ETZ 250 - cannot select 4th and 5th gears

[costellon]

Hello all.
I have recently completely rebuilt an old ETZ 250 engine (got it as a non runner). I swapped a crankcase off another scrapper as the original one was damaged and in my inexperience I did not use a matching pair. I replaced all bearings, very carefully put it together and it starts and runs lovely - except I only have 3 gears ! After 3rd there's nothing .... no clunking or rattling - just a false neutral ... I presume that I have to split it again but my visual inspection of the gearbox before assembly didn't reveal any serious wear ... any ideas ?
Thanks.

[DAVID THOMPSON]

bent shift fork or for some reason the drum is not turning proper
some of the parts may not be in time with the shift forks
or shift does not line up because of the case change

but your eye is not seeing the miss match
gear boxes can be a real hoot!

and the east german guys seem to do thing a bit different than the west
till 1995 and after

i see a lot of little stuff thats odd in mz
that i never saw in VW and BMW over the years

dave

[costellon]

Thanks Dave, looks like i'll have to strip it again - luckily I have an entire spare gearbox assembly.
Any advice regarding my ensuring that everything is lined up correctly ?

[DAVID THOMPSON]

i like to make a jig to holds everything in place
put it together in the side of the case that holds it all the best

may have to make a jig for the open side and see how it shifts

may need a helper to turn the input shaft
dave

[owene]

There is a hidden problem in the ETZ gearbox, that's not in the service manual because nobody it's supposed to touch it, but some (idiots) do: the little "star" on the left side of the gear selector drum, under the washer. It sets the exact angle for each speed. It can be placed only two ways(washer removed specially for pictures):

The correct placing is when in Neutral, the gear arrester(Pizza-Schneider) stays on the top on the flat hill(it's only one hill that is flat on the top)


The wrong placing is the other way.

What happens in the wrong way: finding neutral is easier; 3rd gear is not precise, shaky. 2nd gear will work for a while then suddenly you lose it, like a false neutral.
The shifting pinion of 2nd gear will split


What you can observe that for 4th and 5th gear the positions are the same if the little "star" is placed any position. So your problem is not this, it's just worth checking next time.
It's only one fork that shifts the same shifting pinion: it can be that the fork does not shift the pinion(fork/drum wear problem) or the shifting pinion has split, I don't want to imagine what if both sides engage.

Maybe you already fixed this, I'm curious about the problem.