Sorry folks a perennial question

[JohnT]

The Bing carburettor diaphragm. Is there any real advantage in using a genuine BMW part or is the half price Hydrin example just as good?
Other than actually having a hole in a diaphragm do they have a life span and is there a need to change them?

[Jeff in W.C.]

I heard/read that the thickness of the diaphragms can vary depression on the manufacturer, which can impact performance. I have no first knowledge of this. It’s just what I’ve read.

[Kurt in S.A.]

For my money, I would go with genuine parts. You're dealing with a critical element of getting fuel to the carb and it working correctly. Another member opted for something cheaper and the discussion was here:

viewtopic.php?t=12144

Kurt

[Rob Frankham]

I have used both types and not noticed any appreciable difference, after all, the only function of the diaphragm is to form a flexible seal between the piston and the carb body. It's possible that a thicker (less flexible) diaphragm might marginally affect throttle response but I haven't noticed it. In my opinion, even the ones supplied by BMW are not the same as those originally supplied...

And, yes, they do have a life although failure is normally due to a hole so it's a moot point... however, the flexibility does change over time so it is generally recommended they are both changed at the same time... even if one is visibly good.

Rob