Fuel petcock

[MattK]

I'm sort of embarrassed to admit this, but I just realized that this bike ('83 VR) has a fuel petcock. Do I need to be shutting off the fuel every time? Looks like it hasn't been moved in a while. I found it, but the twist part on the front is smashed a bit, and I can't turn it. I found replacements online for like $20, but they just have a little nub on the front, is there a larger knob that is not shown? Should I bother replacing it?

 

[BlueSky]

http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1983/XVZ12TK/FUEL+TANK/parts.html

 

They are still available from Yamaha if you want a factory unit. If you leave the bike sitting for a long time you should turn the fuel off and drain the carbs. I think these bikes have overflow tubes that will prevent hydrolocking if the fuel needle fails to hold. I know my 2004 Kawasaki Concours did not have carb overflows and the fuel valve was vacuum operated. So, if the vacuum operated fuel valve failed and the carb fuel needle failed the engine would fill with fuel and hydrolock. It did happen too.

 

Yes there is just a stub to turn and mine is tight enough I have to use pliers on it to turn. But, it works fine.

Edited April 10, 2017 by BlueSky

[cimmer]

On these bikes, with the petcock lower then the carbs you dont have the possibility of overflowing the carbs by leaving it on plus we have an electric fuel pump that pushes the fuel to the carbs. I personally have left mine in the reserve position for the last 10 years or so and have never had an issue with doing that.

Bottom line is you should be just fine with leaving it as is.

Rick F.

[bongobobny]

Yup! My feelings exactly, just leave the petcock on the reserve position! The 1st gen petcocks were stiff to begin with and you pretty much needed az pair of pliers to turn them! There was a "mod" using washers behind the screws to remedy this...

[zagger]

After years of not messing with it, a year ago I suddenly had a bright thought that I should be turning off the gas before storing it for the winter. Trying to turn the little plastic shaft, I promptly snapped it completely off and was forced to drain the tank and install a new valve. I've gone back to my original operating procedure of just forgetting about it!

zag

[BlueSky]

On these bikes, with the petcock lower then the carbs you dont have the possibility of overflowing the carbs by leaving it on plus we have an electric fuel pump that pushes the fuel to the carbs.

Rick F.

 

The elevation of the petcock doesn't matter. It's the elevation of the fuel level in the gas tank relative to the elevation of the fuel level in the carbs that determines if it will gravity drain. But, the fuel pump may not allow fuel to drain through it with the bike sitting.

[snyper316]

Yup! My feelings exactly, just leave the petcock on the reserve position! The 1st gen petcocks were stiff to begin with and you pretty much needed az pair of pliers to turn them! There was a "mod" using washers behind the screws to remedy this...

 

 

MKI don't have a reserve on them at all there on or off. The MKII have 2 screen straws as the MKI have just the one. Even a brand new one is stiff, it may not break right away but unless you really need to shut the fuel off I would just put it on turn it on and forget it.

[bongobobny]

Only the MK1 Standard, and perhaps only the '83, did not have the reserve. The Royales had the reserve...

[Flyinfool]

I am another one that never touches the petcock.

 

With a full tank of fuel the fuel level will be above the float level in the carbs, So if the pump and float valves fail it could allow gas to drain thru the carbs. the overflows should let the gas drain out on the floor before overflowing into the engine. I would really hate to turn that thing, crack it without noticing the crack (because they are soooo easy to turn) and then have it fall apart on the road and leave me stranded with no gas and a tank that will not hold gas.

[Yammer Dan]

With a stuck float you could drain a full tank out on a new garage floor but I don't touch it!!!

[snyper316]

Only the MK1 Standard, and perhaps only the '83, did not have the reserve. The Royales had the reserve...

 

This I did not realize, Wonder why the Royales got the reserve. I may even have an aftermarket one, if there is such a thing. The one he shows in that picture has got me wondering because I don't know for sure if mine was that short. All I know is mine is slightly on the stiff side. I am thinking 83-84 may have been the years I have thrown that box away long ago. I am also thinking there was other Models listed to but will not swear to it.

[bongobobny]

Pretty much all of the petcocks on the 1st Gens were stiff, due to kind of a design feature of the actual mechanical switch. They are known to bind! Someone, a long time ago, came up with a simple mod that helped this out by simply adding flat washers to the screws which brought the mechanical mechanism out a little further to help alleviate the mechanical binding...

[BlueSky]

So, you guys are saying that you leave the petcock on and don't drain the carbs when leaving it sit for a long time or you drain the carbs and the fuel pump prevents the gas from refilling the carbs?

[videoarizona]

 

 

[/color]I see conflicting information in the posts above. Unless, of course, my lack of coffee this morning is causing a brain fade. Here's my conflicting thinking:

 

It is my understanding that due to the low location of the tank on the 1st gens, leaving the petcock on will not cause any issues unless the fuel line going to the pump goes bad. That's below the level of the tank at all times. The pump is too, but it "shouldn't" allow fuel to flow without it running. You can run a first gen without the pump, but the fuel level must be high enough for gravity to provide the pressure to work. And you must run a fuel line from the tank to the carbs. cowpuc had a nice post on this forum somewhere.

 

Other than that, the carbs are higher than the fuel level in the tank unless the tank is topped. So very little, if any, fuel can get to the carbs if the carbs leak. (unless the leak occurs while you are running). Gravity is your friend here. The 2nd gens have the tank on top...so shutting off the fuel is a mandatory thing, unless you are willing to take a chance of having something go wrong in the fuel system, leaving gravity no longer your friend and fuel all over the place.

 

So to answer your question, yes and no. Most of us put the 1st gen petcock on reserve position and leave it. The danger of breaking the thing while on the road is greater than the danger of having a carb go nuts on us. If we keep our engines running properly, we should never get a stuck float. (hah) Of course, dirty gas on the road at a station in the middle of nowhere can do the trick...but for the most part, the 1st gens have been pretty good at not having leak issues...or...hydrolock issues due to fuel flowing.

 

Now for winter storage...that's a whole other ball game. Every thing I've read says full fuel, treat it and go away. My dad used to do the opposite. Drain everything and leave it. He never had issues after a New England winter. His snowblower started each season, his lawnmower started each season.....so I think if I was in the northern latitudes, I would do the same. Why tempt fate?

 

So there ya go. Either this post will get more answers back to you or not. But it's what I believe.

Your choice really.

Edited April 13, 2017 by videoarizona
clarification

[BlueSky]

What I believe is that the carbs should be drained when leaving it sit for a long time. I've never tried stabil in the gas so perhaps that would prevent the carbs from getting plugged from the dried up gasoline. I drain my gasoline powered pressure washer carb after learning the hard way or rather I turn off the fuel and let the carbs run dry. My riding lawn mower will run after sitting without draining the carbs. But, I run it periodically even in the winter to rake the yard. Running around the outside of the yard blowing the trash into the center saves a lot of raking. Motorcycle carbs seem to be paritcularly sensitive to plugging up after sitting. My next motorcycle WILL be a fuel injected.

 

I keep looking at those Honda ST1300s on craigslist!!

[bongobobny]

Going from memory here, but I think the top of the gas tank is still below the level of the fuel bowls anyway, so even if something were to happen to the fuel pump that it became a wide open hose, the level of gas still would not reach the bowls, especially if the tank is less than full to the top! Yes, it is ideal to drain the bowls if the bike is going to be stored for a very long period, like in excess of 6 months. Otherwise, using a good fuel stabilizer such as Stabil is a great practice...

[snyper316]

Redneck Fuel petcock, mason jar, thumb, hose clamp, and a bolt. Loosen fuel line from pump place thumb over hose so don't leak everywhere then place funnel in mason jar and get bolt and screw it in the end of the hose then tighten the hose clamp. There you have it fuel is now shut off... empty bowls in mason jar, then empty mason jar in gas tank.