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Discussion Starter #341
Pardon my ignorance, and I'm not as versed as others here, but you had no issues with the gearbox, and the only reason you took it out was because you wanted to change the sprocket.
Why not just fit the new sprocket and ride the thing. If you start developing issues in the future, you can revisit it with a little knowledge that there is some wear, but as you discovered it is easy enough to pull the clutch and gearbox.
Hi Jimmy

It would be great to have a proper explanation from the experts as to what we're looking at in the photos.

I'm going to run it as is until I find new gears at a reasonable price. There must be loads of bikes running around with tired gearboxes out there.

I just don't want mine to be the one that seizes up on a ride!
 

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Oooo. Plate Tectonics. This was only just beginning to be accepted when I went to Uni to study geology - a long, long time ago. Seems like a lifetime. It was 'new' then, but now seems so obvious. 'Spose it is a lifetime.
 

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Hi Jimmy

It would be great to have a proper explanation from the experts as to what we're looking at in the photos.

I'm going to run it as is until I find new gears at a reasonable price. There must be loads of bikes running around with tired gearboxes out there.

I just don't want mine to be the one that seizes up on a ride!
I was very fortunate to be mentored by an "old school" engineer who taught me many truths about basic engineering. One of the things be often "banged on" about was that "Mechanics only know how to throw parts at a problem, while an Engineer will analyse a situation and knows when (and why) to change parts and knows when he can take a calculated guess/risk to keep something going until it can be properly sorted out".

This philosophy can be applied to your gearbox. You cannot "unsee" what you have found, but you can make a calculated guess as to whether you can put it back in service in the short or medium term. What you have to decide is whether you are seeing potential imminent failure or will it hold on for now, while you accumulate the parts to sort the problem.

Terry
 

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Here we go after a good clean

Is there anything worth keeping here? I don't know what to look for, they mostly look OK to me apart from the rust and the pitting.

I'll start putting together a list of parts this weekend :(

Any harm putting it back as is until I can source all the bits?

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Hello Eli,
Just had a look at your new pictures, and they do not appear that bad - notoriuosly difficult to tell from photo's, you need to be pointing the camera straight at the "flanks" of the gears to show any pitting. You probably won't have a problem pro tem putting it back together and using with EP90 GL4 (NOT GL5) oil. Gear sets do come up from time to time, there's an early - ish set on eBay UK now, but take your time.
Cheers,
M!ck.
 

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Discussion Starter #345
Hello Eli,
Just had a look at your new pictures, and they do not appear that bad - notoriuosly difficult to tell from photo's, you need to be pointing the camera straight at the "flanks" of the gears to show any pitting. You probably won't have a problem pro tem putting it back together and using with EP90 GL4 (NOT GL5) oil. Gear sets do come up from time to time, there's an early - ish set on eBay UK now, but take your time.
Cheers,
M!ck.
Hi M!ck, thanks for this. I've been using Miller oils ep90 which is gl4. Big day at work but I'll order new gaskets, etc tomorrow and start putting everything back together. I've got a new sprocket to try!
 

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Discussion Starter #346
Christ almighty

Just lost an hour and all the nerves in my right hand trying to fit the kickstart return spring. Got it on once and stupidly decided to take it off again

Will attempt again tomorrow

Absolute hell
 

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Hi Eli,
using Miller oils ep90 which is gl4.
Mmmm ... given the expense of gearsets, you might want to consider some of the improvements in the last half-century? ;)

On the advice of a guy who used to work on triples at BSA and race them, I used Castrol R40 in gearboxes for many years (avoids the GL4/GL5 nonsense). Swapped to Redline Shockproof - Lightweight or Superlight - from the naughties. No worries the latter company's based in the US, there's certainly British retailers, probably French or at least EU ones.

Hth.

Regards,
 

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Discussion Starter #348
Hi Eli,

Mmmm ... given the expense of gearsets, you might want to consider some of the improvements in the last half-century? ;)

On the advice of a guy who used to work on triples at BSA and race them, I used Castrol R40 in gearboxes for many years (avoids the GL4/GL5 nonsense). Swapped to Redline Shockproof - Lightweight or Superlight - from the naughties. No worries the latter company's based in the US, there's certainly British retailers, probably French or at least EU ones.

Hth.

Regards,
Thanks Stuart. Does it smell better than ep90? :(

I've ordered a new kickstart spring and tab and also this part which looks like it's missing on my bike : kickstart pawl retaining disc (part 19 on pic below)

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And is the edge of the kickstart spindle that contacts the pawl supposed to look this rough?

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Thanks
 

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Discussion Starter #350
No. Get a new pawl and spring. Costs buttons.
Thanks Andy


There actually is a steel spacer hiding inside the layshaft lower gear

Is there a way of removing the kickstart spindle without undoing the mainshaft nut? It's fouling the mainshaft 3rd gear and it's going to be a nightmare to undo the nut with the box out

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Hi Eli,

'Fraid I can't remember. I thought the ks spindle simply pushes onto the end of the layshaft, and goes towards the primary side out of the outer cover. But IIRC, I had the ms nut off, so I think it's got to come off.

That ms nut's not that tight, which is why we put them back with blue Loctite - they have a habit of disassembly. If it's tight, try some heat?
 

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Discussion Starter #352
Hi Eli,

'Fraid I can't remember. I thought the ks spindle simply pushes onto the end of the layshaft, and goes towards the primary side out of the outer cover. But IIRC, I had the ms nut off, so I think it's got to come off.

That ms nut's not that tight, which is why we put them back with blue Loctite - they have a habit of disassembly. If it's tight, try some heat?
Thanks Andy. I'll have a go tomorrow

Parts are cheap but postage isn't and it takss forever to get here. I spend my days in the office hoping the postman has been!
 

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Discussion Starter #353
Hasn't budged with heat either. I'm using the old sprocket to pull against but no joy

My dad's dropping off an impact wrench I lent him tomorrow. If this doesn't work I guess I have to refit the box and chain to lock it using the rear brake

Ugh
 

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Hi Eli
If you have a pinion already out you might be able to press it against the two connected pinions in your photo, so the gear teeth lock up.
Regards
Peg.
 
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Discussion Starter #355
Hi Eli
If you have a pinion already out you might be able to press it against the two connected pinions in your photo, so the gear teeth lock up.
Regards
Peg.
Thanks Peg

This and a good burst from the impact socket did the trick

Replacing the kickstart shim won't do any harm :oops:

750498
 

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Discussion Starter #357
Now that everything is apart, then gears look OK to me but the bronze low gear Bush has a lot of play when on the layshaft. Is this normal (I'm guessing not even though everything is pushed together when the box is fitted) or should it be a tight ish fit?

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That bush really should have very little play, in fact I've just changed one on a 5 speed cluster - I had a second cluster to compare it. Replacing the bush is easy, just use the new bush to press out the old, but you will almost certainly need to ream the bush to a nice sliding fit. It can be done with an adjustable reamer if care is taken to keep the reamer square to the gear. I actually hold the reamer in a vise and feed the gear down a little at a time.
HTH
 

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The workshop manual data says the working clearance is 0.0015" to 0.003". I've not stripped mine down that far yet so I'm not sure what the typical wear pattern is like, but I would have thought with that fit (dry) it should fit on the lay shaft without significant radial play. You should be able to get a new bush 57-1393 to press in and repair it, but you might need to ream it to the correct size after it's pressed in (shaft size is given as 0.689" to 0.690")
 
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