BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: Phil C on 29 November, 2021, 14:01:25

Title: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 14:01:25
Please have a look at this photo (1965 B40F.) Clearly there's somehow an oil leak.  What's that all about? Could anyone advise please?   Thanks in advance.   Phil
Title: Re: Oil leak at front wheel
Post by: Derek996 on 29 November, 2021, 14:09:30
Possibly too much grease in the bearings that has melted and leaked out
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 14:13:30
Hasn't happened before. Could it be grease coming from the brake?  I'm guessing not.  Phil
Title: Re: Oil leak at front wheel
Post by: JulianS on 29 November, 2021, 14:26:05
I think the brake would need to get very hot to melt the grease in the bearings and I think it would run into the drum rather than onto the outside of the brake plate and you would notice a lack of brake.

Check for a leak from the fork oil seal.
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 14:43:21
Just been out to see if it's been running down the fork slider. It's a little bit oily but I don't think so. Looks like it can only be, as Derek said, grease from the bearings? I guess it's nothing to worry about and if it's an excess of grease then it will stop of it's own accord?   Phil
Title: Re: Oil leak at front wheel
Post by: Editor on 29 November, 2021, 14:50:20
I'm not familiar with these forks so a bit of a longshot but, do your B40F forks have the tapered peg pointing skywards inside the slider at the bottom. This is the standard way of damping the forks on compression.
If so, the peg is bolted in from the bottom and should have a fibre washer in there to stop oil leaking - for life. If said fibre washer is missing or perished then oil can seep through.
Again I might be talking through my backside but maybe worth taking the wheel out and seeing if oil is coming from the recess in the slider?
Chris
Title: Re: Oil leak at front wheel
Post by: JulianS on 29 November, 2021, 15:21:02
If you think it is grease then I suggest that you check the brake for contamination.
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 15:32:33
Chris, l'm not familiar with forks atall. So far in my "apprenticeship" in this hobby I've done nothing with forks except drain and renew the oil. I guess at some stage I need to commit to taking them to bits in order to learn. I don't even know where the recess in the slider is.  Phil
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 15:33:34
If you think it is grease then I suggest that you check the brake for contamination.

Brakes worked okay this morning when I was out.
Title: Re: Oil leak at front wheel
Post by: DAVE BRADY on 29 November, 2021, 16:04:10
Hi,

I would suggest cleaning it all off the brake plate and anything on the fork leg right up to the top.  Pump the forks quite vigorously to simulate riding and see if anything is coming out of the fork seal.  If not go for a ride and then see where it starts to come from.  For the grease to melt you would have be riding along with the brake held partly on to generate the heat needed.  I have only ever seen the grease melt once and that was in a rear hub after an enthusiastic decent of the Ballon d'Alsace.  The brake will usually fade before getting this hot.
It surprising how a very small amount of oil will gather at a drip point and look like a lot.
Have you topped up or changed the fork oil recently?  Just a bit too much will need to escape.  If you determine that it is wheel bearing grease do as suggested by Julian and strip the brake out.  The brake may have been working this morning but you really do not want to find out when it does not.  Better safe than sorry and think about the potential damage to your B40.

Dave.
Title: Re: Oil leak at front wheel
Post by: AdrianS on 29 November, 2021, 16:54:57
Melted grease during this cold weather - I think not.
Wash and clean everything from the fork seal holders downwards as suggested and keep an eye for future traces of oil.
All 3 of my BSAs suffered from fork oil leaks and if itís not the drain screw fibre washer leaking itís usually a fork seal or a poor seal between the seal holder and lower fork leg.
Before you can do anything, you must diagnose the problem!
Title: Re: Oil leak at front wheel
Post by: Mike40M on 29 November, 2021, 17:04:28
Adrians advice seems a good starting point. If cleaned, you might be able to find where the leak is.
The drain plug washer or the damper washer as likely source of the leak. Not unusual with drain plug leaks if reusing the old one.
It should be easy to find out if fork seals are  source of the leak as described in earlier posts.
Checking the single side sealed wheel bearing can be done when you take off the wheel.
Title: Re: Oil leak at front wheel
Post by: chaz on 29 November, 2021, 18:18:39
same as the forks on the B40 Im working on.
one drain screw has sprung a leak , no pressure on it as bike on a stand with wheel off the ground, new washers, it just happened one weekend.
the fork leg seems to be a welded assembly , a seam might have sprung a leak, or another possibility, being split caps is that a tapped hole may be too deep and broken through into the fork oil chamber. Both of these could be aggrevated by movement  and vibration.
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 November, 2021, 18:31:59


Phil
same as the forks on the B40 Im working on.
one drain screw has sprung a leak , no pressure on it as bike on a stand with wheel off the ground, new washers, it just happened one weekend.
the fork leg seems to be a welded assembly , a seam might have sprung a leak, or another possibility, being split caps is that a tapped hole may be too deep and broken through into the fork oil chamber. Both of these could be aggrevated by movement  and vibration.

Split caps? What, and where, are they?   Phil
Title: Re: Oil leak at front wheel
Post by: idie on 30 November, 2021, 13:48:00
He means the caps that hold the spindle to the bottom of the forks on full width hubs.
Title: Re: Oil leak at front wheel
Post by: chaz on 30 November, 2021, 16:07:38
It  looks like the bottom of the fork leg has a pair of bolts holding the axle in, other B40;s from 1965 have full diameter holes with a clamp bolt behind, so the bottom half of the leg is called a cap or clamp. on my A50 and more modern bikes with conventional forks the damper assembly is is fitted in the bottom of the fork leg with a bolt which is removed by the aid of the bottom cap.
my eldest bought a modern KTM with the old style single bolt clamp and it wasnt until we were cleaning the bike one day that we noticed the clamp was split and held in with superglue, he bought the bike from someone who worked at Heathrow airport.
if one of the cap bolts is too deep, it might break through into the leg where the fork oil sits.
Title: Re: Oil leak at front wheel
Post by: Phil C on 06 December, 2021, 14:35:26
Afternoon everyone,

Just an update, to keep you interested :)  -   just been out to the garage, cleaned off the brake plate and the fork leg, and pumped the forks about a dozen times. No sign of any oil.

Next step is to go for a (careful) ride and see what I can see then.

Given that no oil was evident after pumping the forks just now, maybe it is wheel bearing grease, as Derek996 suggested. It does look like that's where it's coming from on the photo, don't you think?

Any thoughts appreciated!

Phil
Title: Re: Oil leak at front wheel
Post by: JulianS on 07 December, 2021, 10:39:01
Phil

I have already suggested a way forward and other members have offered opinions and nothing appears to have changed since then. I do not for one minute think that the oil on the brake plate is melted grease from the hub.

If you look at the cross section diagram of the iron full width hub setup below you can see that if the bearing grease has melted it would drip into the hub, not squeeze out along the wheel spindle and leak over the outside of the brake plate.

If you think it is bearing grease then you have a duty of care to other road users to check that your brake is safe and not contaminated.

It is easy enough  to remove the wheel and detach the brake plate to check.
Title: Re: Oil leak at front wheel
Post by: Colin SS90 on 07 December, 2021, 11:14:12
I agree with the opinion that it is not melted grease.
I would further investigate a fork leak as just pumping the forks does not simulate the forces from riding which induce much more fork travel and can maintain fork compression forces under braking. Also if the fork oil level was too high initially the excess may have already leaked out resulting in a leak free level.
Title: Re: Oil leak at front wheel
Post by: BEESY on 07 December, 2021, 11:54:28
Have you taken the wheel off and had a good look at the forks?

That and taking the brake plate off the wheel would be the 1st things I would do.
Title: Re: Oil leak at front wheel
Post by: AdrianS on 08 December, 2021, 10:17:15
Do as I suggested in an earlier post. Whether you take the front wheel off is up to you. As I said it is highly unlikely to be bearing grease.
Clean everything off properly and see if a leak appears. If ok take the bike for a run and recheck.
It is very easy to overfill the forks. If you drain them through a drain plug, quite a fair amount remains within the fork even after pumping.
If you have a genuine leak, the main places are the drain plug, the fork seal holder and I suppose even from above the seal holder if the seal fails and a large excess of oil is put into the fork.
Title: Re: Oil leak at front wheel
Post by: Pete Gill on 09 December, 2021, 14:47:36
Hi Phil

I can not see how that could be grease. From what i can see from the tracks and the way its run its got to be oil. I would be convinced by the way it feels to touch under your finger.
At these temperatures (? 5 deg C ) in the garage this time of year grease would feel very waxy and firm under the finger but oil will still run and actually look like oil and glisten on the finger.
It looks like oil from the fork to me.
Title: Re: Oil leak at front wheel
Post by: Phil C on 10 December, 2021, 14:06:10
Hello all,

It didn't seem runny enough to be oil, but maybe it was dried by the passing air on the ride, and/or the coldness of the air - dunno. Maybe it had been there a while and I'd not noticed. But anyway, general consensus seems to be oil rather than grease. Fair enough, I expect that's right.  Went for a short run this morning - just two or three miles - and there was little if any on the brake plate when I got home, maybe a little bit, and some around the brake plate nut - hard to tell much very precisely because of raindrops all over the place (unexpected shower, but actually, living in South West Devon, not all that unexpected.) I'll look into it further as soon as I get time (moving house next week so a bit pushed for time at the moment), including taking the wheel off and having a look at the brake. Looking forward to that, and maybe also then taking the forks apart to learn about them. If and when I do that you can expect a flurry of dim questions.

Phil
Title: Re: Oil leak at front wheel
Post by: Pete Gill on 11 December, 2021, 17:21:45
I look forward to hearing your findings Phil, we all learn from these things.
Pete
Title: Re: Oil leak at front wheel
Post by: chaz on 11 December, 2021, 19:35:36
trouble with fluid, is it collects dust. this then solidifies, more dust and more oil ends up like grease.
left long enough it will stain, especially if old and contaminated with brass and aluminium that is inside the forks.
Title: Re: Oil leak at front wheel
Post by: Phil C on 20 December, 2021, 22:03:02
I needed to ride the bike yesterday, in order to get it to the house I'm moving to. The distance I travelled was about the same as I had gone when I noticed the oil which started this discussion. This time there was no sign of any oil streaked down the brake plate. And btw the brakes seemed to work okay.
Maybe the trouble was that when I drained and renewed the fork oil a few months ago I put in a touch too much oil, which then found its way out until the level was correct. But I was pretty careful in measuring it out, so I'd be surprised if that's the case. I guess there's no way of checking the fork oil level other than draining it and renewing with a measured amount. If there's been a leak then I imagine there might be no oil now left in the forks, so maybe I should remove the drain plugs to see, drain any that's in there, then put in the right amount, and see what happens. All advice/thoughts appreciated as always.   Phil
Title: Re: Oil leak at front wheel
Post by: AdrianS on 22 December, 2021, 09:50:56
The problem is that just opening the drain screw does not drain all the oil out. Iíve left the screw out and pumped the forks before removing them for a rebuild only to find quite a bit of oil still inside.
Title: Re: Oil leak at front wheel
Post by: DAVE BRADY on 22 December, 2021, 09:59:54
Hi,

Even with the top nut removed some oil will remain.  I have found the best way is to leave the top nuts in place and with the drain screws removed pump the forks until no more oil comes out.  Beware though the oil will squirt a good way so drip tray rather than a jar is essential.

Dave.
Title: Re: Oil leak at front wheel
Post by: Phil C on 22 December, 2021, 10:00:15
So, after I drained the forks a few months ago, including pumping, I might have still had some oil in there when I put in the measured amount, and the two together added up to too much, which then found a way out.  OR, I might simply have a leak and there's now no oil left in there at all. I don't see any way of checking the latter without opening the drain screws.  Phil
Title: Re: Oil leak at front wheel
Post by: TTJOHN on 22 December, 2021, 10:35:31
Phil.
Sorry only just picked up this thread. Have you check the shuttle valve stud at the bottom of the forks? this is usually where the trouble lies, the drain plug on the forks has a turned down bit at the end which fits into the shuttle valve recess of the shuttle valve stem to stop it from turning sometimes these are badly damaged, from tightening up the stem, the stud at the bottom is a small hex head stud with a 1/2"BSF thread, this should have a fibre & a plain washer on it. HTH

Regards TTJohn
Title: Re: Oil leak at front wheel
Post by: BEESY on 22 December, 2021, 10:54:01
Do you think that if the leak was caused by over filling then the leak would have shown itself straight away?

By wiping the oil away without tracing where it came from, you removed the best way to find the leak.

You could refill with oil and see where it's coming from, but that only gets you back to where you were originally, or you could take the wheel off to see what that might reveal.

Barring a crack in the fork leg itself, there are only really three or four places it can come from, the drain screw, the shuttle valve stud (if fitted, not 100% sure on your model), the oil seal and the top nut.




Title: Re: Oil leak at front wheel
Post by: AdrianS on 23 December, 2021, 10:18:09
Oil leaks from overfilling donít always show up immediately unless a large excess was introduced which takes the level to or above the oil seal holder. The oil seal will stop splash oil but probably wont stop pressurised oil when the forks are in use. You are also relying on the seal of the oil seal holder threads to prevent oil leaking down the fork leg.
If in doubt, it is not difficult to remove the leg, strip and rebuild it and fill with the correct amount of oil.
You only need to buy a seal for a couple of quid if the bushes are ok. Very often the seal holder can be unscrewed without the use of the special tool but Iím sure someone will loan you the tool if necessary.
Title: Re: Oil leak at front wheel
Post by: Phil C on 23 December, 2021, 17:19:04
The bike is a 1965 B40F, so the forks are Heavyweight.  I don't think there's a shuttle valve (whatever that is!)
I think I'll probably remove and strip down the leg (never done it before, so will be learning as I go along.) Looking at Rupert Ratio, vol 2, p.60, it appears the only must-have tools are an oil seal holder fitting/removal tool, and a stanchion puller (fork leg fitting/removal tool.).   Phil
Title: Re: Oil leak at front wheel
Post by: chaz on 23 December, 2021, 19:26:13
if you dont have the special tool, and are intending to do the job when the specialist shops are closed, you might try
https://www.eurocarparts.com/p/masterpro-rubber-strap-oil-filter-wrench-6-inch-538770251?gclid=Cj0KCQiA2ZCOBhDiARIsAMRfv9LR2NMqmpLHzd3d5ms8Mr41MHhGYtO2mNQkjn8y8rlA-JgVHUD78dgaAgo4EALw_wcB
40% off on first order
or
https://www.eurocarparts.com/p/amtech-oil-filter-wrench-with-strap-553774870?gclid=Cj0KCQiA2ZCOBhDiARIsAMRfv9KHrpQnvldSgboSKjiLogQsp1Z8O_C0pywfd8TC-ED6LXhVVxgrNvUaAqlqEALw_wcB
which uses sockets
as for the reassembly, a wooden broom handle tapered down has been known to work, for many years
Title: Re: Oil leak at front wheel
Post by: Phil C on 23 December, 2021, 20:56:14
Thanks Chaz, but I don't think I'll be attempting it this side of new year, esp as I've just this week moved house and am still getting things sorted.   Phil
Title: Re: Oil leak at front wheel
Post by: Phil C on 28 December, 2021, 14:45:05
Anyone who has no patience for stupid questions, please look away now.

To strip down my forks, in order to check them over and service them, do I need to remove them from the bike (in which case I guess I would need to disconnect the wiring and cables etc), or is it possible to leave the forks on the bike and strip the innards out? The forks (see pics) are, I think, the Heavyweight type.  Bike is 1965 B40F. Phil
Title: Re: Oil leak at front wheel
Post by: chaz on 28 December, 2021, 15:36:16
normally, loosen the top clamp bolt, loosen the top chrome nut, remove the front wheel and loosen the bottom clamp. the leg should then drop out.
only do the one side and you will not have trouble lining it all back up. service, then reassemble leg into yokes tighten up then you can do the other side . finally re insert the wheel.

take them both out together and you have fun re lining and threading everything back again.
unless. you intend checking the head bearings.

should be re looking at mine this week, sprang a leak from the drain screw and damn bike has not been on the road ,or even off the ramp yet¨¨
Title: Re: Oil leak at front wheel
Post by: AdrianS on 29 December, 2021, 09:51:13
You can remove them both together but put them back individually.
To remove in one piece and then strip for dismantling, just remove the brake cable from the cam lever, slacken off the clamp bolts at the bottom of the trousers, loosen the chrome top nuts a few turns then tap them with a mallet and the forks should drop a little. Then remove the chrome nuts so the forks can drop. Support the wheel when doing this to avoid too much strain on the chrome nuts. You will have to put the centre stand on some blocks of wood to give enough clearance to remove the forks.
Alternatively, remove brake cable, from wheel, remove mudguard, loosen of clamp bolts and remove each leg individually. There is a special too to screw into the fork leg if it is very tight in the yokes so you can hit with a hammer. This tool also helps reinstallation but the job can be done without it.
As previously said it is a simple fork and relatively easy to service but can be a bit messy!
They are quite a crude fork with not many components. Unless you can feel a lot of play in the fork legs on the bike, the bushes should be fine. Iíve never had to replace fork bushes but am sure others have.
You just need a couple of oil seals, a bit of string, possibly some PTFE tape and some new oil. I use 10/40 oil which I find fine but agains you will get advice to use different grades.
Title: Re: Oil leak at front wheel
Post by: Phil C on 29 December, 2021, 12:12:20
The string I guess is to act as an oil seal. What kind of string?
Title: Re: Oil leak at front wheel
Post by: JulianS on 29 December, 2021, 13:27:13
The string is used in the recess - indicated with screw driver in photo - below the threaded area of the fork bottom. BSA said number 5 twine. Good luck with finding that. You could use any suitable size string.

I use a length of PTFE tape twisted from flat into a thread - also a concentric carb O ring can be stretched over the thread and seated in the recess if you prefer.
Title: Re: Oil leak at front wheel
Post by: JulianS on 29 December, 2021, 13:44:49
BSA fitted the same basic heavyweight forks from 1945 - 1965, varying in mudguard and wheel fitting and fork shaft lengths. The below is from the B31/33 Instruction manual and describes how to remove and dismantle.

I suggest that the battery is disconnected and that the headlamp unit be removed from the nacelle.

Make sure that you safely raise the front of the bike as you would have done when you removed the front wheel to do the brake some time back.

The fork shaft can be a tight fit in the top yoke taper and can also be difficult to pull through the bottom yoke especially if the shaft is rusted and/or dirty. You can very carefully use a wedge in the split in the bottom yoke to open it slightly - not too far or it may fracture. A spray of WD40 can help.

With the fork leg removed the oil seal holder can sometimes be very tightly screwed on and if this is the case the proper tool is needed.

If you replace the oil seal the easy way to fit it in the seal holder is to push it in with thumbs as far as you can the screw the holder onto the fork bottom (before you assemble the leg) and this wil push it all the way in.
Title: Re: Oil leak at front wheel
Post by: Phil C on 22 April, 2022, 17:42:31
Just to wind this up: after removing the forks, stripping and checking them, renewing the oil seals, checking the brake over, and putting it all back together again, the leak hasn't recurred. So although I'm not absolutely sure where the leak was, I've serviced the forks, had fun, learnt a lot, and - hopefully - cured the problem. Many thanks again to all those who answered my many questions. Phil