Topic: TURN OFF THE DAMN GAS!!!

[Sandcast 2356]

I accidentally left the petcock turned to open last night, all night, and woke to find a very wet engine block. it appears that the gas leaked out of the bowl drains. Is this normal?? and if not, what exactly is the reason for turning off the petcock when parked??

[Bob Wessner]

Ordinarily it is not normal, but if the floats stick, or float valve sticks open the fuel keeps running into the bowls and then overflows. I may not happen while riding because you consume fuel and/or the vibration keeps things functioning. All that said, it is always a good practice to shut-off the petcock when you shut the engine off.

[Harry]

Yep, you guessed it, turn off the gas on these bikes. In fact, I turn off the gas a coupla hundred yards from home, I like to believe I will fill the carbs with fresh gas when starting next time! Whatever, I never had a carb empty itself on my floor. Newer bikes have vacuum-dependant petcocks and switching off the tap is really an ancient ritual, something most of the kids today never heard of, but something which bonds us in commo brother/(sister)hood. So, the gas puddle is really an initiation rite, and.....what? Oh! Alright, I´m coming to bed, dear (he, he, sorry, gotta go........)

[SteveD CB500F]

This is very common and you will read a lot of posts on this subject (carb cleaning)

The floats in the carbs turn off the fuel flow so in a perfect world, you shouldn't need a fuel tap (petcock to you guys).
In the real world however, any dirt will stop the float valve from closing completely leading to an overflow from the carbs. It may also allow fuel to drain into the engine which will dilute your engine oil if left for a long time.

Sometimes tapping the recalcitrant carb will dislodge the dirt and stop the leak.
Otherwise you'll have to remove the carb bowls and clean the float valves.

[supersport_CB400F]

Turning the tap into the OFF position is all about gravity, the tank has a head of petrol and it wants to go into the carbs if it’s not getting into the engine while the engine is running then it has to go some place. If the floats  are not quite right then it should go down some overflow pipes onto the road, if you have no pipes then it hits your engine, If the engine is hot you may get a fire it’s simple  fix the carbs  and turn the petrol OFF if the bike is parked, it’s  a safety feature of these bikes. If you don’t then the bike will burn one day, it’s common sense hot engines and petrol don't mix on the outside.

[scout18]

When I was young I drove a Kawasaki mach III that had a sticky float. One time I didi not turn off the gas and got on kicked her over and whoooof. bike on fire. Luckily a passing motorist stopped and threw me a fire extiguisher and I got it put out. But not before frying all of the oil injector lines. You have not lived until you have a flaming bike between your legs. Learn from my mistake. If you can see or smell gas find out where itis coming from. It burns hot. By some miracle I was not hurt .

[heffay]

whoooo hooooo! flaming crotch... not my cup-a tea.  moral of the story.  off is good.

[cb750_chris]

I just found a crank case CHOCK full O gas in my GS850.  I rebuilt the petcock already so here goes again.  I think this time I'll put a valve in the line for storage since it is vacume operated and doesn't have an off position.  Welcome to the world of vintage bikes Nathan.  You'll have that thing fixed up one part at a time before you know it.

 P.S. Do these things have the problem of gas in the case like my Suzi?  If so someone should recomend and oil change to Nathan. 

[Sandcast 2356]

Thanks for the responses guys, I don't know what I'd do without this forum. P.S. how do you remember to turn to gas back on??    That was an interesting time trying to figure out why my bike suddenly putted to a stop in traffic and wouldn't start again...

[eldar]

I have never had this happen to me. What are you people doing!!?

[Gordon]

Sure!  And I bet you've never forgotten to put the kickstand up before riding off either. 

[Terry in Australia]

I just found a crank case CHOCK full O gas in my GS850.  I rebuilt the petcock already so here goes again.  I think this time I'll put a valve in the line for storage since it is vacume operated and doesn't have an off position.  Welcome to the world of vintage bikes Nathan.  You'll have that thing fixed up one part at a time before you know it.

 P.S. Do these things have the problem of gas in the case like my Suzi?  If so someone should recomend and oil change to Nathan. 

G'Day Chris, ah, it's so good to have another GS Suzy rider on board, aren't they great bikes? I've got a GS750 and GS1000S, plus another couple of GS1000's in bits, they're my other infatuation.
You just rebuilt your petcock? I'm betting that you put the spring on the wrong side of the diaphram, effectively holding it open. As you know, the CV carbs don't have drain hoses (why would you need them, vacuum taps don't leak?) so when the fuel fills the float bowls, it then continues into the cylinders with open inlet valves, or into your airbox, or both. Pull your petcock apart again, and place the spring on the other side of the diaphram, and your troubles will be over! Cheers, Terry.  

[SteveD CB500F]

P.S. how do you remember to turn to gas back on

Experience / Habit (delete as applicable)
Kill Switch
Sidestand
Fuel Tap
Ignition

It's like getting out of bed in the morning!

[eldar]

seriously, I have never had my carbs leak after setting a while with fuel in them. Even after my bike had to sit for a month. I have a 78k and maybe the float bowl and needle work better.

[SteveD CB500F]

My '72 500 does it all the time, even if left for 10 minutes with the tap on.

[CHUNG]

That's why almost all bikes past the late 1970s had auto shut off on um. They will sometimes leak pretty bad even with new needles and seats. Better check your oil too, it's probably full of gas. Not a good thing.

[cb750_chris]

After rebuilding my vacume type petcock it was fine for a couple of seasons.  I did some tinkering a few months ago and for some dumb reason put my brake vacume on it to see if it could make it operate that way.  I didn't put too much vacume on it.... Just enough to open the valve.  Seeing as now it's messed up I'll never do that again. 

Good thing about regular petcocks.  They actually have an off position.  You'll learn to appretiate it when you ride a bike without it. 

[heffay]

P.S. how do you remember to turn to gas back on??

dont have a pic of this aspect of my ride but, the piece of fence board that my side stand rests on has "turn on gas" sharpied onto it.  my driveway has about a 10-12% incline on dirt and has a reverse bank... sucks to run outa gas on that!

[gratznic]

Please excuse my dumbness, but how exactly do you check oil for gas contamination? Is it an issue of settling?

I had some overflow due to a stopped jet, and I'd like to figure out if I should replace my oil.

Thanks.

[rob]

I am glad someone brough this thread up, I always leave the petcock on the 'on' position for days.  Luckily i've never experienced a fuel leak.

Are there any other things like this one should know about?  Someone mentioned having the kill switch off?  I usually just leave it on, is there a risk of draining the battery, etc?

Rob

[El Taco]

It's all about odor. If your oil smells like gas, then change it.

A puddle under my CB550/500 is nothing new to me. Can't seem to get the valve to actually shut off.

[El Taco]

Oh, and leaving the kill switch on does nothing without the key.

[Uncle Ernie]

When I forget to turn off the gas, I do 2 things; 1) smell the oil to see if gas is in there ( If I have the slightest suspicion, I change the oil). 2) Take out the plugs and turn it over a couple of times. If gas gets into your combustion chamber, the bike will not start and you might blow a gasket. Liquids don't compress !!!! If you slame a piston up, the gas that has leaked in there has to go someplace. If you take out the plugs first, it will come out that hole.

[Bob Wessner]

Wouldn't any raw gas in liquid state getting into the cylinders just leak down into the sump via the ring gaps and grooves?

[Terry in Australia]

Wouldn't any raw gas in liquid state getting into the cylinders just leak down into the sump via the ring gaps and grooves?

Yeah Bob, it will, but you can't guarantee that it'll flow past your pistons into your sump as quickly as it fills the cylinders. Either way, you don't want it to happen. If it fills your sump it'll wash the oil out of your bearings and destroy your engine if you actually ride it in that condition, so either way, "TURN OFF YOUR DAMN GAS!", HA HA! Cheers, Terry.