sachs design. These higher viscosity oils are often used in agricultural applications and you should try your nearest tractor dealer in case of difficulty. However, it is essential that these gearbox lubricants are compatible with friction clutches running in oil and you are usually safe with oils marked for limited slip differential use. Lubricants marked as EP or Hypoid that do not mention compatibility with limited slip differentials, will destroy the clutch. If you have a worn and excessively noisy gearbox, try using 140 grade oil that is intended for steering boxes. This works well and I have used it for over 30 years. There is no noticeable difference in operation unless you use your Messerschmitt at very low (freezing) temperatures when it can create some clutch drag during a cold start.

Unfortunately, there were some errors in the engine manual that resulted in use of the level plug on the clutch housing to determine the oil level. This level may have been acceptable when used in motorcycle applications where the engine has less weight to pull and less heat from the clutch operation. Do not touch this level screw! It normally strips when removed and you will have to remove the entire clutch housing to repair it.

In the KR200, the clutch housing and primary chain operates as an oil pump to feed oil back into the gears through an ingeniously designed duct system. Oil is picked up by the chain and thrown off by centrifugal force into the gearbox feed duct. This can only work effectively if there is enough oil in the gearbox. Check the parts manual and make sure your engine has the oil thrower ring and diverter casting in position. This is often damaged when the primary chain is badly worn and makes contact with the aluminium diverter casting. Some previous owner may have left this part off following an overhaul. It does not affect the operation of the gearbox but does limit the effectiveness of the lubrication.

Take great care if there is a strong smell of fuel in the gear oil. In this case it is possible that a leak has developed from the crankcase area. Normally this is accompanied by a very smoky exhaust but should be treated with caution as the gear oil becomes diluted with fuel reducing the lubricating properties. If in doubt, change the oil and check again later.

You will have noticed some wear on the six holes in the double sliding gear that are entered by the pins on the corresponding fourth gear wheel . The Partsmart #1807 engine manual compiled by Robert Soditus covers treatment of this defect. The design of the selector mechanism does not allow much compensation for wear in the respective gear drive dogs. If any of the gears are running on the edge of the drive dog, instead of being fully engaged, then the affected gear will be more susceptible to jumping out of mesh. Adjustment and wear compensation for the selector system was fully discussed in the August 2003 edition of Kabinews. This article is now available on our website.

Good lubrication is vital part in preventing gearbox wear. If the clutch inspection cover is used as the oil level, you can be certain that there will always be sufficient oil. Oil should start to run out of the cover when it is removed on level ground and normally about 800ml of SAE 90 gear oil is required for a complete oil change. If the oil level is too low, the first clue is often jumping gears. If you have a worn gearbox, things can be improved by using a SAE 140 oil and I have also had good results from 85W140 multigrade oil from Wal-Mart stores in the USA. There are many oils available today that are marketed for use with limited slip differentials. Many of these have ‘clutch’ plates similar to the Sachs design. These higher viscosity oils are often used in agricultural applications and you should try your nearest tractor dealer in case of difficulty. However, it is essential that these gearbox lubricants are compatible with friction clutches running in oil and you are usually safe with oils marked for limited slip differential use. Lubricants marked as EP or Hypoid that do not mention compatibility with limited slip differentials, will destroy the clutch.

Unfortunately, there were some errors in the engine manual that resulted in use of the level plug on the clutch housing to determine the oil level. This level may have been acceptable when used in motorcycle applications where the engine has less weight to pull and less heat from the clutch operation. Do not touch this level screw! It normally strips when removed and you will have to remove the entire clutch housing to repair it.

In the KR200, the clutch housing and primary chain operates as an oil pump to feed oil back into the gears through an ingeniously designed duct system. Oil is picked up by the chain and thrown off by centrifugal force into the gearbox feed duct. This can only work effectively if there is enough oil in the gearbox. Check the parts manual and make sure your engine has the oil thrower ring and diverter casting in position. This is often damaged when the primary chain is badly worn and makes contact with the aluminium diverter casting. Some previous owner may have left this part off following an overhaul. It does not affect the operation of the gearbox but does limit the effectiveness of the lubrication.

Take great care if there is a strong smell of fuel in the gear oil. In this case it is possible that a leak has developed from the crankcase area. Normally this is accompanied by a very smoky exhaust but should be treated with caution as the gear oil becomes diluted with fuel reducing the lubricating properties. If in doubt, change the oil and check again later.

You will have noticed some wear on the six holes in the double sliding gear that are entered by the pins on the corresponding fourth gear wheel . The Partsmart #1807 engine manual compiled by Robert Soditus covers treatment of this defect. The design of the selector mechanism does not allow much compensation for wear in the respective gear drive dogs. If any of the gears are running on the edge of the drive dog, instead of being fully engaged, then the affected gear will be more susceptible to jumping out of mesh. Adjustment and wear compensation for the selector system was fully discussed in the August 2003 edition of Kabinews. This article is now available on our website.

Once dismantled (with the aid of a 2lb engineering hammer!) and inspected, it turned out to be a can of worms. Some bits were wonderful, nearly new in fact. Others were simply destined for the dustbin. Crank, barrel, main bearings and dynastart were mint and perfect.

It had a nice new layshaft with perfect 1st gear and completely unworn dog clutches, the 1st and 4th constant mesh gears were really good (unworn), but the 2nd and 3rd gear fixed and sliding gears were a bit worn, but didn’t look too bad. The clutch plates and primary chain were consigned directly to the dustbin (from where I had to rescue one plate to make a clutch centre locking tool).

After completely dismantling the engine, all the gearbox parts and the engine casings should be thoroughly cleaned. This should reveal evidence of wear at the various contact points for the gears and dog clutch. I am not sure that I agree with all of the notes in the manual in this area, particularly the part about the shims (171) under the neutral selector! detent arm (170). My feeling here is that you should shim the detent arm first to ensure that you get the selector fork/quadrant (166) to give full engagement of both the 1st and 4th gear dog clutches (on gears 139 and 142) when the gearbox is assembled. If the engine has been operated with too few or too many shims fitted you will find a polish mark on either the face of the 1st constant mesh gear (139) or the sliding gear (138) where the quadrant has tried to force the flat faces of the one of the constant mesh and sliding gears into contact. Since the Quadrant has a fixed total sliding gear movement, you need to ensure that this is central and engages the dog clutches on these two constant mesh gears equally at the ends of its travel. I suspect that this is one of the primary causes of gearboxes jumping out of 1st or 4th with resultant 139 wear to the 138 dog clutches.

This adjustment is particularly important for top gear where the angle of the selector fork is large. A small movement in the arm can change the mesh of the 4th gear dogs significantly. This is one of the reasons why the end float on the shafts, particularly the output shaft, is important.

One trick seems to be to shim the output shaft to adjust the whole process further to aid centralisation of the whole assembly. I had excessive end float, about .O15 inch (0.4mm) too much. I was able to position the output shaft shims to help the engagement of the 4th gear dog clutches in relation to the end movement position of the sliding gear. These are the most important consideration in avoiding jumping out of 4th gear. Ideally, I would prefer to add see polish marks on BOTH the 1st here to constant mesh gear AND the 3rd gear correct face of the sliding gear!)

After cleaning, assemble all of the selector fork, detent and gears with the rollers in the timing side of the crankcase. Then check the 1st and 4th gear clearances between the sliding gear and the constant mesh gears. You may need to make a “keeper plate” to hold the drive side shaft end at the appropriate centre to do this, but it will also allow you to see how sensitive the 4th gear mesh is to movement in the quadrant and it’s position. Refer to the diagram for details of how to add and subtract shims for the correct adjustment.

I believe this is the primary adjustment to the gearbox, if you can’t get the core 1st and 4th gear dog clutch engagement right, I would suggest that the rest is doomed! It should be done before completing any other assembly work. This is also a completely different way of looking at the eccentric shims under the neutral finder! detent arm assembly. I think that building gearboxes starts with alignment of gear/dog clutch mesh, not with getting the selector assembly to centre. Eccentric shims are available from MOC partsmart.

Jumping out of gear can be caused by 4 different conditions:

1. Improper shifting
2. Neutral select cable mis-adjustment
3. Worn gears
4. Shaft end-play

Each of these items will be discussed but first we should understand how the transmission operates. The shifting lever on the transmission operates a ratchet that positions the gears for different speeds. The engine drives the layshaft which has a 1st and 4th gear at each end that is firmly connected to the layshaft.

In the centre are 2 separate sliding gears (2nd & 3rd gear) that are driven by the layshaft when they are positioned over lugs on the layshaft. The output shaft is ‘splined’ and has a sliding cluster gear which is continually meshed with the sliding gears on the layshaft. All these sliding gears are moved laterally as a group when the transmission is shifted. There are holes in the side of the sliding cluster gear that ‘lock onto’ lugs of the end gears of the output shaft when in 1st and 3rd gear.

First Gear
The gears are shown in the 1st or low gear position. Gear 1 is a machined part of the layshaft. It meshes with gear 2 which is free to rotate on the output shaft. Gears 2and 3 are ‘locked’ together by lugs on gear 2. Gear 3 turns the ‘splined’ output shaft.

Getting into gear
A shaft from the shifting arm connects to the ratchet assembly. The top of the ratchet assembly moves the selector fork to the different gear positions and the pawl holds the fork in place. The neutral selector is used to force the pawl out of the selector fork and allow the gears to go to a neutral position. An inexpensive new pawl spring will help hold the pawl in the selector fork notch. Using a stronger spring is not necessary and would only make it harder to shift gears.

The sliding gears for 2nd and 3rd gear have been positioned over the dogs on the layshaft by the selector fork. If spacers have been added or removed under the layshaft 1st gear, it may be necessary to add or remove eccentric washers at the neutral selector assembly to get the proper clearances between the loose sliding gears and the dogs on the layshaft when in neutral. When the gears are positioned in 4th gear, the sliding cluster gear is positioned by the selector fork and should lock-in to the 4th driveshaft gear as much as possible.
The sliding cluster gear should not be touching the 4th layshaft gear.
The overall layshaft distance should should be less than the space between the crankcase halveswhen everything is bolted together with the proper thickness crankcase gasket.

If there is any ‘binding’ of the layshaft, it may be necessary to have the layshaft 4th gear pressed further onto the shaft and start all over.

Neutral Selector Adjustment
Neutral selector operation is quite simple. Pulling on the cable rotates the selector and forces the pawl out of the selector fork. It has a return spring. The other spring is only used to keep the cable end captured.

When properly adjusted, with the engine in gear, you will hear a ‘click’ back at the engine when the finger lever is squeezed. You can also check the amount of movement of the finger lever after you hear the click to insure that it is not just on the edge of releasing.

Worn Gears
The sliding gears on the layshaft become worn and are mostly responsible for jumping out of 2nd and 3rd gear problems. The ‘dogs’ on the layshaft fit into the sliding gears and they also become worn. The photos show worn layshaft dogs and a badly worn sliding gear. This wear can cause the sliding gear to move laterally and jump out of gear.

Final Word on Gear Problems
If you have problems with grinding gears when shifting or jumping out of gear, FIX IT NOW! The problem will only get worse until the gears are totally destroyed and it is almost impossible to replace them.

Another problem is getting spacers (washers, shims) for the shafts to get the proper end-play. I have never found a source for these spacers and had to make them by hand which is no easy task. If the shafts have too much end-play, continual lateral vibration can cause the gears to ‘walk’ out of position.

I would also suggest that anyone working on the engine get publications from Partsmart.

These are:
1805 Sachs parts list
1806 KR200 workshop manual
1807 Engine manual

Select first gear, and then turn the crankshaft 31 revolutions. Take out the plug will make it a bit easier. If the mainshaft turns 4 revolutions you have the late, helical first gear with 8/29 teeth. This is normally fitted in all Messerschmitts after mid 1955, and also in all other later dynastarted engines. If the mainshaft makes 4.5 revolutions you have the straight cut first gear with 9/29 teeth.This is normally fitted in all kickstarted engines and also in early 1955 KR200 engines. As far as I can remember I have only found straight cut first gears in 200cc engines with the 20mm crankshaft.

Now select second gear, and turn the crankshaft 20 revolutions. If the mainshaft turns 5 revolutions you have the normal gear with 13/24 teeth. It is fitted in all SACHS engines except 150cc motorcycle engines with engine number under 1343492. If the mainshaft makes 5.5 revolutions you have the very rare high gear with 14/24 teeth. Through the years I have seen several 150cc engines, but that gear I have only seen in handbooks.

Now select third gear, and turn the crankshaft 21 revolutions. If the mainshaft turns 8 revolutions you have the early, high third gear with 17/21 teeth. It is fitted in all SACHS engines up to 1957. Unfortunately, I don?t know if it changed in the beginning, middle or end of 1957. The reason for change was that the teeth on the twin slider gear were too fragile. But there is no reason to worry if you make normal gear shifts, and it gives more sensible steps between the gears than the later version. If the mainshaft turns 7.5 revolutions you have the late, low third gear with 16/21 teeth. It is fitted in all SACHS engines from 1957 and later. As far as I know SACHS only made dynastarted 200cc engines from that time.

Finally select top gear, and turn the crankshaft 11 revolutions. If the mainshaft turns 5.5 revolutions you have the low top gear with 20/19 teeth. It can often be found in scooters and motorcycles. They are fitted in all Nobels and also in late Fram-King-Fulda (Swedish Fuldamobil S7) and also in engines for lift cages in television antennas. If the mainshaft turns 6 revolutions you have the high top gear with 21/18 teeth. It is found in all KR200 engines, and also in dynastarted KR175 engines. I know that the handbook?s figure of the total ratio suggests that it should have the low top gear. But I have four dynastarted KR175 engines at home that can be turn over, and they all have the high top gear. They also have the helical 8/29 teeth first gear, and also that doesn?t agree with the handbooks. Unfortunately I have no kickstarted KR175 engine so I can?t tell the top gear ratio for them. But the mechanism for the kickstart always has straight cut gears, so first gear is definitely 9/29 teeth. The high top gear can also be found in early Fram-King-Fulda and also in 150cc and 175cc motorcycle engines, but only if they have the additional letter G. Swedish graveyard tractors always have high top gears, but I am not sure what the snowmobile Sputnik has.

If you want to make your own calculations of the total ratio you also has to remember that the primary chains sprocket on the crankshaft has 16 teeth and the clutch case has 34 teeth. The KR200 has 13/30 teeth in the final drive chaincase and the figure for KR175 is 16/38.

If you have any comments on this please contact me on three.three@swipnet.se

Anders Johnsson, Sweden