How does the petcock work?
How does the petcock work?
Hello, amigos!
I finally ran through my full tank of gas putting 134 miles on WorshipCycle (about 34.5 mpg). I was sitting at a light and revved the engine a bit and noticed some "stumbly running" in the mid RPM range. I checked the choke - no, it was off - and thought, "Hmmm, I wonder if the machine is nearing the reserve?" I reached down, flipped the lever from full down to full up, and the bike immediately started running normally.
On the petcock, why would it work like this - why wouldn't it just cut the fuel off? Is the pipe set to suck some air into the line so you know you've got to switch to reserve?
BTW, how much fuel is in the reserve anyway?
I finally ran through my full tank of gas putting 134 miles on WorshipCycle (about 34.5 mpg). I was sitting at a light and revved the engine a bit and noticed some "stumbly running" in the mid RPM range. I checked the choke - no, it was off - and thought, "Hmmm, I wonder if the machine is nearing the reserve?" I reached down, flipped the lever from full down to full up, and the bike immediately started running normally.
On the petcock, why would it work like this - why wouldn't it just cut the fuel off? Is the pipe set to suck some air into the line so you know you've got to switch to reserve?
BTW, how much fuel is in the reserve anyway?
Retired Super Moderator - At large E=MC2
Joined: Feb 2011
Posts: 2,299
Likes: 4
From: Tulsa,OK
There is only one reservoir, your tank is not sub-divided.
You are just drawing from an intermediate level of the fuel on "main".
The petcock has a tube inside, pointing up.
Normally it draws from the top of the tube.
When the gas is drawn down below that point it starts to sputter.
As you accelerate or brake the gas moves forward or back in the tank.
This will slightly raise/lower the level of the gas at the point it draws from.
When you switch to "reserve", it draws from the very bottom of the tank.
Thus allowing you to empty that last .4-.6 gallon of gas.
Since that's where debris and contaminants will accumulate,
you should only run on reserve when absolutely needed.
Filling up and switching back to main, can help prevent fouling the carbs
with accummulated sediments (despite the fine-mesh screen, that surrounds the tube).
Ern
You are just drawing from an intermediate level of the fuel on "main".
The petcock has a tube inside, pointing up.
Normally it draws from the top of the tube.
When the gas is drawn down below that point it starts to sputter.
As you accelerate or brake the gas moves forward or back in the tank.
This will slightly raise/lower the level of the gas at the point it draws from.
When you switch to "reserve", it draws from the very bottom of the tank.
Thus allowing you to empty that last .4-.6 gallon of gas.
Since that's where debris and contaminants will accumulate,
you should only run on reserve when absolutely needed.
Filling up and switching back to main, can help prevent fouling the carbs
with accummulated sediments (despite the fine-mesh screen, that surrounds the tube).
Ern
Last edited by MadHattr059; Jan 19, 2013 at 04:56 AM.
Super Moderator
Joined: Aug 2006
Posts: 5,304
Likes: 512
From: South Florida, USA
MadHattr059 has an excellent description of how the Petcock works. I'm not as cautious though when it comes to riding while on reserve (call me a rebel, lol). The Petcock has a strainer on it for large particles, and you also have an inline fuel filter that's going to catch virtually everything else. Change the fuel filter every couple of years and you'll be fine. On our F3's, we'll comfortably ride 25 miles or so before being concerned about having to fill up. I start getting worried if I go beyond 30 miles. I know from experience that I can't go further than 36 miles while on reserve 
Thread
Thread Starter
Forum
Replies
Last Post
cbrboyze
How-To: Mechanical
7
Mar 5, 2009 08:47 AM
