Bernies Bike Shed

NSU ‘Superlux’ engine strip

One of the ‘Adler to Zundapp’ members took part on the Saturday run of the West Kent Run on a very nice restored NSU ‘Superlux’ The rider was a young lad in his late 20’s and the Superlux was restored by his granddad .Unfortunately before many miles had been covered the Lux started to get the gremlins in the gearbox area! first with jumping out of gear between 1st and 2nd gears and then finally seizing up solid, fortunately the speed was low and no harm came to the rider!

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The restored Superlux

It’s now 2017 ,6 months after the Run I asked the owner  was the bike  in a running condition again? only to be told that it wasn’t due to the fact the owner couldn’t find anybody willing to take the engine apart and find the problem.So i offered to have a look The NSU Superlux is a  rather difficult engine in regards to the gearbox to work on.

Now with the engine on my workbench the rear engine sprocket would not turn either way! once the primary drive gear was removed the crank revolved quite easy so no problem there, problem definitely in the gearbox once the seven 11 mm and four 10 mm nuts and 1 countersunk screw was removed the right hand cover comes off.When the cover had moved about 6 mm apart,I notice the rear sprocket could then rotate! which is a good sign, With the cover off  I refered to the parts book , it showed a spacer washer was missing on the layshaft end! although not OK! it shouldn’t cause the box to seize so all  the gears had the be removed and on removing the layshaft bottom gear the source of the gremlins was shown,on the other end of the layshaft,that spacer washer   was also missing and was  trapped against the wall of the gearbox casing it was damaged and been in contact with the bottom gear

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The layshaft spacer washer not where it should be!! When building a gearbox this washer can often get missed

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The washer had taken a bashing now being split and deformed.Now because both washers are missing the gears could move 2 or 3 mm in free play! not good for gear change!

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another source of bad gear selection!! there is a small o mark on the gearchange ratchet 4 teeth above the bronze bushe! that o mark should be level with the bushe hole.

Below are more pics of the gear change parts

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The selector drum with forks .The grub screw ,spring and pointed dowel engage the  4 notches which are the 4 gears .The spring maybe short in length as engagement is very weak which also gives a sloppy gear change.

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The gear change ratchet turns the spur gear on the selector drum.

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When the right hand cover is assembled the ratchet is held in the correct position by this small 10 mm screw and dowel,when all things are in place,the screw is removed.

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On inspection the ratchet showing signs of excessive wear.

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More parts that make up the gear change mechanism.

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The gears on the workbench although looking correct the source of no 3rd and 4th gear selection was the gear with the 2 dogs either side on the layshaft was on the shaft the wrong way round!!!

Although numerous small things that would not help a sweet gear change were found, The gears would not change from 2nd to 3rd and then to forth gear i was a somewhat puzzled The problem was solved when sliding the gears by hand on their shafts! on the layshaft the gear in the picture with the thrust washer just showing between the dogs was stopping the 2 gears engaging because their is no recess for the washer in the gear ! I knew the washer was in the correct place!! so the gear must be the wrong way round ! sure enough when the gear was placed on the shaft the other way round there is a recess for the washer! hooray!!! it also means the selector fork groove is also in the correct position.Happy to say all four gear can be  selected.

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