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threaded hole leaking
#802967 03/27/20 12:36 am
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I'm afraid to ask this because last time it required me to tear the engine down again blush but last night I liberally applied oil to the valve assembly before buttoning it up, knowing that it was just going to settle in the sump. Now I see a little oil coming out of a threaded hole underneath near the PRV. I can't remember what threads in there, the manual doesn't show anything (not that I see). Also, there's another threaded hole near the PRV... is this for the PRV pressure?

Here's a photo of what I'm talking about

Last edited by Danam; 03/27/20 12:37 am.
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Re: threaded hole leaking
Danam #802976 03/27/20 2:57 am
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Those holes are just plugs for the gallery drilling s, 1/8 bsp plugs fit them.
You can install the plugs with a little thread sealant or just some loctite 518.
I used to use the one by the oprv as a take-off for my end feeds when racing,
you can use it for a gauge if you wish, but it's a bit tight for space.

It looks like you've put it together without the plugs fitted...............

Last edited by NickL; 03/27/20 2:59 am.
Re: threaded hole leaking
Danam #802977 03/27/20 2:59 am
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Where you're leaking, on all mine that is a set screw/plug from the factory to plug an incidental drilling. I think. That second hole, I got no theory.

Re: threaded hole leaking
Danam #802979 03/27/20 3:02 am
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Nick always beats everybody. Is that second hole in all of em? Short memory here, but I do remember they're a little hard to get to without lifting the front of the engine.

Re: threaded hole leaking
Danam #802982 03/27/20 3:07 am
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The early motors had the plug by the oprv welded over then they used a small screw.
The type you have is a late one which had allen headed grub screws fitted.
The vertical one is the drilling from the vented oil from the relief valve back to the return line of the pump.
The other is the main pressure gallery, that will flood your floor when the bike is started and
run the bearings dry, both must be plugged or used..

Re: threaded hole leaking
Danam #802989 03/27/20 3:20 am
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Danam you better start shopping for another basket A65. You'll want use all this new knowledge.

Re: threaded hole leaking
Danam #802990 03/27/20 3:20 am
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I see, the machinist must have removed them and not replaced. I don’t see this part in any manual. Do you know what size I should use or where I can get these plugs?

Re: threaded hole leaking
leon bee #802991 03/27/20 3:21 am
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Danam Offline OP
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Originally Posted by leon bee
Danam you better start shopping for another basket A65. You'll want use all this new knowledge.

I’ll pay it forward to the next poor soul that needs help!😂

Re: threaded hole leaking
Danam #802995 03/27/20 3:32 am
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The plugs are 1/8 bsp.
Try SRM or BBB or anyone who may have some cases laying around.
One of the beezer stockists in the 'states must have some somewhere.

Re: threaded hole leaking
Danam #802996 03/27/20 3:35 am
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Re: threaded hole leaking
Danam #803001 03/27/20 4:18 am
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Brilliant, thanks Nick! These are easier to find than toilet paper right now!

Re: threaded hole leaking
Danam #803002 03/27/20 5:00 am
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On an early case without the raised number stamp pad A65L the holes are 1/4-26. The one under the OPRV connects the pump to the OPRV. The one behind connects the pickup tube to the return side of the pump.

Re: threaded hole leaking
Danam #803009 03/27/20 7:56 am
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I've just been working on a pre-64 engine it had a cheese head screw which was BA.
Looked original to me.

Re: threaded hole leaking
Danam #803031 03/27/20 2:07 pm
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Danam, knowing the size (1/8 bsp), you should be able to get what you need from British Tools and Fasteners (in Lyons, NY).


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: threaded hole leaking
Mark Z #803046 03/27/20 5:19 pm
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Danam Offline OP
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thanks, I just ordered them off amazon. the price was right. I'm going to need to unmount the motor (again!) to install them. How far do they screw in? Can I use sealant with them or is that an issue?

Re: threaded hole leaking
Danam #803050 03/27/20 5:54 pm
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I'm surprised to hear you ordered them from Amazon. Did you order them by size or by BSA part number? Who is the seller?

I can't envision a problem with using sealer or Loctite. Those plugs have been in both of my A65s for fifty years and have never been removed through many rebuilds. Just don't push sealant into the holes past the plugs.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: threaded hole leaking
Mark Z #803092 03/27/20 10:53 pm
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Originally Posted by Mark Z
I'm surprised to hear you ordered them from Amazon. Did you order them by size or by BSA part number? Who is the seller?



Mark,

NickL posted the Amazon link earlier in this thread.

https://www.amazon.com/Thread-Allen-Chrome-Plated-Brass/dp/B07DZ8CRKS


Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
1955 Tiger 100 - Project
1971 BSA A65 650 - Project
1972 Norton Commando 750 "Combat"

Re: threaded hole leaking
Danam #803101 03/27/20 11:24 pm
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The link i posted is for taper threaded type so they may not screw in more than 1/4 inch or so.
I think the originals were parallel thread.
Just don't go bananas tightening them, use a little thread seal or blue loctite and they'll be fine.

Re: threaded hole leaking
Danam #803111 03/28/20 12:20 am
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I see no obvious reason to assume the holes were taper threaded, as opposed to straight thread.
Straight thread is more likely, but I suppose taper is possible.
Even so, if the hole were straight thread, a taper plug should only match its max od to the id at its extreme when fully inserted.

A taper fitting would usually employ PTFE tape or sealant, whereas a parallel fitting would usually employ a sealing washer.
That's just usual hydraulic practice, BSA may not have followed this in such a low pressure environment.

Re: threaded hole leaking
Danam #803115 03/28/20 12:47 am
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Dave/Koan, From memory the holes are not tapered, beezer used to use a bit of welseal on the plugs.
The main gallery is at around 100psi when oil is cold and the pump is working properly so that one needs
to be a good seal.

Re: threaded hole leaking
Danam #803118 03/28/20 1:01 am
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Hi Nick, that's what I meant about a low pressure environment, easily within the capability of such assemblies! ie not like hydraulics.


Moderated by  Allan G, Jon W. Whitley 

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