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Petcock, who do I believe?

7K views 37 replies 28 participants last post by  agro 
#1 ·
While reading my new Bonnie's manual, I noticed the instructions are to turn the fuel petcock to OFF when not riding, which is what I used to do back in "the day" with older bikes. However, when I picked it up from the dealer, the service advisor who did my walk-around said that it wasn't necessary, and just to leave it on all the time. He said that unless the carb was old and the parts worn out, the float would do it's job and keep any fuel from flowing unless the bike was running. This does make sense as one of my other bikes has a petcock, but it's only accessible when the fuel tank is removed from the bike. Apparently it's not for everyday use, but for when you need to take the tank off for service.
So let's hear from the experts out there, who's right?
 
#4 ·
The way you wrote it, they both are. The manual is right if you want to insure that there is NEVER a leak as the bike sits unused. The "service advisor" [that's a new one for me] is right IF a carb float never sticks. Problem is, they sometimes do. I sometimes cheat if I'm just running into the store or going to get back to the bike in a short while. But if I am going to be gone more than a few minutes I turn it off.

The Triumph uses a gravity feed. Sue's Kaw and many of the Hondas I have owned have a fuel pump that has to pull a vacuum to bring the gas down to the carbs. On those bikes you never have to shut the petcock off because there is a little valve in the tank itself that shuts until the vacuum opens it.

Bottom line: what level of risk are you willing to take with gasoline? I always close the petcock on a gravity feed tank.

Monte :)
 
#5 ·
Technically, the service advisor. The problem is that if there's a problem with the carb (worn needle tip, tiny piece of grit etc) you won't know about it until it is far too late. A very small amount of gas is all that it takes to destroy the properties of your oil.

Think about going for a long ride after a pint of gas has seeped past the carb, into the cyclinder, past the rings and mixed with your oil. "Premature wear" only begins to cover it!

Turning the petcock to OFF is such a small effort...

Me? I'm so anal-retentive that I turn the gas off a couple of hundred yards shy of the garage, and run on what's in the float bowl until I'm parked. Engine rebuilds are expensive.

Alex
 
#7 ·
I know you should shut it off . I have been riding triumphs for over
30 years and I always shut it off when I shut down the bike or I would find a puddle of gas under the bike in less then 10 minutes.
That was on my old Bonnies. How ever, again I know I should BUT! I have
never shut off the gas on my new Bonnie since I've owned her new back in
2001 and she has never leaked a drop. I have read about a guy on here that had gas flowing out the air filter and seeping down the cylinders and
filling up the oil reservoir all of witch can't be good. I think it would be a good idea to make a habit of shutting it off.
I just never remember to.
Bill
 
#9 ·
How much does a complete bottom end rebuild cost?

A piece of dirt the size of a grain of sand in the float needle seat will flood the case with gas and the big end will be ruined in less time than it takes to say I left it on. When you re-start. Ask me how I know!, go ahead ask:(
 
#10 · (Edited)
A few years ago, I checked with Pingel to see if they had a vacuum petcock that would fit the Bonnie. I figured I could put a 'Tee" in a hose I would run between a vacuum takeoff point on each carb, and that would operate the petcock. That's how my W650 was set up.

At the time I didn't have the Part# for the manual Pingel unit. Pingel was cooperative, and asked me to provide several pieces of info about the Triumph unit. I did not feel like pulling the petcock out of the tank to get these measurements. So to date, I'm still running with the Triumph unit.

I'm thinking that the easy solution would be to ask Pingel if they have a vacuum petcock that is the same size as the manual one they offer for the Bonneville.

Can someone supply me with the PN for the manual petcock from Pingel? I'd be happy to run this past them.

Bob
 
#12 ·
Thanks, Uzidzit - I'll drop them a line.

Bob
 
#14 ·
I hate to disagree:D, but I think both are wrong. The service manager is wrong because the Triumph petcock doesn't shut off enough for safe tank removal...I have put a cup under the petcock when my tank was removed with fuel in the tank and the cup was nearly full in a few hours.

The manual is wrong for the same reason...if the carb is not functioning properly, fuel can get into the engine when the bike is parked for a long time because the petcock only slows the flow of fuel, it doesn't stop the flow as it should.

That is the reason to purchase a good petcock, IMHO--not the bogus reason that you need one that flows more fuel, because the stock petcock will flow many times more fuel than a highly modified twin can burn.
 
#15 ·
Redbird you have a defective petcock

In the off position a good petcock will not leak, mine do not leak a drop when I have the tank off, if your bike is under warranty go get a new one yours is broken. If not under warranty go buy one. leaking is NOT normal.
 
#21 ·
Personally, I only turn the fuel off when I put her to bed at night.
I think we should have a "blanket or duvet-for the Bike when we put her to bed"-thread. Personally, I would let her have a nice warm down-filled duvet.

:p
 
#23 ·
I've owned 3 bikes prior to my Triumph. I have always turned them off out of habit when not using them. I guess the habit stuck with me because i always turn it off as I'm getting off the bike. The real idea of this to me is that there is absolutely no danger in turning it off - there is sometimes problems with keeping them on. Mine doesn't leak one drop - tank on or tank off.

I like the idea that Oz was talking about where he turns the gas off the gas a couple of hundred yards from his garage, and run on what's left in the float bowl until parked. This kinda makes sense to me as well.
 
#24 ·
"The real idea of this to me is that there is absolutely no danger in turning it off -"

True. For me its remembering to turn it back on! I turn mine off, go into a cafe for a cup of coffee, get back on, haul out to the red light, stop, take off with a bunch of crazy cagers, get half way down the next block and it bogs down..........bummer. I spend a bit of time looking in my rear view mirror hoping not to get rear-ended while I switch that puppy over.

:HappyRoll: Monte
 
#25 ·
I'm another one of those "in the middle" guys. I switch mine off when it's going to be a long time. When i'm parked for the night, while i'm at work...anything where it'll be stopped for atleast a few hours. If I stop to run in some place I leave it on.

I suppose it's the smart idea to always shut it off, but I invariably forget to turn it back on when it was only a short stop. I've had a couple bikes with dodgy floats (flood the engine\oil with gas if you left it on and didn't ride for 30 - 40 hours) and even those were fine if you were only stopped a couple hours so I think it's fairly safe to do with a tap that isn't as worn out as those.

but, if you're not as scatter brained as me you might as well be safe and turn it off.
 
#26 ·
In the winter I ride the bike far less than in the warmer months. Not only do I turn off the fuel valve at the end of each ride, but If I know it will be awhile before I ride the bike again, I turn off the fuel valve and let the engine idle until it dies. My theory is that raw fuel in the cylider bores washes away the anti rust protection offered by engine oil on the cylinder walls, so if I let the engine idle until it dies from fuel starvation, this protection is retained to a certain extent. Also, there is now no fuel in the float bowls to gum up and cause problems.

If you fly light aircraft, the same effect is produced when you shut down the engine with the mixture gontrol rather than by using the ignition switch.
 
#28 · (Edited)
Just A Personal Technique. . .

I noticed a thread below about whether or not each of us bothers to turn off the fuel valve after each ride. It looks like there are lot of viewpoints on this question!

I always do. Also, if I know that it is going to be awhile before I'll be riding the bike again, I turn off the valve and let the engine die from fuel starvation. My theory is that this technique checks the positive functioning of the valve. It also burns the last of the fuel out of the float bowls, preventing evaporaton and gumming there, and keeps raw fuel from washing engine oil off of the cylinder walls, offering some short term anti-rust protection.

If you fly light aircraft, you know that this is part of the reason that the engine is generally shut down using the mixture control rather than the ignition switch.

What do you think, or am I just full of it (again)?
 
#31 ·
If you fly light aircraft, you know that this is part of the reason that the engine is generally shut down using the mixture control rather than the ignition switch.

What do you think, or am I just full of it (again)?

I don't think the idle cutoff burns off the fuel left in the carb though. Notice that if you pulled the mixture all the way out (idle cutoff) wait for the engine to die and then put it back rich and start it, it will. If the carb bowl was empty you would have needed to pump the primer a couple of times to re-fill the bowl before the engine would re-start. No? If you wanted to empty the carb, you'd leave it on rich and turn the fuel valve to OFF. (Which is not the normal 1)Idle cutoff, 2) ignition off, 3) fuel off procedure.)

On the bike, I've also shut off the petcock before arrival and ran the bowls dry but my bike doesn't seem to like the extremely lean condition that occurs before stalling. It makes disturbing noises from the valve area.
 
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