Gearbox access through the chain case

[Superflash]

Gidday all,

Got one for the Plunger guys.

Has anyone thought about doing what Triumph did with their unit engines, and cut a big hole at the rear of the chain case that is sealed with a circular cover held in with 6 screws? I only ask as I'm currently restoring my '72 650 Bonnie, and the way they've done it, you have full access to the rear of the gearbox in order to remove the final drive sprocket and layshaft blind bush with the engine in the frame.

I was wondering if it was possible to do something similar with the A10 so that you wouldn't need to drop the motor out in order to strip out the gearbox internals.

Their idea of having a hole in the case where the layshaft blind bush is was also a good one. All it took was a light tap with a drift and the bearing just fell out. Easy as..

Cheers

[muskrat]

G'day Tony.
I was just contemplating doing that as well. I'm just putting a proper seal where the felt one was.
Yes a member has done that but he has been missing in action. duTch hasn't been on since Jan 2020.
Search his posts might find a pic or two, 300 pages! https://www.a7a10.net/forum/index.php?topic=4282.msg62295#msg62295 is a post with A65 types.
Cheers

[Greybeard]

How often do we need that access? Is it worth the effort?

When I changed my final drive sprocket and seal I took the head off to make it easier to get the lump out of the frame. While the lid was off I decoked the top end.

[KiwiGF]

Wot, u plunger guys have to take the engine out to replace the final drive sprocket? 

[muskrat]

G'day Kiwi.
Yes  but I can't remember the last time, maybe 30 years ago  I'll be replacing the sprocket & seal even though their in good condition.
Cheers

[Superflash]

I guess given the number of times you would need to replace the drive sprocket / bearings and bushes at the back of the gearbox, it wouldn't make much sense going through the hassle of doing this.

It was really just an idle thought when stripping down the Bonnie motor just how easy it all was.

The pain and aggravation of trying to sort the gearbox in the A10 is still pretty raw, hence it's sitting at the back of the shed until I get another burst of enthusiasm....

[BSA_54A10]

This is where running multiple chains is worthwhile to do
Buy a lot of chains then drag a new one through every time the old one needs tightening
When all have been through once, adjust the chain run & repeat
I use cheap industrial chain , any brand provided the rollers are solid so the chain is softer than the sprocket because changing a chain is a couple of minutes
Changing a sprocket is an all day job on a good day

[Rex]

I'd never use cheap industrial chain as it's not made to the same specs as bike chain.
Some years back we had an industrial salesman visit my works to demonstrate and hopefully sell us a couple of rolls of chain. When I cracked a daft joke about "I'll be able to use some on my bikes" he visibly blanched and said don't even think about it, unless you want to have a quick-wear chain with risk of breakage.
After all, it's not as if proper bike chain is expensive.

[berger]

many moons ago i got the storekeeper to order me a big box of industrial chain for my bike. it lasted very well. possibly because it was genuine made in England and not that other stuff from we know where that has now flooded the market

[BSA_54A10]

Oils ain't Sols & chains aint chains
Light duty industrial chain has split rollers which look like the old steel conduit
Heavy weight industrial chain has full round rollers the same as motorcycle chain
Usually motorcycle chain is hardened  higher than industrial chain and will also have thcker pins
IT does wear faster but a 100' roll was only just slightly more expensive than a single quality chain
It also requires more frequrnt maitenance ut if you are pulling through then dropping it into a bucket for a week to degrease then it is a doddle

[Stephen Foster]

G'day Tony.
I was just contemplating doing that as well. I'm just putting a proper seal where the felt one was.
Yes a member has done that but he has been missing in action. duTch hasn't been on since Jan 2020.
Search his posts might find a pic or two, 300 pages! https://www.a7a10.net/forum/index.php?topic=4282.msg62295#msg62295 is a post with A65 types.
Cheers

[Stephen Foster]

Jim ,

On My plunger (1954) A10 ,

I have a slight but annoying oil leak which APPEARS to be coming from the Gearbox / Primary drive seal ..My questions  ..are new seals available & if so how are they fitted please ?

I cannot find individual parts number for the seal & I believe this would originally have been rivetted in place ..is there a more updated method or seal I could use please ?

I have never worked on a plunger a10 previously You see so all is unfamilair to Me yet .

Best Wishes,
Steve..

[Rex]

It's been a while since I was in there, but I recall drilling out the rivets and replacing the original seal with a modern garter seal then using small nuts and screws to refit the tin bits.

[muskrat]

G'day Steve.
It may be a bit hard with the motor & gearbox together but it is possible. I can't remember the seal size I used, 19mm id, 5mm thick, ?? od.
With the g/box removed I ground off the rivets (clutch side) and carefully popped out the heads. New oil seal was a nice snug fit in the case hole then sandwiched between the two plates and riveted back together from the g/box side.
Cheers

[Stephen Foster]

Thank You Rex & Jim .

Rex ,
Could You please let Me know the item I ought to source & where You obtained the seal please as We are both in UK ?
My plan is to wait until Winter to strip the engine down but I am trying to have all the pieces required to hand before I start .
The bike runs perfectly but has the slight leak .

Jim ,
please excuse My ignorance but I havent seen the seal other than in pictures ..which are the plates You refer to please ?

Thank You both again ,
Steve..
Steve..