Plunger gearbox reassembly

[owain]

So I fitted a new gearbox mainshaft to my A10 plunger a few weeks ago. I did as recommended to prevent damage to the clutch oil seal: bolt on the empty gearbox housing and carefully insert the gearbox mainshaft through the oil seal. It went pretty well!
(I should add that when I removed the old gearbox mainshaft, I simply left all the other internals in place and just slid the mainshaft out and replaced with a new one.)

The issue that I am now having is that my once perfectly working gearbox has become a poorly selecting lump of metal that seems to seize completely. I've taken on and off the outer and inner cover half a dozen times now without any luck. I'm using hylomer instead of gaskets as that is what I used last time and it worked well. The gears seems to select ok when I push the camplate around with the inner and outer covers off. I have the layshaft thrust washer between the last sprocket and the layshaft bush that sits in the inner cover. The gears and camplate are in neutral when I'm assembling and the gear selector fork is making good contact with armature that moves the camplate. I cannot see where I am going wrong with this? 

As a reminder the selection is 1 down 3 up isn't it? I must be losing my mind at this point haha

[muskrat]

G'day owain.
1 up 3 down.
Try a paper gasket between case and inner cover.It can be a bit finiky there.
Cheers

[chaterlea25]

HI All
Owain, another possibility is that one of the gears slipped out of the selector fork(s)
If you can remove the inspection cover on the back of the box you should be able to see whats happened

John

[owain]

unfortunately there is no inspection cover on the plunger gearbox. The gears seem to select properly with the inner and outer covers off. I've got a fancy camera that I use to have a look none the less though!

I saw on some previous posts that GreyBeard mentioned that the gearbox is very sensitive the smallest positioning of the gears. Such a pain as I'm having to remove and replace gasket sealer and lock washers over and over again.

[JulianS]

Owain, you say;

"I have the layshaft thrust washer between the last sprocket and the layshaft bush that sits in the inner cover"

That thrust washer should be the other side of the first gear pinion, between the pinion and the layshaft shoulder, chamfer towards the layshaft shoulder.

Photo is from a swinging arm box but the thrust washer position, indicated by the arrow, is the same for both plunger and swinging arm.

[owain]

Thanks Julian! You may have just fixed it. My thrust washer is on the outer most side of the pinion. It's hard to tell where the thrust washer should go according to the parts diagram. I'll inspect that the forks are engaged properly and will move the thrust washer to the position shown in your picture and hopefully that should resolve it!

...as soon as the postman arrives with the new lockwashers that is!

[Greybeard]

I saw on some previous posts that GreyBeard mentioned that the gearbox is very sensitive the smallest positioning of the gears.

Well that was my experience. I don't know if they are always that sensitive. If I remember correctly, I removed the inner gasket to cure the problem.

[owain]

Update: It seems that Julian had it right. Checked that the forks were engaged (they were) and moved the washer onto the correct side of the pinion. Went back together easily and can finally ride my A10 again 

[Greybeard]

Update: It seems that Julian had it right. Checked that the forks were engaged (they were) and moved the washer onto the correct side of the pinion. Went back together easily and can finally ride my A10 again 

Great news! 👍

[Minto]

Awesome stuff!
Well done all involved.👍