The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: bsa-bill on 12.07. 2011 20:43

Title: Weevel
Post by: bsa-bill on 12.07. 2011 20:43
Got a funny one here, attempting to cure a leak around the rear of the crankcase, seems to be weeping out of the vertical join, wiped completely dry at night it's wet again in the morning, definitely coming out of the join.
OK got the barrels lifted of and had a look in the camshaft trough, almost empty, thought as much.
gently turning the engine over, notice what oil is in the trough getting pickud by the cams - good, then I spot a hole, perhaps an eighth big in the rear wall of the camshaft trough.
It looks quite smooth, shoved a small wire probe into it , it goes in a fair way.
Surely I would have noticed this hole before,(considering how familiar I am with the internals of this motor.
Any ideas folks - porous case maybe.
What about a cure, would some of that plastic metal work
Any chance this is one of those mods of days gone buy
how come I missed it - Should I go to spec savers
Title: Re: Weevel
Post by: muskrat on 12.07. 2011 22:38
Gee Bill that's a bugga. Sort of looks like an air hole in the casting. You could try an epoxy resin or liquid metal. The hole would need to be cleaned well with a carby/brake cleaner, I would use a couple of hot/cold cycles with the cleaner and comp air and heat gun. Also heat cases before applying the filler.
Good news is it could be done without any more dismantling.
Cheers
Title: Re: Weevel
Post by: trevinoz on 12.07. 2011 23:41
Bill,
             There is supposed to be a hole in the trough for the oil from the relief valve.
There is also another hole behind the timing gears.
I just had a look at a case and the hole looks like it's in the right place but a bit mangled, probably from someone probing it in the past.

     Trev.
Title: Re: Weevel
Post by: muskrat on 13.07. 2011 00:36
DOH, yep Trev is correct. Just had a look at my spare cases. The trough will empty to that level by way of draining to the hole behind the timing gears as Trev mentions.
So it's back to the case joint.
Cheers
Title: Re: Weevel
Post by: bsa-bill on 13.07. 2011 19:50
Yep - hang head in shame, I'd forgotten about that oil flow chart.

got the engine out just now, the cases split pretty easy probably due to the rear of the join being wet with oil, front's dry.
That hole is drilled right through the case, so it's blocked off by the drive side case right at the spot the oil leak was and it is of course pretty near the edge of the case.
I'm giving some thought as to how to safely blank it off, have to be careful.
Will put some goo between the joins this time, that black loctite seem good, I used it to seal the sump plate and when I removed it any that had squeezed out had set like rubber, hadn't gone hard at all and was not easy to pull off
Title: Re: Weevel
Post by: trevinoz on 13.07. 2011 22:22
Musky,
                Have another look at the oil circuit.
The oil from the relief valve travels thtough drillings in the case and lubricates the timing gears through the small hole and exits via the cam tunnel into the crankcase sump.

  Trev.
Title: Re: Weevel
Post by: muskrat on 13.07. 2011 22:37
I see that Trev, but when the motor is not running the oil in the trough would drain (seep) back to the timing gear hole, down to the level of the hole in the trough. It might take a while.
Cheers
Title: Re: Weevel
Post by: chaterlea25 on 13.07. 2011 23:13
I Bill,
I think that the hole on the face between the cases should be plugged??
I will check some spare cases tomorrow *idea*

HTH
John
Title: Re: Weevel
Post by: trevinoz on 14.07. 2011 02:35
No plug, just a threaded hole for a stud.
Maybe it is leaking past the threads?

  Trev.
Title: Re: Weevel
Post by: bsa-bill on 14.07. 2011 09:31
No plug in mine or thread either, looks possible there is the remains of a thread in the form of a slight shoulder just where the hole in the side is, could be from drilling through though.
not sure I want to re thread in case swarf gets down the oilway, I'm thinking maybe a nylon plug, heat the case and shrink it in, rubber would be good but might degrade in oil (degrade - the new word is deg according to F1).
Musky has the right scenario as it leaked more when the engine stopped, probably as the cases cooled
Title: Re: Weevel
Post by: a10gf on 14.07. 2011 10:22
Learned something (again). In the past did vaguely remark the presence of a hole, but now I see the whole, with oil channel and plug. In my case (plunger) there seems to be a brass insert pressed in at the case joint.
Title: Re: Weevel
Post by: chaterlea25 on 15.07. 2011 01:21
Hi Bill,
I stripped the crankcases today and the oilway is definitely blocked with an alloy plug
I have taken a couple of pics, will upload them tomorrow

HTH
John O R
Title: Re: Weevel
Post by: bsa-bill on 15.07. 2011 09:18
cheers John
Title: Re: Weevel
Post by: chaterlea25 on 15.07. 2011 22:11
Hi Bill,
Photo's attached
I hope this clarifies the issue  ????
Please note the copious white bathroom sealant in the first photo  *eek*
I'm starting a new thread on this engine

Regards
John O R
Title: Re: Weevel
Post by: bsa-bill on 15.07. 2011 22:54
Mine looks like that now John (well minus the bathroom sealer)
Used one of the missus's knitting needles, an alloy one ground down to slightly more than the diameter of the hole and shrunk in a tad further in than level so a bit of goo will seal it.

Looking forward to your new thread, I have an image of you motoring along in a shower cap
Title: Re: Weevel
Post by: muskrat on 15.07. 2011 23:02
Ha, that makes me want to poke out my minds eye. LOL
Title: Re: Weevel
Post by: trevinoz on 16.07. 2011 01:50
I should have put my specs on!
I had a look at a few cases and some have a plug and some not.
I wouldn't think that anyone had removed the missing plugs so it seems that it may have been a fix for a leakage problem by BSA.

  Trev.