A7 Oil leak

[BSA500]

Hi all,
 I have an oil leak on my A7(surprise).I know exactly where from but I am looking for some ideas on a temp fix due to the work involved.The oil leaks past the bottom large screw that secures the primary cases into the crankcase.The reason is a worn thread(which is a helicoiled fix anyway) and when the bike is parked on its sidestand drops alot of oil.To fix would involve a complete strip down and I am not keen to do at the moment(its cold and I am enjoying riding it).I have tried ptfe tape wound over the screw threads but it doesn't seem to help much any ideas please.
Andy

[groily]

Hi Andy, I don't reckon there is a really good easy fix if it's that knackered - but you might try a stud and nut instead of the screw? If you are going to redo the thread when the motor's next apart, it wouldn't matter too much if you stuck a stud well and truly in with a good dose of loctite? Then, a close-fitting fibre washer (or even an O ring) over the threaded bit that sticks out (if you have to thread it on with some finger power so much the better), some silicon gunge, then a plain washer, then a nut with loctite (it mustn't fall off natch). If you leave the stud to set for a while you ought to be able to do the nut up reasonably tight. .  . but the whole thing can't stick out too far, for fear of fouling sprocket or chain or whatever. 
If it leaks on the sidestand with the engine stationary, there'll be a biggish amount of oil ending up in the primary drive I imagine? To resist the pressure of the pistons descending, the hole does need to be well closed.
Failing the above bodge, I reckon the only answer is the unavoidable but there are a million good ideas a minute here and someone might have a cracker. Groily.

[BSA500]

No oil ends up in the primary case as it leaks down the screw through the holes in the cases to the outside world.The stud should not foul as it passes through the cases and is not open to the inside workings its worth a think but anymore suggestions would be good.
thanks so far Andy

[groily]

course you're right Andy - was thinking momentarily of another marque - where the inner is separately held direct to crankcase with three screws - same principle but screws don't go through both cases. Whatever, makes a stud easier provided you can pack the nut with a spacer or turn up a one-off to nestle in the recess in the outer case- best of luck! Groily

[LJ.]

The screw in question shouldn't really be leaking unless the oil has been filling up quickly in the sump. Could there be high pressure in the crank case and the engine is not breathing properly causeing any oil around that area to be blown out?? The threads would have to be really bad for any oil to come out that way. I would have thought PTFE tape  would have been your answer but you say not. How about some PTFE and Araldite?? Other than that an oversize hex screw might help. Let us know how you get on.

[BSA500]

It doesn't leak much while I am riding only while its parked on the side stand so I think that suggests its not pressure related.Also when on the centre stand there is no leak.Thread is not great I can't put to much pressure on it while doing it up as does not feel good,that horrible about to strip feeling.I know it needs rehelicoiling but weather(dashed cold here old bean and under a carport ,no shed big enough),time and money prevent the proper fixing for now.I am sure the leak is not coming from around the chaincase to crankcase seal/gaskets and as an experiment I removed this screw while parked up(ok I forgot this could happen) and alot of oil came out.The stud way might be the best and involve less removal of bits until the proper fix but open to suggestions and lots of replies compared to many like forums its good to see.
Andy

[groily]

You're right it shouldn't LJ - but boy, when I was doing a trial run on my rebuilt gearbox recently with sprocket, clutch and chain attached, without primary cases or any screws in the 3 'oles, it amazed me how much oil came out and at what pressure - it was projectile stuff! More to do with pistons descending than intrinsic oil level I think. That lower screw hole in particular has to be well and truly plugged.
Having belatedly realised I wasn't on the AJ and Matchy site when I hit the keys a bit unhelpfully earlier (Alzheimers striking before Christmas this year!) and having been gently reminded how Beesas are screwed together, I remain of the view that these particular threads are sensitive little darlings. In my know-nothing world, into aluminium a stud beats a screw hands-down any day - where one can be fitted. Bespoke sleeve nuts over studs would be far better for the big three screws on the BSA chaincase IMHO.  Ref A-series sump-plate for example, blessed with studs for a good reason, even if they often come out with the nut owing to their miserable position.
Heresy, but my beast of the other marque had the same prob as BSA 500's - amplified by the fact that it filled the chaincase over time as the screws only hold the inner on - so guess where the oil goes?- and has been resolved pending next strip-down by loctited studs, washers and nuts in place of worn screws in the worn 'oles (- same general pattern of three). (Plus, in case anyone else here knows the AMC twin's foibles intimately, with an oil seal conversion over the drive-side mainshaft to try to keep the oil inboard of the main bearing).
Yes, if there is excess pressure in the A7's crankcase the leak will be worse, ditto if wet-sumping is filling things up all the time, but if there isn't an obvious other problem, and our friend reckons not, I really do reckon a well-attached stud and nut has a better chance than anything short of welding or blanking off the holes in the drive side crankcase. But in the end, the bullet might have to be bitten and the cases split to rectify the cause rather than treat the symptoms. Fingers crossed in this case - and here's to better ideas!. Groily

[bsa-bill]

I think LJ hit the nail on the head with this one. I would check engine breathing
Do you mean the helicoil is slack in the hole or the screw is slack in the hole
If the helicoil is slack take it out and replace with a new one useing loctite
If the screw is slack in the helicoil I would replace the helicoil and the screw, again with loctite
I am not at all happy with my understanding of breathing problems, I hear lots of folk blame the pistons for creating pressure as they descend, few if any take into consideration the piston ascending will surely create a lowering of pressure which should ( if ya canna change the laws of physics Jim ) negate to some extent the pressure build up when the come down again.
I'm probably missing something no doubt someone will put me right   
But many many people ride A7/10s without any breathing problems, as they say go figure

All the best - Bill

[LJ.]

Andy...

From what you describe in your last post, I would visualise that maybe your bike leans over too far on it's side stand, the engine probably wet sumps very fast and that you are using a rather thin viscosity oil (obviously thinner when engine is hot). All of which will find a way out of a badly fitting primary case screw, especially that large one at the bottom.

Remedy worth considering...

Stand bike up a bit more vertical on it's side stand, maybe a new one is called for, or experiment with a block of wood underneath the foot.
sort out wet sumping problem or at least investigate to see if it is doing so.
A nice thick monograde oil, this time of year 40 grade. ( A lot to be said for thick oils where leaks appear!)

This might help untill a proper fix is planned. Good luck.

[RichardL]

Andy,

If I have followed all of this correctly, the screw that is leaking is the primary case level indicator. Being that your bike is an A7, I am assuming you have a chain tensioner and the leaking screw is the one just forward of the tensioner. I also assume that the leaking oil is appearing on the outside of the primary cover, having leaked past the head of this screw. I suppose oil from within the crankcase can get pushed past the helicoil. It may not even require wet sumping, because the walls of the crankase are certainly fully soaked with oil when the engine is running. I think a little positve pressure within the crankcase would tend to push oil past most unsealed threads, not to mention loose ones. OK, fine, oil passes the threads and gets into the primary case. If its a lot, the level indicator screw is always submerged and more likely to leak if it is not well sealed beneath the head of the screw. Also, I assume there would be clutch problems. Even if it's not submerged, the level indicator screw needs to be well sealed.  My parts book shows a fiber washer under the screwhead for the level indicator and (in the case of later A10's the drains screw). You should take a very close look, with magnification, at the shoulder where the washer should seal (assuming you are using a washer). That shoulder should be flat and not chipped or nicked or otherwise damaged. I can easily imaging someone (not you, of course) puttng a split lock washer under the screw heads and causing a gouge. If it is damaged, a touchup with a piloted counterbore would correct that condition.

I also had a thought that a messed up helicoil job (like, leaving the tab on at the bottom) could give a false indication of seating of the screw. therefore leaving it unseated and leaking. you did mention that is had a bad feel when trying to tighten.

There is another thing worth mentioning about primary case indicator screws. But first, let me say that I only know this because I read it in Chilton's BSA Repair Guide. On early pre-unit "A" models, the level indicator was where I said, but on later models BSA decided that a lower oil level in the primary was better, so they moved the hole behind the chain tensioner. Chilton recommends cutting away the inside of the cover at the rearward location similar to the forward location.

Well, Gents, thats it from me for now. Feel free to dig in and let me know if I have erred.

Richard

[BSA500]

Should have stated this is the 1960 model with the combo drain level plug.The plug is set well back and the leak in def from the front lower screw.The bike does not wet sump( I know this because it used to quite badly and I should have taken the hint that all was not good with the oil pump but the seize up sort of told me-thats another story) because the pump has been reconned by SRM with a iron body.The side stand is a BSA one so it leans as far as it should(although it does seem a little steep) but at work there is no way of propping it up.Using 20-50 oil but really cannot afford sae 40 at the moment,so pricey and rare(you have to have it posted very expensive).The engine on this has always been a good 'beather' no issues with leaks due to pressure problems.I think oil should be treated like water,if there is any sort of weakness it will find a way in or in this case out.The stud is still looking favourite,and while we are on the subject of studs over screws/bolts I replaced the fork cap bolts with studs much easier to pop the front wheel in and out(captive spindle on the later A7).
Andy

[BSA500]

Update:I have found a really simple temp fix for this leak.High vacuum silicon grease as used in labs to put ground glass joints together.Smeared an amount on the threads screwed it in and no leak since.It is stable at over 100 deg so shouldn't melt off.