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Carburetor Oil Disappears

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H

healeygal

Jedi Warrior
Offline
Where does the carburetor oil disappear to? I add it, it disappears...I add it, it disappears...

Could it have anything to do with the fact I only hand-tightened the plunger do-hickey (excuse the non-technical term) and one of them vibrated loose? The little domes they screw into are absolutely dry on top, and I don't feel anything leaking underneath. Carbs were completely dismantled and rebuilt five years ago by a professional mechanic. Time to do it again??

Sharon
BN1 on the road again
in spite of it's non-mechanically inclined owner
 
Hi Sharon,
Are you sure that there really IS a problem. If you remove the cap & look down inside you will see a smaller "inner" tube which is the damper. The carbs only need to be filled to within about 1/2" of the top of this inside tube. If they are filled higher than this, the excess oil will just be pushed out. It makes a bit of a mess inside but does no real harm.

You can operationally check the oil level by withdrawing the cap & piston & reinserting it. You should feel a bit more resistance when pushing the damper piston down than you feel when lifting it. It is a one way hydraulic action. If you feel the same resistance both ways, it means that the damper is truly low on fluid. If you had an air filter off, you could reach in & lift the piston with a finger tip. You should be able to feel the hydraulic resistance of the damper as you raise the piston. Compare this feel to how it feels with the cap & piston removed, no damping.

I believe that you have the H series SU carbs. There is no place for the oil to leak out, except the top if it is overfilled.
D
 
Hi Dave,

Back out to the garage again. I saw the oil level you're talking about, withdrew and replaced the piston, and could feel the resistance you explained. Feel like a real expert now. My thanks to the real expert! /ubbthreads/images/graemlins/savewave.gif

Sharon
 
I really do have this problem on my BJ8. Any ideas?

Thanks
Walter
 
Walter,
If your BJ8 has the HD8 carbs, the bottom of the damper tube should be sealed the same as Sharon's. There are some other SU models with spring biased needles that do have a possible leakage path between the oil chamber & the needle. You could try applying light air pressure, with a rubber cone air chuck, to the top of the tube, piston & needle submerged in water, & look for leaks.
D
 
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