anyone run their bike without the vent t's successfully?

If it's broken or just needs tweaked

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juntjoo
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Joined: Fri Nov 10, 2017 6:19 pm

anyone run their bike without the vent t's successfully?

Postby juntjoo » Fri Jan 12, 2018 1:54 pm

reason I'm asking is because I've read mixed info, one person saying no t's caused bowls to overflow, where another said they were only for emissions and wouldn't affect operation, and I'm about to put my carbs back together and have fabricated replacement t's that doubt are 100% air tight(piece of fuel tube thru a barbed banjo t). Thanks
82" cb650 Nighthawk

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Folsoml
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Re: anyone run their bike without the vent t's successfully?

Postby Folsoml » Fri Jan 12, 2018 5:57 pm

If anything, the lack of the T's would KEEP the bowls from filling--not cause them to overflow. They do not need to be airtight. A more experienced person than me once said, "If the part was not needed, Honda would not have wasted money putting it on there."
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juntjoo
Posts: 247
Joined: Fri Nov 10, 2017 6:19 pm

Re: anyone run their bike without the vent t's successfully?

Postby juntjoo » Fri Jan 12, 2018 9:08 pm

Folsoml wrote:If anything, the lack of the T's would KEEP the bowls from filling--not cause them to overflow. They do not need to be airtight. A more experienced person than me once said, "If the part was not needed, Honda would not have wasted money putting it on there."


thanks. there's always optional parts too. speaking of which, I'm putting the vacuum petcock on despite what I've read, that nobody wants it and it causes a bunch of problems but I don't want to always have to close the other petcock all the time. curious, what does stopping the fuel at the carbs do anyway? Wouldn't there be fuel in the carbs anyway? And what symptoms do you get when these go faulty?
82" cb650 Nighthawk

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Folsoml
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Re: anyone run their bike without the vent t's successfully?

Postby Folsoml » Sat Jan 13, 2018 10:16 am

The way it works is the valve is normally closed (a more accurate name for this would be a "vacuum allow flow" rather than "vacuum shutoff"). When you crank the bike, the vacuum pressure created by the compression of the engine opens the valve--allowing fuel to flow to the carb. When the bike is shut off, the vacuum stops (obviously) and the valve closes. When they stop working--often when the bike has been sitting for a while--the ethanol in the fuel gums up the valve an sticks it closed. Another way these things can be a pain in the ass is when (again) the bike has sat up and the fuel in the bowls evaporates. It can require a LOT of cranking to finally get enough fuel in the bowls for the bike to start.

I've always removed them because the people from whom I learned to work on bikes always recommended it. It's not that hard to get into the habit of shutting off the petcock any more than it is to get in the habit of putting the kick stand down. I've sometimes forgotten to turn it off. Fortunately for me the float needles did their job. I've also forgotten to turn it back on, which sometimes has lead to an embarrassing situation at a stop light. :oops:
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juntjoo
Posts: 247
Joined: Fri Nov 10, 2017 6:19 pm

Re: anyone run their bike without the vent t's successfully?

Postby juntjoo » Sat Jan 13, 2018 11:59 am

Folsoml wrote:The way it works is the valve is normally closed (a more accurate name for this would be a "vacuum allow flow" rather than "vacuum shutoff"). When you crank the bike, the vacuum pressure created by the compression of the engine opens the valve--allowing fuel to flow to the carb. When the bike is shut off, the vacuum stops (obviously) and the valve closes. When they stop working--often when the bike has been sitting for a while--the ethanol in the fuel gums up the valve an sticks it closed. Another way these things can be a pain in the ass is when (again) the bike has sat up and the fuel in the bowls evaporates. It can require a LOT of cranking to finally get enough fuel in the bowls for the bike to start.

I've always removed them because the people from whom I learned to work on bikes always recommended it. It's not that hard to get into the habit of shutting off the petcock any more than it is to get in the habit of putting the kick stand down. I've sometimes forgotten to turn it off. Fortunately for me the float needles did their job. I've also forgotten to turn it back on, which sometimes has lead to an embarrassing situation at a stop light. :oops:


lol, good info. But WHY? Why stop it there if fuel will be behind it from last run anyway? I guess it's just a safety damn for when a float valve fails? That must be it, plus the convenience of not having to remember to shut it off yourself. So... it must be that float valve aren't made to live long under fuel pressure under atmospheric pressure? Do we turn off our petcocks so we don't have to change our float valves as often? If that's the case maybe it's worth changing those out as easy as it is to access them to avoid the responsibility (i loath responsibility) operating the switch.

Well if I keep it, with my new bright red calipers I'll need other parts to match so I'll probably paint this pcock red and if /when it fails it will have had this ugly chipping red paint anyway
82" cb650 Nighthawk


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