Author Topic: What is this???  (Read 1163 times)

Offline jachenbach

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What is this???
« on: 15.12. 2014 19:51 »
Apparently some PO put an extra hole in this left engine case, and I'm trying to figure out why. It opens into a passage that then passes through a spigot to the right case, which then opens into the breather passage. The hole was plugged with a screw shown in the picture. Anyone know why this would have been done?

Online RichardL

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Re: What is this???
« Reply #1 on: 15.12. 2014 19:58 »
This  the actual breather hole for the crankcase. It puffs  air (I think, a balance of in and out)according to the timing of the rotating breather. You need to take out the bolt. Also, there might have been a pipe in it at one time (part number 67-922), but I think few of our bikes have that pipe.

Richard L.
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Online trevinoz

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Re: What is this???
« Reply #2 on: 15.12. 2014 20:10 »
And if you leave it there you will have many oil leaks due to high crankcase pressure.

Online RichardL

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Re: What is this???
« Reply #3 on: 15.12. 2014 21:41 »

The bolt, he means.
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Offline duTch

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Re: What is this???
« Reply #4 on: 15.12. 2014 21:54 »

  First thought is to stop oil coming out. ... *smile*
 Dodgy, but maybe the bolt was put there if the bike was put out of service, to keep mud wasps from building in there. ... Not recommended though, a bit of pipe as Richard said would be better, I've added a length of clear tube to run into a bottle(when I find one suitable)
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Offline jachenbach

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Re: What is this???
« Reply #5 on: 16.12. 2014 04:57 »
So if I understand correctly, the hole was factory made and the bolt added by someone. I looked at my other engine and didn't see the hole, so I thought the hole was an owner addition. I'll have to take another look. It did puzzle me trying to figure out how the engine could breath without an exit. It will be interesting to see the differences when I take the other engine apart.

Offline Topdad

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Re: What is this???
« Reply #6 on: 16.12. 2014 13:04 »
Dutch, for a supply of small bottles try your friendly pharmacist ,I nick ..er borrow, all sorts from my lads place , great for small amounts ,I have 2 for the forks (great for balancing the amount ) and another for the gearbox  which I fill and have on the shelf when I'm about to drain it ,gearbox that is not the shelf !!  but you could hook up a small bottle that wouldn't be to standoutty ,  *beer* Bob
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Offline Greybeard

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Re: What is this???
« Reply #7 on: 16.12. 2014 14:36 »
That's Kwality workmanship; with a capital K!

Online bsa-bill

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Re: What is this???
« Reply #8 on: 16.12. 2014 16:34 »
it's an interesting thread (not this one but the one on the screw in the photo) and the head of the bolt/stud is reminiscent of what we used to call "tech screw" when we fastened down profile sheets on roofs
All the best - Bill
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Offline Greybeard

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Re: What is this???
« Reply #9 on: 16.12. 2014 17:33 »
it's an interesting thread (not this one but the one on the screw in the photo) and the head of the bolt/stud is reminiscent of what we used to call "tech screw" when we fastened down profile sheets on roofs

The thread is similar to the screws that hold down the floor panels on an old Land Rover. They have a spring steel 'U' shaped clip that fits over a steel bracket and acts as the nut.

Offline jachenbach

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Re: What is this???
« Reply #10 on: 17.12. 2014 00:39 »
Well, duh.... I took a better look at the other engine and yup, it has the breather hole, just no screw plugging it. Probably should have taken it out of the box to look.  It is an odd screw. I don't recognize the thread at all.

Offline duTch

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Re: What is this???
« Reply #11 on: 17.12. 2014 01:16 »

  It also looks a bit like a screw from a hose clamp....?

 Yo Bob I have a small collection, but nothing yet that is 'just right' , and I also keep forgetting. ..!
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Online BSA_54A10

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Re: What is this???
« Reply #12 on: 25.12. 2014 06:58 »
Actually it is a self drilling masonary bolt and it looks like a little masonry ws left in the thread roots.

It is very common.
Clowns witn no understanding of the oiling / breathing systems buy a BSA, find oil leaking from this hole so they plug it up.
then they spend endles hours trying to fix all of the oil leaks from thsi " Pile of Pommie Shit " and finally sell it and go back to trying to look cool on a Honda.
I have found untold numbers of bike, particularly A 65's with the breather blocked off.
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Offline Rocket Racer

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Re: What is this???
« Reply #13 on: 27.12. 2014 06:56 »
I've tapped this hole on my race bike and put a fitting on it so I can run a hose off it and feed it to a catch bottle via a filter.
On a road bike this wouldnt be necessary. The breather timing is set on the cam end where a flanged tube with two holes permits limited breathing to reduce crankcase pressure.  I recall cake street classics recommend extending the holes to extend the breathing.
I also run bunn breathers but thats another story.
For road use just take out the bolt.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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