The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: madsens on 24.04. 2013 10:36
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Hi Guys
During a happy weekend driving in northern Germany with 9 more BSA's I have developed a rather big oil leak, partly coming from the rocker box, and I will be replacing the paper gasket with a copper gasket I just got from USA - But something worse happened *doh*- when trying to locate the oil leak I found out that one of the base cylinder nuts was impossible to put any torque on, it just keeps rotating, both nut and stud rotates, so I guess the thread in the case has ripped.
I haven't dismantled anything yet - but if my assumption is correct, what to do? Can it be fixed with a helicoil or similar, or will this not hold?
Any advise is most welcome, please
Kind regards
Joergen
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G'day Joergen, a helicoil will work, I have 4 in mine. Bummer the top end has to come off.
Remember whenever you touch the base nuts you need to reset the tappets.
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I think this not uncommon, on mine i had to get a extra long stud made up as well, as the top part of the hole in the case had been stripped more than once!
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Begs the question: If doing one helicoil here, should all be done? Leading to the next question: Has any machinist here made a jig for drilling all the cylinder base helicoil tapping holes while using a hand-held drill motor?
Richard L.
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Hi manusound i personally would only fix the stripped threads, i.m not sure why they strip maybe over tightenig, maybe wear, its not uncommon for the studs to screw out of the case when the barrel is removed, and so they get worn, not surprising given its not really possible to screw them in tight in the case as they do not bottom out, i use a stronger loctite on the case end (whit) of the studs compared to the nut (cycle) end...if you see what i mean! This in an attempt to make the studs stay in th case when the barrel is removed....
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Did all the studs on my head after two stripped, examining them (all) it looked like at some time maybe they'd had a wrong tap put down them.
So I did two, only to find another one stripped as I fitted the head so grasped the nettle and did them all, drilling them out is not a big problem with a bench stand, tricky bit is getting the tap to go down square, only one got off the vertical a bit but not enough to be a problem after a bit of round file manicure on the hole in the head - I hear the groans guys but it saved the cost of a set of barrels
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Hi guys
Thanks for all replies - helicoil it will be then - next question, can the drilling be done without taking the engine out of frame (hand drilling?) just with top and barrel dismantled? Or do I need to go all in and take the engine out of the frame to do the drilling *work* ?
Regards
Joergen
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Could be done in frame with care.
Make a jig to ensure the drill and tap go in square. A piece of 3" x 1/4" flat bar, long enough to straddle the case opening, with a 2" x 2" x 1 1/2" thick block tacked towards one end. Drill through block & bar in a drill press (square) for tapping drill size and another for the tap.
Cheers
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Hi all
After a busy weekend with a Confirmation (my youngest son) I finally got the time to rip the BSA apart to look at the damages.
And as always some good and some bad news... the thread was not ripped, but instead the stud was broken, so no new thread and helicoil needed this time.
But as you can see from the next pictures I've been driving with a broken ring on the left piston, so I guess that explains the blue smoke from the left pot?
The discoloring of the pistons - is that due to blow by, or something to be worried about? there are no marks to be seen or felt in the cylinder walls.
And finally please take a look at the picture of cam followers, they look pretty worn to me, but being in no way a mecanical genius, like some of you, I would like your opinion - do they need replacement/repair?
regards
Joergen
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2Fi1127.photobucket.com%2Falbums%2Fl635%2FJoergen_Madsen%2FBroken%2520ring%2Fth_Brokenring2.jpg&hash=b1854455da227546b31f480fa1d621a893e0e848) (http://s1127.photobucket.com/user/Joergen_Madsen/media/Broken%20ring/Brokenring2.jpg.html)
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2Fi1127.photobucket.com%2Falbums%2Fl635%2FJoergen_Madsen%2FBroken%2520ring%2Fth_Brokenring.jpg&hash=e7ce9e618bdfb1ecc7391b2e1668e5648501d6c0) (http://s1127.photobucket.com/user/Joergen_Madsen/media/Broken%20ring/Brokenring.jpg.html)
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2Fi1127.photobucket.com%2Falbums%2Fl635%2FJoergen_Madsen%2FBroken%2520ring%2Fth_Brokenstud.jpg&hash=19e49f1d47d8dedcccdff1733d75df8ed81d1925) (http://s1127.photobucket.com/user/Joergen_Madsen/media/Broken%20ring/Brokenstud.jpg.html)
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2Fi1127.photobucket.com%2Falbums%2Fl635%2FJoergen_Madsen%2FBroken%2520ring%2Fth_camfollowers.jpg&hash=932ce362107664a84548dd44ca12026a3faa3628) (http://s1127.photobucket.com/user/Joergen_Madsen/media/Broken%20ring/camfollowers.jpg.html)
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Yep that is blow by,and pretty excessive at that
The rings have not bedded in properly on either piston.
The left piston is now a paper weight.
The cam followers are through the case hardening so they need to be ground then cased .
have a really close look at the cam.
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As above.
The stud is an easy one. Usually the break flush or just below the surface.
I'd be very surprised if the bore isn't toast with a ring break like that!!
Bugga.
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Thanks Trevor and Muskrat for replies
Well I was afraid the replies would be something like that *sad2* ... But as said before "Shit happens".. so I'll be off to sea for a couple of weeks, trying to get som gulddust together for the repair and then I will transport the bike to the repairshop... this is out of my league, so I will have to call for help *help* in fact already have made arrangements with some guys not to far away - I'll have to stick to the bicycle for some time then...
Thanks anyways - thats life with an old BSA.
regards
Joergen
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Get the cam & followers done.
Do the rest your self.
When you refit the new pistons DO NOT THE RINGS OR THE BORE,
Wipe a little assembly lube on the bottom of the skirts the wipe it off,
Assemble the engine.
Put the cheapest supermarket oil you can fine in the oil tank ( or running in oil if you find the gold dust )
put your riding gear on
start the bike.
Do not let the engine idle
Go strait out on the road roll your hand up & down on the throttle with your foot lightly pressing on the rear brake.
The rings will be beded in in 20 meters
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Thanks again guys
One more question - hope I can explain:
When I grab the conrods they can be moved a bit sideways (they can wiggle a bit left and right), is that acceptable, or is there no "play" allowed there? hope you understand the question... if no play allowed I will have to take the bottom apart as well I suppose...
regards
Joergen
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G'day Joergen.
Yes they have side to side up to 0.024". A little rock (like a pendulum) is usual, bot NO up and down should be felt at all, unless you can feel 0.002" by hand.
Cheers
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Thanks Muskrat
I'm in the clear on that one then, so I will get cylinder, pistons and top checked/fixed - if I get the cam followers refurbished, will I have to do the cam as well? I would love to be on the road again in a not to distant future... I'm one of the few with only 1 bike -- and the riding season in DK is not that long (Wish I were back in Warren NSW) *smile*
regards
Joergen
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Depends on how worn the cam is. You could throw new (recond) followers in but watch your tappet clearances, they will open up quicker than normal. Maybe a job for next winter.
"(Wish I were back in Warren NSW) smile" The land of square tyres. At least where you are now you use all the tread.
Cheers
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Finally back ashore from my sea job - and out to the shed.
I now got the pistons off, and found one smal end bush totally loose, could turn freely and be pushed out with a finger - the other gudgeon pin bush was not loose, but had turned so the oil holes were no longer lined up. *sad2*
Could this be the reason for things to go wrong (broken ring) ?
Can new bushes be pressed in without dismantling the bottom part? or will I have to go all the way?
Is this a straightforward job, or will I need some outside help, as I guess the conrods needs to be heated and then the bush pressed in and reamed to the gudgeon pin size -
I'm a bookkeeper/paperpusher by trade *red*, so not very technically minded.... or equipped
regards
Joergen
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A job best given to someone with a tad more experience Joergen.
Could be done in the bike BUT.
You will need oversize bushes made, pressed in and reamed to size. The best way to do this is with rods out for accuracy and in line with the big ends.
Yes it wouldn't help with the ring problem, but could have been much, much worse.
Cheers
Looking back through the topic I'd say it's time for a rebuild anyway.