Oil leak(s) b50

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b50whisperer
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Oil leak(s) b50

Post by b50whisperer » Tue Aug 18, 2020 9:26 am

I searched but came up blank, yet i have a vague recollection that this problem has been discussed. The b50 is leaking oil from the large engine barrel studs/ bolts adjacent to the sparking plug. I would like to effect a fix whilst the cylinder head is off, does anyone have intel or personal experience regarding this problem? Any insights much appreciated, thanks.

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Re: Oil leak(s) b50

Post by BSA_WM20 » Tue Aug 18, 2020 9:44 am

The usual fix is to put a slight countersink in the crankcase around the stud then an O ring to seal off the stud
It is crankcase fume being forced up the bolt hole.
If your name is Rex Bunn you now spend 5 years researching breathing and design a new crankcase breather system
Bike Beesa
Trevor

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Re: Oil leak(s) b50

Post by Barry Creary » Tue Aug 18, 2020 10:01 am

I still have a Rex Bunn on my B50 with no leaking I wonder how Rex is going haven’t seen anything from him for a while.

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Re: Oil leak(s) b50

Post by b50whisperer » Tue Aug 18, 2020 12:17 pm

BSA_WM20 wrote:
Tue Aug 18, 2020 9:44 am
The usual fix is to put a slight countersink in the crankcase around the stud then an O ring to seal off the stud
It is crankcase fume being forced up the bolt hole.
if the oil is able to penetrate the stud at the crankcase would it be able to also do so at the cylinder head gasket defeating the "O" ring solution.?
Because this is oil leak not fume/mist. Apologies if i am showing basic ignorance of mechanical engineering, here.
Is gasket seal recommended for the copper head gasket?

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Re: Oil leak(s) b50

Post by BSA_WM20 » Thu Aug 20, 2020 9:37 am

The O ring goes on the crankcase mouth
Oil passes around the threads up the hole in the barrel for the stud to pass through then out from under the head bolts totally bypassing any gasket.
You can spotface the head if you like and put a copper washer under the steel one and replace the nut with an acorn one but it is a lot more work.
It is not as common with B50's as it is with B44's
It is not the head gasket leaking .
Bike Beesa
Trevor

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Re: Oil leak(s) b50

Post by BSA_WM20 » Thu Aug 20, 2020 9:41 am

Barry Creary wrote:
Tue Aug 18, 2020 10:01 am
I still have a Rex Bunn on my B50 with no leaking I wonder how Rex is going haven’t seen anything from him for a while.
He has given up motorcycling all together and ended up selling all of his surplus stuff to Stuart Penhall .
Stuarts son has been selling the cashe off on evilbay for a long while.

Rex did a couple of documentries about NZ but his wife requires a lot of care
When they retured to NZ for good they were involved in a bad collision as they left the airport & Jenny never fully recovered.

The Bunn Breather busness is for sale if you have some spare time & cash
Bike Beesa
Trevor

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Re: Oil leak(s) b50

Post by Barry Creary » Thu Aug 20, 2020 10:22 pm

Trevor I’ve had a search on eBay for bunn breather with no results do you have a link.

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Re: Oil leak(s) b50

Post by b50whisperer » Fri Aug 21, 2020 6:23 am

BSA_WM20 wrote:
Thu Aug 20, 2020 9:37 am
The O ring goes on the crankcase mouth
Oil passes around the threads up the hole in the barrel for the stud to pass through then out from under the head bolts totally bypassing any gasket.
You can spotface the head if you like and put a copper washer under the steel one and replace the nut with an acorn one but it is a lot more work.
It is not as common with B50's as it is with B44's
It is not the head gasket leaking .
i appreciate your informative reply, Trevor. I will do the "O" ring mod and see how it works out. Thanks.
Art

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Re: Oil leak(s) b50

Post by Jeff K » Fri Aug 21, 2020 3:07 pm

I would think that using Loctite blue would serve the same purpose. Seals and locks, and can be remove with hand tools.
https://www.amazon.com/Loctite-Heavy-Du ... B000I1RSNS
Jeff

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Re: Oil leak(s) b50

Post by BSA_WM20 » Sun Aug 23, 2020 10:29 am

Barry Creary wrote:
Thu Aug 20, 2020 10:22 pm
Trevor I’ve had a search on eBay for bunn breather with no results do you have a link.
Rex did a batch about 5 years ago and has not made another as he is no longer interested in motorcycling.
The company was Carrel industries from memory
If you want to buy the business from him then his address is rexbunn
And he is with bigpond.au
Bike Beesa
Trevor

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Re: Oil leak(s) b50

Post by Momus » Sun Aug 23, 2020 4:56 pm

Any decent engine builder would be duty bound to use a sealant on those studs.

Spiral leakage is 101 stuff.
If you love it, lube it.

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Re: Oil leak(s) b50

Post by b50whisperer » Mon Aug 24, 2020 9:01 am

Jeff K wrote:
Fri Aug 21, 2020 3:07 pm
I would think that using Loctite blue would serve the same purpose. Seals and locks, and can be remove with hand tools.
https://www.amazon.com/Loctite-Heavy-Du ... B000I1RSNS
Jeff
good advice, thanks
Art

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