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Does a diaphragm sit still or move vigorously in high speed operation?

Chainsaw Jim

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Rubber allow the most flow, blue plastic the least?
It isn't about the volume of flow, it's about the ability of the little valves to keep up with the impulse signal. Higher performance saws need a more responsive material.
I've seen conflicting information on which is the better performing material. One source says the tan woven one is the highest performance while another source claims the black rubber one is. I think the blue one is supposed to have a higher resistance to ethanol.
 

huskihl

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It isn't about the volume of flow, it's about the ability of the little valves to keep up with the impulse signal. Higher performance saws need a more responsive material.
I've seen conflicting information on which is the better performing material. One source says the tan woven one is the highest performance while another source claims the black rubber one is. I think the blue one is supposed to have a higher resistance to ethanol.
I've heard the tan one is most resistant to ethanol
 

chy_farm

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Yesterday this tool/unit got a prize at the Homemade Tools net, that is called
'Homemade Tool of the Week Winner'
http://www.homemadetools.net/forum/carburetor-diaphragm-movement-detector-its-system-67278

31-come-on.png
 

legdelimber

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I'd speculate that the stiffness and mass/weight of diaphragm material affects the high speed performance.
I can't speak to high speed results, but I'll say that the black rubber pump diaphragms make for a noticeably easier cranking saw or trimmer, etc.

I'll toss those black plastic diaphragms out of a brand new carb, IF I have the rubber one to replace it.
Just gotta make sure the operator never runs ethanol in the unit. The ethanol causes the flaps to pucker or wrinkle and there goes the sealing and easy starts!
This leaves you at the mercy of how sticky and viscous your fuel mix is, in order to get a sealing effect then.
Thus you get all of that extra rope yanking, with the choke on, in order to get the diaphragm wet and holding a seal, when doing a cold start.

Wish I could find (and afford) to squirrel a few away for all my various OPE items.
 
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