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b44 1970 shooting star
#438401 06/04/12 10:37 pm
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anybody know why oil appears on the fins of the barrel

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Re: b44 1970 shooting star
conhawks #438403 06/04/12 10:44 pm
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I'm interested in the answer as well because its the same on my 67 .... bottom 2 fins on the left side .... nowhere near any joints.

Re: b44 1970 shooting star
LarryLebel #438404 06/04/12 10:48 pm
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yep, same as me, interesting

Re: b44 1970 shooting star
conhawks #438436 06/05/12 1:01 am
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Its probably caused by one of several things as follows:-

- the rocker oil drain holes arent sealed properley at the head gasket and are leaking on to the fins
- oil may also be leaking from the rocker box joint, tappet covers or rocker feed.

Sometimes, oil leaks out from somewhere and finds its way to unexpected places, but my guess would be the head gasket seal.


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Re: b44 1970 shooting star
conhawks #438472 06/05/12 8:22 am
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There are 4 possible routes for oil from the barrel (plus the top end ones) head gasket joint, 2 small drain holes and the pushrod tunnel, any of these could have a porus section in the casting next to them allowing oil to seep out.

Re: b44 1970 shooting star
gunner #438476 06/05/12 8:40 am
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And to add to Gunners post.
On B44's oil can bypass the cylinder base gasket and enter the tunnels for the long barrel studs. Also the cases oft split down the mouth along the stud.
This space is not necessarily oil tight and oft leaks oil from under the head nuts.
From there the oil seems to "mystically" get itself into all sorts of weird places.
Excessive crankcase pressure makes this substantially worse and can pump a lot of oil out this way.
It was this problem that sent Rex Bunn into investigating the breathing on unit singles & the developement of his improved Bunn Breather.

The usual fix is to pull the barrels and the studs, slightly countersink the holes then fit a thin o ring.


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Re: b44 1970 shooting star
conhawks #438509 06/05/12 1:33 pm
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Yes, I had this on one of my round barrels, if you shine a torch in the second fin you can see that if oil got up the studs from the base joint, the second fin is the first chance it has to exit as the studs become visible at that point (not enclosed) & because models that have a prop stand on the left (my model was produced with no stand) will let the oil collect on the second fin on left side of engine.
I don't, & never have owned a square barrel B44 but I can only think the same applies, although I am aware the square barrel has some differences, one being bigger gaps between the fins which probably makes a wet fin even more noticeable than on a round barrel.

Last edited by pachy; 06/05/12 2:03 pm.
Re: b44 1970 shooting star
pachy #438544 06/05/12 5:45 pm
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Interesting. I for one am gonna have a look, its not place I would normally inspect.

Re: b44 1970 shooting star
conhawks #438572 06/05/12 6:59 pm
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The only way I've been able to positively identify leaks like this is to thoroughly degrease the engine and then let it idle....for a long time. If you ride it, it will blow the oil all over the place, sometimes up. If you still can't find the leak (I had a similar one on my Royal Star that revealed a cracked rocker box) try some dye and a black light. Works a treat!


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Re: b44 1970 shooting star
Alex #438682 06/06/12 3:38 am
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OK I see. The studs pass through holes in the fins and are not enclosed. The mystery is over. I have one of Brit Gaskets barrel gaskets, maybe they are not as good as they are touted to be.

Re: b44 1970 shooting star
LarryLebel #438702 06/06/12 7:03 am
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Quote
OK I see. The studs pass through holes in the fins and are not enclosed. The mystery is over. I have one of Brit Gaskets barrel gaskets, maybe they are not as good as they are touted to be.


Did you pull the barrel studs and dress the crank case before fitting the base gasket ?
You will find that the alloy creeps up to make a little nipple.
Also check very carefully the crank case mouth down the length of the studs with a dye penetrant kit.
Chances are that you will find a crack.


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Re: b44 1970 shooting star
BSA_WM20 #438791 06/06/12 4:37 pm
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No I did not dress the crank case working on the minimalist theory which I know is not a good idea. My bike is just a rider. One day I will do a complete restoration at which time oil leaks will not be tolerated.


Moderated by  Allan G, Jon W. Whitley 

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