Z900 A4 Strange gearbox issue, anyone help?

[Gray17]

Hi Guys, i am in the process of restoring a Z900 A4 american import so probably a KZ900. Circa 1975.
The full bike has been dissasembled, restored and rebuilt, the engine has also been fully stripped and vapour blasted and fully re assembled by myself, with new parts as needed.
Now im at the stage of preparing to run the engine since the rebuild,
I connected up the battery, turned on ignition got the oil light but no Neutral light. Yet bike is in neutral? Ie select fully down one then half up into neutral.
According to the side case logo gears are one down, then N, then 4 up, these all select as they should. However if i go into 5th (fully up) then press on down i get another Neutral and the Neutral lights up. Im guessing this is a false neutral even though rear wheel fully freewheels?
Have i re assembled it incorrectly? I did follow workshop manual to the letter (least i thought so)on re assembly and tried all gears which seem to work ok.
Any ideas whats wrong? And how do i now correct it?
Thanks

[wilsonsjw11]

Where is the striker on the change drum when in neutral between 1st and 2nd gear, is it touching the little plunger on the neutral switch?
If you remove the neutral switch from the transmission cover with neutral selected and look into the hole you should seen the indent on the change drum if its fitted correctly.
Regards
Steve.

[warren3200gt]

If as you say neutral is between where 4th and 5th should be it sounds as if your input is rotating the shaft in the opposite direction to how it should.
If the engine is on the bench is the gear shift lever pointing forwards or backwards?

[zed1015]

It's impossible to get the the selector drum etc wrong.
It sound's like your 5th is actually really 1st and you have the gear lever on backwards or rearset linkage reversed if fitted..
The lever should point forwards.

[Gray17]

Thanks for reply Guys.
Engine now fully fitted into frame
No rearsets fitted and gear lever pointing forward
There seems to be 2 perfect neutrals between 1st and 2nd where it should be (no neutral light) and again between 4th and 5th (lamp lit) in both cases rear wheel spins freely with no noises as though trying to mesh which you usually get with false neutrals.
When stripped gears looked to be in near mint condition with no apparent wear or nicks.
It was checked on bench and all gears selected as they should, couldnt test neutral light though as no power.
Whats strange is both Neutrals select every time easily, what i dont know is if 5th is 5th and not actually 1st as havnt got engine running to try it as yet.
I will try Steves suggestion and remove Neutral switch to check indent on change drum. Do i need to drain oil first?
Thanks

[warren3200gt]

The oil in the sight glass is lower than the neutral switch so no you shouldn't need to drain. If concerned just lean the bike over to the right hand side.

[CAT3]

When you are changing gears, is the engine running or are you just turning the rear wheel to aid gear selection ?

I was under the impression to select 2nd, 3rd, 4th & 5th gears the engine needs to be running so that it spins the gearbox shaft with the blocker ball bearings in. Or did the US version of the 900 not have this feature ?

[Gray17]

Hi, As stated engine not running, not at the stage to start as yet as few wiring issues, but thats diff issue!
I also read posts regarding the un selection of gears if engine not running, no idea if thats unique to UK/Euro models,or not present on US/Canada versions all i can say if i select 1st gear, then move rear wheel slightly back and forth i can select all gears up to 5th. If i dont rock rear wheel can only select 1st or N, ie wont go into 2nd. But think thats true on most bikes as bike not running gears not spinning to mesh.
Thanks
Doesnt explain 2 full Neutrals and light lit on wrong one?

[zed1015]

ALL Z1 through to Z1100 aircooled fours have the positive neutral finder no matter what year or country.
Sounds like the lockout bearings have been taken out as they need centrifugal force to release them all and just rocking the wheel shouldn't be enough to get 2nd and above.
As for the neutral light.
In the earlier engines the selector plate has a hump that contacts and earths the neutral switch in neutral and in any other position the selector plate is flat and runs clear of the switch so unless the plate has been subsantially distorted you shouldn't get the light in more than one position.

[Gray17]

As Steve suggested tipped over to right slightly, took side case off and removed Neutral switch.
First tested switch which works fine.
Next looked through switch hole with torch. Between 1st and 2nd position no raised dimple in Neutral position, however between 4th to 5th Neutral position you can see the raise dimple.
In both cases Neutrals are free spinning at rear wheel and easily selected not like a normal false Neutral?
Anyway, tumbler selects gears and rotates as it should, so question is
Whats going on have i re assembled in incorrectly? More importantly how do i correct it, can it be done in the frame or has whole engine got to be removed? Any other suggestions welcome?
Thanks

[gray]

If memory serves, the round plate in the end of the selector drum ( the one with the raised dimple which triggers the neutral switch) sits on top of 5 or 6 posts, and is held on by a crosshead screw ( I think). If it has been put on in the wrong place, 4 posts further on, you will get the symptoms you have found ( but it shouldn't be possible to put it on wrong as 1 post is longer)
Lean the bike over to the R , take off the gear-lever, footage then sprocket cover. Remove the sprocket then the alloy plate behind it to get access to the gear pawls, and end of selector drum, remove the end and see if it fits better 3 pins round . then your indicated neutral will match actual neutral

[warren3200gt]

Parts 18 & 19, only 2mm difference in length.

Screenshot_20240223_174154_Samsung Internet.jpg (50.21 KiB) Viewed 390 times

[Gray17]

Mmm! That makes sense i will give it a try tomorrow.
Thinking I've probably put plate on wrong hence why i now get 2 Neutrals, never mind the lamp not lighting when it should.
I have tilted bike over with bit of 1" x 2" under 1 side of centre foot will this be enough to remove selector plate cover, or do i 1st need to drain the oil?
Feeling a bit of a nunce now!
Many thanks Guys

[BAFF1960]

Ah! we all feel a nunce at some point but usually in the privacy of our own garage or having a chat in the pub - bloody internet!

[zed9]

Just taken photo of my Z9 A4 in neutral as engine is in bits on bench