Dragging gear change - Z1A

[MrDavo]

I assembled the transmission side of my 1974 Z1A project, only to find a gearshift that was refusing to centre and staying at whichever angle you put it.
Clearly something is wrong, and it needs fixing.

The clutch was adjusted and frees off perfectly, and without the transmission cover fitted the gearchange return works absolutely fine. If I just loosen the four cover bolts the gearchange shaft frees up, but that's with the the bolts so loose you couldn't run it like that.

My suspicion was a bent gearchange rod, when I got the bike (in bits) the cover wasn't fitted, and the shaft could have been bent in storage if all the engines weight had ever been put on it. Suspiciously about the only spare part the bike came with was another gear change shaft, so I decided to change it anyway as the splines for the lever were in better condition. Here it is fitted, and all working perfectly. The return spring is the correct 3 turn early one. It is the shorter modified type, so there is no issue with the spring fouling the boss with the dowel. I presume I've got the arms into drum selector right, unless you can see different.



Happy with my work, I put the covers and sprocket etc back on, I checked all was working well before I tightened the cover up, all was fine.
Then I tightened the cover up - and its binding again, no attempt by the lever to return to centre if you push it up or down. Bugger!

The bosses on the inside of the mission cover are pefect, so its not going crooked when tightening up. I have backed off the clutch adjuster, so the cover isn't being tightened against the clutch pushrod. There's not that many things it could now possibly be. I'm wondering whether to replace the three oil seals the gearchange shaft goes through in case they have turned to stone over time and are causing the drag, but I'm not hopeful - they would drag just as much before the cover is tightened. Also, it can't be a sideways endfloat issue causing binding, as the shaft is free to slide as far as it wants in and out of the cover inside those oil seals.

I'm assuming the parts in my bike aren't that unique, so someone is hopefully reading this thinking 'been there, done that!' I hope so, it has me stumped at the moment.

[zed1015]

Some early trans covers fouled the selector mechanism causing the issue you have.
There was a service bulletin on modifying the cover and they changed the design on the later bikes.
Maybe you have one of those early covers .
The mod was simple clearancing job of the casting boss on the inside of the cover that stops end float of the selector fork shaft.
It's diameter was too large so needs some material removing from the side closest to the gear lever return spring.
You should be able to see where the fork has been rubbing if this is the problem.

[Philippe]

Hi Mr Davo

as zed1015 stated before, the problem is possibly due to the casting boss on the inside of the cover, so do as he says.
If I were you I would change the oil seals and certainly the one in the cover...it's a lot less work now that the cover is off then when all is assembled and the oil leaks out...because of an old oil seal .
GrtZ
Philippe

[MrDavo]

Thanks for the feedback. My engine number is later than when they changed that boss, and there are no witness marks at all. Also I do have the modified shorter 3 coil spring, not the early longer one that fouled. What makes me think it must be an alignment issue is the fact that everything is 100% perfect until those last few turns on the bolts that secure the transmission outer cover. If the gearchange was fouling inside its cover then it would happen all the time, not just on final tightening of the outer cover.

I think the shaft HAS to be bent or else there is a problem with the cover, but that has been used, and there is no damage or wear. Also the cover locates on a couple of dowels on the crankcase so no misalignment is possible. Ok I'd have 2 bent shafts, but that part is quite vulnerable when the engine is out and the transmission cover is taken off, which it soon is to disconnect the clutch cable. After that point if the engine is moved around like that, a heck of a lot of side load can be put on that shaft without really realising it.

Looking back at my rebuild thread, here is the engine going in, and the shaft is totally unsupported by the transmission cover, as it had been since we brought it home from Essex in a van. The cover was wrapped up and put away to save it from scratches, in the meantime that shaft was always vulnerable to getting bent.



That photo was posted last August, so we've come on a bit since then (!).

My philosophy, wherever possible, is 'do it once and do it properly'. To that end I have bitten the bullet and ordered from Z Power the 3 oil seals and a new gearchange shaft. PMC still make them (£££), as long as we keep beggaring up the splines on the shafts there will be a demand. If it doesn't fix the problem there will be a great wailing and gnashing of teeth, but if you eliminate all the possibilities the solution should be there.

[MrDavo]

Right this is driving me bloody nuts. The job is stopped until the issue gets sorted out.

As I see it, the problem can only lie in the gearchange mechanism or the cover, there literally aren't any other parts for it to be.

I have fitted a new gearchange spindle with the selector mechanism, and checked that the fouling as per the two service bulletins isn't the issue. I have the 3 spring coil with the shorter 'legs' that don't foul the centre boss, and until the outer cover is fully tightened, everything is working just fine. The cover looks fine, but is a Z1B one, according to John Brookes' book. If it made a difference I'm certain that someone would have documented it, so I'm assuming all covers (z1 to Z900) are interchangeable, except for chain oiler issues. please tell me if I'm wrong.

The cover has no damage that I can see, and all 4 mounting points still have the original miiled finish, so one isn't shorter. Locating the 4 mounting dowels is a faff, but possible, maybe it should be easier. If the cover (or the posts with the locating holes) was bent at all I shouldn't be able to locate all 4 dowels at all, you'd think. getting the 4 bolts in place and tightened isn't a problem.

However, after I cleaned up the hole with wet and dry, put in new oil seals, greased the shaft, and all was well until I tightened up the rear lower mounting bolt, then the same problem, the gear lever suddenly doesn't want to centre any more. Something is slightly on the p!$$ somewhere, and once the cover is tightened we have binding against the shaft where it passes through the cover. I can't leave the cover less tight, or use spacers / washers to change the alignment as then I would probably have clutch adjustment issues.

The new PMC gear selector rod was anodised black. A carp out of focus photo I know, but, where the gear rod crosses the frame tube, you can see a witness mark which corresponds to the hole thorough the alloy casing. I wondered about just getting this hole drilled oversize, but then you have support issues, and could bend or damage the inadequately supported gearchange when using it.



This has to be sorted. Although I can't see what's wrong, I eliminated the shaft by replacing it with a new one, now I need to try another cover.
DK have an OK one for sale (it will be a challenge to match the professionally polished finish of the existing cover) but off a later bike than mine. Firstly, does that matter? Secondly, before I take the plunge, can anyone loan me a Z1 transmission cover to try first? It can be in any state as long as its all there, and preferably in the Greater Manchester region so I can pop by to pick up and return it, but I'll go farther afield if necessary, or pay any necessary postage.

[z1bman]

have you tried it without the dowels ?

[MrDavo]

No, but see below.

I got a pm from Trev in Rochdale (aka Ogre) kindly offering to lend or sell me a spare cover, off a Z1B we think. I jumped on my CL450 and nipped up there to pick it up. Fitting his cover produced exactly the same result so at least I’ve ruled out the cover without spending £75 or so to find out.

When I described the problem, where tightening the lower rear cover bolt made the gearshift bind, Trev suggested packing that corner with a washer over the locating dowel. I said I’d not tried that, as it certainly shouldn’t work, also I had been nervous about the clutch adjustment if the cover wasn’t square.

Having apparently ruled out everything but still having the problem I felt I had nothing to lose, so I popped a small spring washer over the dowel on the crankcase, so it sits between case and cover, and tried again. All four bolts tight, and the gearshift is free and centering!

It shouldn’t work, but it does, I may never know why. I’m wondering if a locating dowel might be slightly out of round or something, it’s in such an awkward spot to properly check. It’s definitely the sort of thing that you should sort out before you put the engine in, not after.

As I got sick of reassembling everything including the sprocket tab washer etc I now need to try everything back in place and nipped up, while hoping my miracle solution continues to work.

Many thanks again to Ogre, and other members who have been in touch. I’ll keep you posted, once this nightmare is finished I can get back to reassembly of the Z1A.

[kev edwards]

Could you try it without that particular dowel in it?