After a recent discussion on petcocks on this forum http://www.hondaspree.net/phpBB3/viewto ... =3&t=10107 I realized that I had made some assumptions about the inner workings of the fuel petcock valve. I decided to open one up to confirm how it operates, as this may help those brave few who attempt to get a stuck or debris-filled one working again.
Here is what it looks like cut apart.
The diaphragm is supported by a plastic disc and held in place by a nipple molded into the diaphragm.
The diaphragm itself acts as the valve, making a seal against the case top with a lip.
Here is a diagram for better visualization. If you have a stuck valve you can see where its possible to press the lip region of the diaphragm with a blunt instrument to assist in releasing it (as suggested by noiseguy in the tech docs section).
Interestingly, there appears to be a secondary rubber diaphragm valve just above the vacuum inlet. I surmise that this is present to prevent fuel from draining into the vacuum line in the event that the main diaphragm becomes punctured.
Anatomy of a Petcock
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Anatomy of a Petcock
Lambretta TV-175 (wish I'd never sold it!)
2005 Vento Phantom R4i 125cc (stolen)
1986 Yamaha XC180 Riva
1985 Honda CH150D Elite
1988 Honda SA50 LX Elite
1989 Honda SB50
2007 iScooter 150cc
2006 Roketa 150cc
2006 TNG Venice 50cc
2005 Vento Phantom R4i 125cc (stolen)
1986 Yamaha XC180 Riva
1985 Honda CH150D Elite
1988 Honda SA50 LX Elite
1989 Honda SB50
2007 iScooter 150cc
2006 Roketa 150cc
2006 TNG Venice 50cc
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- Veteran OG
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- Location: North of Seattle, WA
Re: Anatomy of a Petcock
Clivester - nice work, this will be helpful many a time in the future:)
Re: Anatomy of a Petcock
Good job.Nice pics,that does make it easier to understand.Thanks,Carp
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and they all need lots of love !!!
'78 ranchero,'77 pinto wagon,'64 t bird,'48 ford tudor,'31 ford furdor
and they all need lots of love !!!