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#853301 07/08/21 5:14 pm
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Hello everyone... A proper newbie here, and unfortunately for you lot...
I am completly new to forums - never joined one in my life, until now. So excuse me if I get something wrong in terms of posting because I have no idea what the "form" is.
I know absolutely nothing about old British bikes - never owned one (until now) and I've only ever ridden 1 Triumph, and that was 35 years ago!
I've just bought a 1956 BSA B33 unseen/untested from an auction and I'm now trying to get to grips with what I have. I haven't even started the bike yet (don't actually know where the on/off switch is!), but I am beginnig with the most obvious problem (see below).

There is a tiny bit of good news... When I had a proper job, I was a mechanical design engineer - so mehcanically-speaking, I have some idea. And I've owned and worked on many Jap and Italian machines (and restored a couple) over the past 40 years. My problem is that all of my experience is on 1970's or later Jap/Italian bikes, and I know absolutely nothing about British bikes.

So, to my first questions...

When the bike was delivered, I immediately noticed that the clutch action was massively heavy (about 21kg of force was required to pull the lever in). My first thought was that it must have the wrong springs or too much preload on the springs - so I removed the primary cover and sure enough, too much preload. I measured the free length of the springs and all are between 25.2 and 25.7mm (so 1" nominal length springs, which is OK I think). I don't have a spring tester but I rigged something up with a bit of 4x2 and a bucket of water (don't ask!) and determined that all spring rates are between 203 and 217 pounds/inch (again, OK I think). I also checked the Sureflex friction plates, and they have plenty of life in them. I then set the springs with 2.5 turns of prelaod on each (I'd read that somewhere), and then the clutch felt fine, the pressure plate seemed to lift fairly squarely, and I was able to kick over the engine (without using the decompressor) with no clutch slip. Which begs the question - why was there so much preload on the springs?

When I removed the primary cover, about 1.2 litres of very dirty oil came out, which I think is way more than the primary should have. So maybe the clutch was slipping and the previous owner wound up the preload to stop the slip? Or maybe he just didn't know and wound the spring nuts on until he thought they were tight enough? And in the bottom of the primary case, there's lots of slightly gritty black sludge (as you might find in the bottom of a sump). And the engine oil level is about 5 inches below the line on the tank (which is probably about a litre too low). So I think the crankshaft seal must be shot (or non existant), hence all the dirty black oil in the primary drive. Would you agree?

I also noticed about 1mm of end float on the clutch basket - so if you grab hold of the basket and push/pull it, the basket and driven sprocket move in and out together by a total of about 1mm (this is accompanyed by a "clonk-clonk" noise as the basket moves back and forth). Is this normal? It doesn't seem right to me, but maybe there is supposed to be some end float to allow for misalignment between the driven and driving sprockets?

And I noticed some minor grooves/notches worn into a couple of the driving faces on the clutch basket, which really need to be dressed with a file - but there's a cylindrical tin shround around the basket that stops you doing that. The shround doesn't look easy to remove (looks like it's pressed on) because it's quite thin and you can't get on the back of it to try to tap it off because the driven sprocket is in the way. Maybe I'm missing something obvious, but does anyone have any thoughts?

Thanks in advance.


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Your engine wet sumped (through the feed gears in the oil pump) and then the engine oil made its way to the primary. Check your oil tank, if its empty you know where it went.

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B33s are not my thing but i can help a little.
DPO (dumb previous Owner) probably the reason for the clutch springs wound in too far.

Excess oil in the chain case , it was either overfilled or from the sounds of it the seal at the crank main bearing failed.

End float , alarming , yes, normal, sadly also yes.At least with later twins this is normal, pre unit singles may be different , some one will chime in.

Clutch basket grooves, not ideal and may cause the plates to snag, which can spoil clutch action, might be the reason the springs were wound in, these can be filed clean, equal strokes for each groove, once the clutch is stripped and on the bench.


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Originally Posted by tracksense
the clutch action ...
You should find the information in this thread useful.

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Welcome to the wacky world of British Bike ownership, here are my thoughts on the issues found so far:-
- it's possible that a previous owner had experienced clutch slip and thought that tightening the spring nuts as much as possible was a good idea. If clutch slip was the problem then this could have been caused by using a modern type oil in the primary which is incompatible with wet clutches. Ideally you should use a motorcycle oil with the JASO MA spec or a classic car oil with API grade no higher than SG.
- its interesting that you mention that Surflex plates are fitted, this suggests a previous owner has also tried to fix a slipping clutch by fitting better plates. I would clean the friction and plain plates with solvent to remove any residual oil and other contamination.
- sounds like you have a wet sumping problem whereby the oil from the tank slowly drains into the sump and then eventually finds its way into the primary whilst left standing for several months. This is very common on all British Bikes and there is no easy cure for this apart from trying to slow the drainage by ensuring the oil pump doesn't have any leaks past the gears. Don't try fitting a one way valve in the oil feed from the tank as this is could lead to oil starvation and failure.
- the clutch end float doesn't sound right, I would check the mainshaft and how its supported by the gearbox bearings.
- I would replace the clutch basket with a new one, unless the grooves can be easily filed out.

Last edited by gunner; 07/08/21 8:37 pm.

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Hi, tracksense,

First of all, there is no on off switch, magneto ignition and use the valve lifter for starting and stopping the engine
Get a riders handbook which will explain the extra control levers on the handlebar and a set of BSA service sheets, a parts book is also very useful
First check that the clutch centre nut is fully tight, Fully FT as Guy Martin would say!!!
If that's OK, open the oval inspection cover on the kickstart side of the gearbox, Inside you will see a bearing retained with a circlip behind the kickstart ratchet gear.. check for movement in the bearing (wear) or if the shaft is moving inside the bearing because the ratchet retaining nut is not tight
You will also find a lot of clutch and gearbox information on the BSA A10 Forum as these share the same components
https://www.a7a10.net/forum/index.php

John


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