Primary Chain/Sprocket Wear

[BagONails]

I was thinking about this. I'm going to make the stub driver as described by Swarfy and will use my rattle gun to undo the nut. For retightening I'm thinking I can use the scrap primary chain to make a chain wrench that will fit over the new sprocket and resist the tightening torques.  I have a similar smaller tool for tightening gear cassettes onto push bike freewheels, works a treat. This way no forces are transferred into the crank or clutch etc. Another good heads up Col, cheers.

[Black Sheep]

RD Fella.
Example 1. Norton 99, Edinburgh to Bristol, primary chain soaked in Linklyfe, otherwise chaincase empty. The primary chain lost most of its rollers on that one trip. 
Example 2. Velocette MSS, Edinburgh to Helmsdale and return. Had forgotten to add oil to primary chaincase after gearbox rebuild. Chain stretched to oblivion.
Perhaps if you ride very gently and oil the chain very regularly yoy will get away with it. I didn't.

[Colsbeeza]

BoN - like this?

[BagONails]

BoN - like this?

That's it! Oh well no patent royalties for me then.

Cycling types call them chain whips.

Looks like an excellent anti theft device, is that how you park your bike for max security or are you in the midst of similar primary dramas Col?

[chaterlea25]

Hi All
The clutch chainwheel looks fkd to me!!
Beware of the cheaper Indian made chainwheel, badly made and soft as cheese
The good ones usually have a Triumph part number stamped on them

John

[Colsbeeza]

Hi BoN,
No I did that a couple of years ago, until I thought about the cush ramp/cam issue. Anyway it locked the sprocket real good!
Col

[chaterlea25]

Hi Ian,
Here is a link to a topic I posted on the ins and outs of primary alignment

https://www.a7a10.net/forum/index.php?topic=9646.msg70166#msg70166

John

[BagONails]

Hi fellas, Quick update with pictures and further questions...

I found an old 36mm 3/4" drive socket in the bottom of my tool box which looked about right for getting the cush drive nut undone, Damn that chrome/vanadium steel is tough! Oh and as it turned out there was no split pin in the end of the crankshaft and the cush drive nut was up tight but not that tight....

As luck would have it a 22mm socket with (double hex) fits perfectly over a 3/4" square - a right result!

The primary chain looks well knackered as expected

The centre nut looks like the original 6 speed item, seems to be doing the job although when the home made tab washer was released the nut didn't feel particularly tight and undid too easily, this should have been at 65 ft/lbs...The clutch adaptor is still fixed tight on the mainshaft however, hopefully the taper and key are still good.

Question 1: Can I use a small bearing puller to remove the adaptor from the mainshaft rather than making another special tool?

Notice how the inner chain case is pulling away from the crankcase at the front, I can see the need to carefully check all alignments and rear mounting spacer width with dummy 5/16" screws clamping this up before final assembly with the new parts.

Question 2: Although the centre nut was done up and the adaptor is firmly fitted on the mainshaft I noticed the clutch basket had a fair amount of rock once the clutch nuts were undone. Free play can only be within the clutch bearings although the rollers and bearing surfaces all look OK, fine burnished/polished appearance on all surfaces, no pitting or galling there was even a little grease still in there! (I really don't know what P/O thought was going to lubricate these bearings long term tho.) There is no thrust washer as far as I can make out.  Has anyone looked at fitting a sealed ball bearing that can take the axial and thrust loads and reduce this free play which must add to clutch drag issues I would have thought as it would be pulled out of line by the primary drive chain tension when the clutch is released? (OK more than one question sorry)

Question 3: I measured gearbox mainshaft end float of 0.4mm does this sound OK, seemed a bit much but hopefully not an issue?
 

[chaterlea25]

Hi Ian,
If you can get the puller jaws behind the adaptor it should work, otheres have used a split clamp type yoke to get behind the adaptor....
It looks as though the spacers at the rear mounting of the chaincase are too thick pushing the rear of the case inwards? so the front pops out when the 3 front fasteners are undone ??? NOT GOOD!!! the rear spacers should just fill the gap when the front of the case is tightened up

You have the wrong clutch nut, The correct hex nut has a thick (5mm) washer behind it to clamp the inner drum onto the adaptor
First time I have heard of a six speed BSA gearbox   

The centre nut looks like the original 6 speed item

   

There is usually some wobble on the chainwheel, It should be reduced to a minimum when the inner drum is bolted up, fit new rollers as well 0.250 x0.236in.
I have not come across a bearing that will substitute those rollers.....

There should be almost zero endfloat on the gearbox mainshaft
The shaft is clamped to the kickstart side ball bearing
Either the nut is not tight or the bearing is worn  (All else being OK)

John

[BagONails]

The correct hex nut has a thick (5mm) washer behind it to clamp the inner drum onto the adaptor

Yes I found a different nut and washer and tab washer listed, the thick washer is dished so it clamps the hub back against the shoulder on the adaptor I take it.

If you can get the puller jaws behind the adaptor it should work, otheres have used a split clamp type yoke to get behind the adaptor....

it worked a treat thanks!

There should be almost zero endfloat on the gearbox mainshaft
The shaft is clamped to the kickstart side ball bearing
Either the nut is not tight or the bearing is worn  (All else being OK)

John

Oh gawd the trail of destruction leads on into the gearbox...

After taking the inner primary off this evening I turned it over to look at the back and found the final drive chain has been milling away at it because the case has been flexed so far over by the huge spacer at the rear mount. This could have turned into the mother of all oil leaks 

 I also found the nut holding the final drive sprocket was loose, only the very tired looking tab washer was holding it on. And so it continues!

[Colsbeeza]

Hi BoN,
 If the inner case is saveable, I recommend the approach that I took.
First - check that it mates well with the outer case.
Secondly - place a straight edge along the gasket surface of the motor and measure the stand-off at a couple of points along the gearbox/engine mounts. This is to check that the engine is square with the frame and mounts.
Thirdly - screw the inner case to the engine using the 3 studs and check that the clearance behind the rear mount is only a mm or two.
Between these checks you may find (probably will) the inner needs some panel beating. I laid it down on the bench with some rag underneath and gave it a few strategic whacks with a rubber mallet. A good eye helps decide just where to whack it. It was surprisingly pliable and no hint of cracks or damage. At your own risk of course! Then a final check that the inner and outer mating surfaces don't have any large gaps.
Step 4 - If all fails, look for another inner case.!
Col

[BagONails]

After removing the outer cover on the gearbox I found the K/S nut to be tight and I can see the mainshaft and the inner bearing race moving together. I measured 0.4mm (0.016") end float so this now appears to be wear in the bearing itself.  The kickstart gear is also showing a fair amount of wear.  At this stage I don't want to get into a full gearbox rebuild and my test rides so far have not shown up any obvious issues apart from some difficulty finding neutral. It was quiet and gear changes were smooth enough, no whining or jumping out of gear etc. I suppose I should ask at this point what are the likely symptoms of a worn mainshaft outer RH bearing and how much of an issue is it in fact?

I'm considering now following the service sheet 311 which says I can pull the mainshaft out of the gearbox as an assembly complete with the inner cover, after removing one more screw. This should then allow me to undo the kickstart nut, strip everything change the bearing and the kick start gear (if I can get one) on the bench while leaving the rest behind in the shell.  Reassembly is simply the reverse of disassembly...now where have I heard that before

It would be good to hear from anyone who has done this and what issues may be hidden for young players, it all sounds too easy somehow...

[Swarfcut]

 To swap out just that ballrace, the inner cover and bearing can come away after the mainshaft nut and kickstart ratchet, pinion, bush, spring and washer are slid off. This leaves the mainshaft in place. This procedure is outlined in Service Sheet 209, for Plunger boxes.

 If the clutch is already dismantled the mainshaft can be removed complete with the inner cover as in Service Sheet 311. With the mainshaft gears left in situ, replacing the mainshaft may prove a challenge, lining up the splines. Easier on a loose box, more tricky perhaps with the box still on the bike.  Both Plunger and S/A boxes share similar layout, and on the face of it the dismantling procedures should be the same, but as they say there are more ways to skin a cat, so proceed as to what suits the situation.

 Outer race is a press fit in the inner cover. Warm the casting and it will drive out easily. New bearing in the freezer, warmed case and it will fit with no drama.  Check the seating for wear and also the condition of the retaining spring steel snap ring. When replacing the inner cover, ensure the selector shaft is lined up with its location in the inner cover. Unintended  pressure on this shaft will break away the retaining grubscrew location adjacent to the chain sprocket.

 Kickstart gear comes in two variants of tooth profile. If replacing, make sure it matches the quadrant teeth. All explained in previous Forum posts, it's just a matter of searching.

 Swarfy.

[berger]

swarfy's first way of doing this is the way to go leaving the mainshaft in the box otherwise the selectors and gears may move making it a bit awkward on re assembly. when pulling the inner case away keep your thumb on the mainshaft end to prevent it pulling out and letting these bits slip out of place.

[BagONails]

Thanks guys, my main concern was how tight the mainshaft would be in the inner race of the bearing which would be a problem for disassembly and reassembly with the new one but if not too tight then leaving the shaft in situ sounds like the go, I will find out in the morning