slipping clutch

[bsa-bill]

I use a modern multigrade in the primary without issues at all

as for modern oil having friction modifiers, isn't that what oil is and has been since Adam was a lad, and if the suggestion is modern oil will make your clutch slip then get some in as more of us will have a problem with clutch drag than slip  I reckon ( just though I'd mention like  )

[Topdad]

I just use mono 40 grade which come to think of it is probably why I have to back the cable right off on first start but apart from that I've had no other issues.

[Sam C]

Wow.

Thanks all - plenty of food for thought there.

This has left me suitably respectful of the workings of an old motorbike clutch, and aware that oil types are rather more important than I'd expected, and (weirdly to me) it would appear that oil, to some extent, is meant to be on the clutch plates provided its the 'right type of oil'. Is that right?

For the time being I am going to leave well alone until I'm sure I know what I'm doing. Seems much more complex than a car clutch to me.

I really appreciate all the comments - this is proving to be an extremely helpful forum with really knowledgeable people using it (wish I could say the same for the various car forums I've used in the past for older cars!). A10s clearly attract a better breed of spannerers!

One final thing: My bike was stood for a few months while I did my lessons and passed my test. Consequently when I first fired it up it dumped a fair amount of oil straight away out the bottom of the bike: I think this is normal and to do with the oil working its way back through some sort of vale, into the wrong place. Running the bike is meant to move the oil that's not been dumped back to the 'right place'. I therefore simply topped it back up using the same type of oil as had been used before, and using a torch I checked that the oil seemed to be circulating by looking in the tank: and it was spurting away as I think it should.

But could that action of oil 'ending up in the wrong place' have caused oil to get onto the clutch plates though? Similarly could the oil be wrong (it's what the previous owner used - my stepfather in law - who generally knows what he's doing).

The oil I used is Classic Motor Oil SAE40 and I simply topped up what seemed to be the oil tank right next to the batter (on the right hand side looking from the back of the bike).

Thanks all - the questions and long posts will ease off in a bit I hope!

Cheers

Sam

[a101960]

Sam, you are correct in your assumption that the oil was dumped because the bike had stood for a while with out being started. The oil drains under gravity from the oil tank into the bottom of the crank case (the sump). How quickly this happens depends on a number of factors. To prevent this happening again, before you start the engine remove the oil tank cap and check out the oil level in the tank. If the level has dropped substantially then it is quite likely that when you start the engine the oil in the sump will be forced out via the engine breather. That is what happened to you on this occasion. The simplest way to deal with this problem is to buy and fit a sump plate/cover fitted with a drain plug. If the bike has a tendency to drain the oil down then it is a simple matter to undo the plug and drain off the excess oil. You can then pour the oil back into the tank. I think you will find that is what most A7/A10 owners do. Obviously you do this before attempting to start the engine. Some people blame wear in the pump for this problem, and some say the cause is the anti drain valve not seating properly. Having said that I know of people that have fitted new pumps and still had the problem. To rectify the valve a complete engine strip is required. Most people just learn to live with it until a complete engine rebuild becomes necessary. Just get your self a sump plate with a drain plug. Oil could get onto the clutch if the crank case has filled up with oil, it depends on how much oil has passed from the engine into the chain case. By the way, a word of warning. Do not top up the oil tank if the oil has drained down to the sump. Once the oil is circulating there will be to much oil in the system and it will find its way out again making a mess all over the floor, or all over your leg if you ride off.
John

[Sam C]

Thanks A101960 - very clear and helpful explanation.

No idea if I have a drain plug, but I'll take a look. And thanks for the tip on not filling up - I did guess at an amount broadly equivalent to the puddle on the garage floor and fortunately I didn't seem to get any more spurts of oil anywhere. So hopefully it's alright.

HOWEVER: I am intrigued by the possibility that this has resulted in oil ending up on the clutch.

Reading everything that's been written this is what I think I've learnt:

he chain chase is meant to have a little bit of oil in the bottom of it. The chain moves through this oil, ensuring it always remains lubricated (so no need to 'oil the chain' as I've heard people talking about: the oil in the chain case will do that for you).

Given that the clutch is in the same place (i.e. inside that chain case), some oil inevitably gets onto / into it, but that's normal. The key is for there to be little oil on /in it rather than none at all. It's not like a car clutch which must be spotlessly clean and oil free.

If oil does get into the clutch (I.e onto the clutch plates) then depending on the amount that can cause slippage - since it's a lubricant! - but it can take a bit of oil. However, if oil does get in, centrifugal force ought to force it out again in time but I guess that depends on the type of oil - thin oil will spin out quickly, thick oil slowly or not at all.

You use different oil in the chain case to the oil that you put in your main oil tank in part because you're lubricating different things (an engine in the case of the latter, a chain in the case of the former) and because thicker 'engine oil' is more likely to end up with a slippy clutch if it gets onto that.

Sound right?

Sorry: steep learning curve to begin with!

[morris]

thicker 'engine oil' is more likely to end up with a slippy clutch if it gets onto that.

Or a sticky one...! DAMHIK
But since going to hydraulic ISO 32 grade (equivalent of a 10W monograde) the clutches on the plunger as well as on the SA behave flawlessly.

Regarding your question about engine oil in the chain case, there's no connection between crank case and chain case. If the crankshaft's oil seal and the two bolts that hold the inner case to the crank case are ok, no engine oil can find it's way to the chain case.

[RichardL]

Nevertheless, check the level of your chaincase oil/ATF by whichever method is used on your bike, either an overflow screw one back from the bottom large screw near the front of the cover, or an overflow screw screwed into a bottom drain plug in the case cover.

Richard L.

[Greybeard]

...You can then pour the oil back into the tank...

My take on this is that oil is not so expensive that I would risk using possibly contaminated oil.

By the way, a word of warning. Do not top up the oil tank if the oil has drained down to the sump. Once the oil is circulating there will be to much oil in the system and it will find its way out again making a mess all over the floor, or all over your leg if you ride off.

Oh yes, I recently made that mistake!

[worntorn]

Sam, I will add that ATF is grippier than any motor oil I have encountered and that TYPE F ATF is the grippiest (not sure that's a word) of the ATF types.
Type F ATF fixed my slipping /dragging Norton Commando clutch years ago and now this BSA A 10 clutch. I didn't even disassemble, just drained off the old oil and replaced with clean ATF, rode 50 miles, drain off the ATF and refill with new ATF.
This really cleans things up in there.

Glen

[RichardL]

This really cleans things up in there.

Hmmm? I guess that's because oil is all over the place in there. 

Richard L.

[oldbeezageezer]

Sam
Re your oil dump. When the bike stands for a while the oil does drain t the bottom and is generally called 'wet sumping'. They are all prone to this. Mine has a had an on/off valve which looks suspiciously like a plumbing 'ball-a-fix valve fitted in the supply line by the previous owner. The down side is that it is under the gearbox and out of sight. I turn it off when I put the bike in the garage if I am not riding it for a while and turn it on, obviously essential, if I am going out on it. One of our BSAOC members has fitted an old gas valve to his and run it on top of the gearbox so it is easy to see whether it is on or off before you go out. I will scan a photo of it and re post that later.

Good that you are taking the time to 'gen' up on the workings of the old bike and making use of the wealth of knowledge here. I did, and probable still will whenever the need arises.

Alan

[oldbeezageezer]

Sam
 One of our BSAOC members has fitted an old gas valve to his and run it on top of the gearbox so it is easy to see whether it is on or off before you go out. I will scan a photo of it and re post that later.

[oldbeezageezer]

Managed to get bike back together and out on the road. New 4 spring clutch from SRM works well although it wants a bit of tweaking. Disengages fully on half pull of lever but practically have to have the lever fully released before it bites. One success,,, I can select neutral at standstill!

Also electric ignition seems spot on and 12 volt lights all working and charging just above tick over.

Indicators next I think.

One problem with road test. After about a mile suddenly heard a loud, brief scary metallic sound from the left hand side then a swishing noise. After the initial noise it it did not have any effect on the running and got home ok but just with the swishing noise.

I am almost sure the that the noise is caused by the cush drive nut that has come undone. PO had omitted a tab washer and put a cut down nut on the shaft. The inside of my chaincase already had a groove in it but I, doing things as the book. added the tab washer, tightened the cush drive nut with a C spanner and then a few hefty clouts with a hammer and punch and inserted a split pin.

Now got to remove the chaincase again, new gasket, oil etc and probably put the PO nut back on or get SRM's cush drive nut. Bugger.