Gearbox Cover Issues

Eric Bauer · Nov 14, 2022

Hi all -

I removed my outer and inner gearbox covers to replace the gaskets as my box was leaking badly. Luckily someone has already installed an SKF bearing on the layshaft. Is it possible for the layshaft to come out of the bearing race? After pulling the inner cover the layshaft now can move up and down and when I push it back towards the rear of the gearbox where the bearing race is, the kicker gear will not go in far enough to fit the inner cover on. I can't figure out why it won't go back in. It's very close, maybe 3/16 of an inch so it doesn't seem to me it could be completely out of the race. I kind of stuck here. Any help appreciated. Thank you

L.A.B. · Nov 14, 2022

Eric Bauer said:
Luckily someone has already installed an SKF bearing on the layshaft.

It's only lucky if that SKF is an NJ203E roller bearing. An SKF ball bearing could be the original.

Eric Bauer said:
Is it possible for the layshaft to come out of the bearing race?

If it's the aforementioned roller bearing then the inner race would come out with the layshaft. If it's the 6203 ball bearing then the layshaft could come out if the fit is loose enough.

Eric Bauer · Nov 14, 2022

L.A.B. said:
It's only lucky if that SKF is an NJ203E roller bearing. An SKF ball bearing could be the original.

If it's the aforementioned roller bearing then the inner race would come out with the layshaft. If it's the 6203 ball bearing then the layshaft could come out if the fit is loose enough.

Thank you. It says Germany on it so I am pretty confident it is new. If it came out how can I get it back in?

L.A.B. · Nov 14, 2022

Eric Bauer said:
It says Germany on it so I am confident it is new.

Unfortunately, that doesn't answer the question of whether it's a ball or roller bearing.

Eric Bauer said:
If it came out how can I get it back in?

It would help if you could say which type of bearing (ball or roller) it is.

Eric Bauer · Nov 14, 2022

L.A.B. said:
Unfortunately, that doesn't answer the question of whether it's a ball or roller bearing.

It would help if you could say which type of bearing (ball or roller) it is.

I cannot see what it is as the layshaft is blocking it.

L.A.B. · Nov 14, 2022

Eric Bauer said:
I cannot see what it is as the layshaft is blocking it.

That would have been my next question.

I assume that an "SKF" bearing is written in notes or a spares list that you have (so any mention of what type of bearing it is?) because to see the bearing you would have to strip the gearbox to how it's shown in the picture below. (The bearing is the FAG 6203.TB.P63 phenolic cage ball bearing, not the NJ203E roller).

The only thing I can think of that might prevent the layshaft from going fully home is if either the 4th or 3rd gear pairs are not sliding into mesh (mainshaft 3rd not fitted, below).

L.A.B. · Nov 14, 2022

Also, as far as I can remember, it isn't possible to remove the layshaft from the bearing with the gears and selector forks in place.

Eric Bauer · Nov 14, 2022

L.A.B. said:
Also, as far as I can remember, it isn't possible to remove the layshaft from the bearing with the gears and selector forks in place.

Thank you very much - is there a preferable gear to put the box into that might bring those two together?

L.A.B. · Nov 14, 2022

Eric Bauer said:
Thank you very much - is there a preferable gear to put the box into that might bring those two together?

If a gear pair is out of mesh then you could try turning the layshaft, mainshaft and sleeve gear as you push on the layshaft.

MichaelB · Nov 14, 2022

If everything is correct, could be the kicker is not clocked correctly for install.
I prefer to install the kicker in the inner cover, rotate it so the pawl retracts, holding the kicker as a handle, slide the assembly together.
Careful not to rotate the kicker, unloading the pawl..

Eric Bauer · Nov 14, 2022

MichaelB said:
If everything is correct, could be the kicker is not clocked correctly for install.
I prefer to install the kicker in the inner cover, rotate it so the pawl retracts, holding the kicker as a handle, slide the assembly together.
Careful not to rotate the kicker, unloading the pawl..

Appreciate your thoughts. The problem is the kicker gear that goes on the end of the layshaft is sticking out about 3/16". The inner cover is flush so there is no way it could go on that I can see. I have been trying to work the gears (it is in neutral) now but it wont seem to go any closer in.

MichaelB · Nov 14, 2022

Oh, that's a problem..

L.A.B. · Nov 14, 2022

Eric Bauer said:
The problem is the kicker gear that goes on the end of the layshaft is sticking out about 3/16". The inner cover is flush so there is no way it could go on that I can see.

The outer end of the kickstart shaft locates in a recess about that distance.

Are you fitting the kickstart shaft into the inner cover first (with the pawl retracted by the stop plate)? Then fitting the cover with the kickstart shaft and not trying to fit the inner cover with the kickstart shaft on the end of the layshaft because the kickstart pawl possibly wouldn't locate correctly.

Eric Bauer · Nov 14, 2022

L.A.B. said:
The outer end of the kickstart shaft locates in a recess about that distance.

Are you fitting the kickstart shaft into the inner cover first (with the pawl retracted by the stop plate)? Then fitting the cover with the kickstart shaft and not trying to fit the inner cover with the kickstart shaft on the end of the layshaft because the kickstart pawl possibly wouldn't locate correctly.

I never removed the kickstart shaft. The gear itself is outside of the case. I think there must be a meshing issue. I assume if it is in neutral the gears should spin. I had it in first and they would spin, now it is in neutral and they will not.

Eric Bauer · Nov 14, 2022

L.A.B. said:
The outer end of the kickstart shaft locates in a recess about that distance.

Are you fitting the kickstart shaft into the inner cover first (with the pawl retracted by the stop plate)? Then fitting the cover with the kickstart shaft and not trying to fit the inner cover with the kickstart shaft on the end of the layshaft because the kickstart pawl possibly wouldn't locate correctly.

Don’t you think the only option at this point is to start removing gears?

L.A.B. · Nov 14, 2022

Eric Bauer said:
I think there must be a meshing issue. I assume if it is in neutral the gears should spin.

In neutral the individual gears won't all be free to rotate on their shafts, for instance, mainshaft 1st is splined to the shaft, therefore, layshaft 1st also turns with mainshaft 1st but there's no drive to the sleeve gear.

Eric Bauer said:
Don’t you think the only option at this point is to start removing gears?

That was going to be my next suggestion.

Eric Bauer · Nov 14, 2022

L.A.B. said:
In neutral the individual gears won't all be free to rotate on their shafts, for instance, mainshaft 1st is splined to the shaft, therefore, layshaft 1st also turns with mainshaft 1st but there's no drive to the sleeve gear.

That was going to be my next suggestion.

But the shafts should spin freely, correct?

L.A.B. · Nov 14, 2022

Eric Bauer said:
But the shafts should spin freely, correct?

Not exactly because the mainshaft is locked to the crankshaft by the clutch and primary chain (with the lifter mechanism removed, can't be disengaged without stripping the clutch) and the layshaft is geared directly to the sleeve gear (by layshaft '4th') so would be prevented or at least restricted from turning freely by the drive chain and rear wheel.

Eric Bauer · Nov 14, 2022

L.A.B. said:
Not exactly because the mainshaft is locked to the crankshaft by the clutch and primary chain (with the lifter mechanism removed, can't be disengaged without stripping the clutch) and the layshaft is geared directly to the sleeve gear (by layshaft '4th') so would be prevented or at least restricted from turning freely by the drive chain and rear wheel.

I took the forks off and the layshaft came out - some of the rollers had fallen out of the race - I guess upon taking the case off some how? It was really siliconed on there. Either way, the rollers, which had fallen out and were sitting in the middle of the race, were stopping the layshaft from fully seating. I guess I will be putting in a new layshaft bearing now after all.

Schwany · Nov 14, 2022

The JS Motorsports fiberglass reinforced silicon gaskets work well on the gearbox, and are reusable a few times for redo instances like what you are currently experiencing.

Gearbox Cover Issues

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