Author Topic: Ripped thread - cylinder stud  (Read 2027 times)

Offline madsens

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Ripped thread - cylinder stud
« on: 24.04. 2013 10:36 »
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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Re: Ripped thread - cylinder stud
« Reply #1 on: 24.04. 2013 10:51 »
 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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Online KiwiGF

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Re: Ripped thread - cylinder stud
« Reply #2 on: 24.04. 2013 12:55 »
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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Re: Ripped thread - cylinder stud
« Reply #3 on: 24.04. 2013 13:28 »
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?

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Re: Ripped thread - cylinder stud
« Reply #4 on: 24.04. 2013 13:37 »
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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1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

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Online bsa-bill

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Re: Ripped thread - cylinder stud
« Reply #5 on: 24.04. 2013 16:55 »
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
All the best - Bill
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Offline madsens

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Re: Ripped thread - cylinder stud
« Reply #6 on: 24.04. 2013 17:51 »
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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Re: Ripped thread - cylinder stud
« Reply #7 on: 24.04. 2013 21:01 »
 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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Offline madsens

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Re: Ripped thread - cylinder stud
« Reply #8 on: 30.04. 2013 11:36 »
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








BSA A10GF 1962
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Re: Ripped thread - cylinder stud
« Reply #9 on: 30.04. 2013 11:49 »
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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Trevor

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Re: Ripped thread - cylinder stud
« Reply #10 on: 30.04. 2013 12:42 »
 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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Offline madsens

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Re: Ripped thread - cylinder stud
« Reply #11 on: 30.04. 2013 13:14 »
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
BSA A10GF 1962
Denmark

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Re: Ripped thread - cylinder stud
« Reply #12 on: 01.05. 2013 10:12 »
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
Bike Beesa
Trevor

Offline madsens

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Re: Ripped thread - cylinder stud
« Reply #13 on: 02.05. 2013 18:07 »
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
BSA A10GF 1962
Denmark

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Re: Ripped thread - cylinder stud
« Reply #14 on: 02.05. 2013 21:28 »
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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