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Hi! I just purchased a 1986 VT700 and I found that the fuel cutoff valve was jammed in the "on" position. I text the person I bought it from and she had no clue the bike even had one so she said I shouldn't have a problem cause she never moved it out of the "on" position.

After taking the MSF Course (Just got my license) the instructor said gasoline would pool up into the engine if that wasn't off while parked. But considering the previous owner never had any problems, should I be worried about this?

-Thanks!
 

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There is not a manual shut off valve on your bike. I think it has a fuel pump with a vacuum air fuel cut off. When it stops running the fuel pumps stops and it automatically shuts the fuel flow off. MSF instructors give general information not bike specific information. I suggest you try and find a Service Manual for your bike.

And welcome to the forum.
 

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If you want it to work just find a replacement on ebay.
 

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There is in fact a manual fuel cut off valve on the 86VT700c. No need to worry because the fuel pump, when not running, will not allow fuel to flow to carbs. My shut off hasn't worked in years.
 

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Part# 16950-MK7-005 Petcock Assy. Not available. If anybody knows where there is NOS available let me know. Some parts houses online show available until you place order then say out of stock after placing order. Been chasing this part for a few years now. No luck on cross reference either.
 

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No need to worry because the fuel pump, when not running, will not allow fuel to flow to carbs. My shut off hasn't worked in years.
There is no doubt, that fuel WILL pass right through the fuel pump, running or not. Search the forum and you will find many examples...

While it is possible that leaving the petcock on can result in an engine full of gas, it is also not that common. It is up to each of us to decide whether to shut the fuel off every time we shut off the bike. The more carbs a given engine has, the greater the risk of a hung inlet valve creating a problem.

I shut my fuel valves off at the end of the riding day...
 

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Gat803, from owners manual page 23. "The manual fuel valve set it to on position for normal operation. The off setting is only for long term storage or servicing of fuel system components. Automatic fuel on-off. With the fuel valve set to on, fuel flows to carburetors only when engine is being started or is running. A diaphragm in the fuel pump shuts off fuel flow when the engine is turned off" The only way fuel can pass thru fuel pump to carbs when not running is if pump is bad.
 

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Gat803, from owners manual page 23. "The manual fuel valve set it to on position for normal operation. The off setting is only for long term storage or servicing of fuel system components. Automatic fuel on-off. With the fuel valve set to on, fuel flows to carburetors only when engine is being started or is running. A diaphragm in the fuel pump shuts off fuel flow when the engine is turned off" The only way fuel can pass thru fuel pump to carbs when not running is if pump is bad.
Right. And wrong.

The vacuum actuated fuel valve at the petcock often doesn't work as well as it should, thereby passing fuel even when the engine is not pulling a vacuum, ie; not running.

Most motorcycle fuel pumps are indeed, diaphragm type pumps. But, this has nothing to do with whether or not they will pass fuel when they aren't running. This style of pump still has two small one way check valves internally that do allow gas to pass thru, again running or not. This situation can occur at any time. The pump does not have to be defective for it to occur.

Now, it does take a certain amount of misfortune to happen all at the same time. First, the vacuum petcock has to have a weak enough diaphragm or spring to pass fuel. This condition is not unheard of.
Next, the inlet valve/float in the carb has to become fouled/defective, allowing fuel to flow to excess even when the engine is not running. Again, this is not unheard of.

Once this set of circumstances happens and fuel starts flowing into the engine, it can continue to siphon gas until the tank runs dry or the inlet valve/petcock gets closed.

You can believe this or not, as you will. But the fact is....it does happen. Again, do a search on the forum, there are many examples. Over the years, I have had this happen at least half a dozen times on various pieces of equipment. Many people never have it happen. Vacuum petcocks do reduce the chance of it happening, but don't eliminate it.

Some time ago, someone else tried to posit the same thing as you, I documented a test where I used an old fuel pump, some clear hose and some gas to demonstrate that gas will in fact pass straight thru a good fuel pump. Like I said, do a search....

Lots of things don't work quite as well as the manufacturer claims. This is one of them.
 

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Which leaves us where if the shut off valve is not available? Buy used, done that and got burned. Install aftermarket universal, hard to do since valve handle comes thru left side cover. Try to install somewhere inline, very tight and would need to remove side cover each time to close valve (PITA) Been chasing this for sometime now, so far no signs of gas passing thru (lucky?) On the 86 with the sub tank stuffed in there room and access is the problem.
 

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gat803 I'm not disagreeing with you. The very thing you said happened years ago on my CM400T. Not sure if that had a pump or not. Float stuck open and gas leaked out the overflow tube. Lucky it didn't fill crankcase. I now check oil always before starting, lesson learned. Keeping these old bikes on the road can sometimes be a challenge. I'll figure something out eventually.
 
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