Reserve does not work

[DGXSER]

Old Skool, you mistook my post. My intent was to say that your condemnation of Davinci's idea might have been a little premature. The "I'm Stupid" look was just to say that is the look I wore when I discovered the petcocks being off. Of course it went away after I realized no one else was watching. I had no intention of suggesting you, or anyone else but me, looked stupid.

Yes I know that ClCorbin has owned the bike a long time and probably does know how the petcocks work. He probably already checked all the little things I have mentioned to. Then again, I for one have been turning petcocks on and off for alot of years. And yet, it took pushing that fat heavy pig 1/2 a mile up hills to figure out I had not yet turned them on.

So, it never hurts to check the obvious, especially when alot of the less than obvious sources have been eliminated.

[old_skool]

Sorry, you guys don't get it, I wasn't trying to condemn Davinci for for his idea, it was half in jest and half "we don't need to ask if the key was in the ignition instead of his pocket" overthinking it...c'mon guys, not everything contradicted is an attack, and I hope Davinci didn't think it was. I guess I should have put one of these.... at the end and all would have been well.

[Rasputin]

At the risk of sounding stupider than usual I must say something. I bought my 79SF new off the showroom floor, and until I joined this forum did not know which way was on, off or prime. My octy, floats, everything else did the job they were intended to do. I never had fuel in my oil and it never failed to work as new. The only reason I even got to looking was because I wanted to install pods. I will never put a set of pods on a bike again because of the hassles. I do however say that once I found the site that I am more informed and am now addicted to fixing these old girls up.

[DAVINCI]

Sorry, you guys don't get it, I wasn't trying to condemn Davinci for for his idea, it was half in jest and half "we don't need to ask if the key was in the ignition instead of his pocket" overthinking it...c'mon guys, not everything contradicted is an attack, and I hope Davinci didn't think it was. I guess I should have put one of these.... at the end and all would have been well.

No, I really could not care less about your opinion of my knowledge or advice, I'm not here to please anyone but myself, so don't give my feelings a second thought. After all, this is only the internet.

[TopCatGr58]

Another Opinion/idea?

It's been awhile since I had my tank off and petcocks off and apart. IIRC, the petcock screens can be removed and turned around 180 degrees?

Wondering if it's possible that when he took it apart, that he might have put the screen in 180 degrees out. The fiche shows the blocked off part of the screen on the front edge of the petcock. Also...lots of dirt/gum can get into the screen blocking the flow...especially close to the bottom where all of the junk in the tank forms, and lots of folks never get down to or use the reserve, so the fuel gets stale/concentrated, and more easily forms the gums around the screen at that point!?

He said he still had fuel left in the tank after running ON dry. I would wonder if he had tried draining the fuel using the reserve setting first...and then after it stops flowing, switching to ON to see if he could get any more flow?

Good Luck Corbin.

T.C.

[natemoen]

Another Opinion/idea?

It's been awhile since I had my tank off and petcocks off and apart. IIRC, the petcock screens can be removed and turned around 180 degrees?

Wondering if it's possible that when he took it apart, that he might have put the screen in 180 degrees out. The fiche shows the blocked off part of the screen on the front edge of the petcock. Also...lots of dirt/gum can get into the screen blocking the flow...especially close to the bottom where all of the junk in the tank forms, and lots of folks never get down to or use the reserve, so the fuel gets stale/concentrated, and more easily forms the gums around the screen at that point!?

He said he still had fuel left in the tank after running ON dry. I would wonder if he had tried draining the fuel using the reserve setting first...and then after it stops flowing, switching to ON to see if he could get any more flow?

Good Luck Corbin.

T.C.

Cant do that on the standard petcocks. There is a tap that comes off one side with the locating pin/rivet.

[clcorbin]

He said he still had fuel left in the tank after running ON dry. I would wonder if he had tried draining the fuel using the reserve setting first...and then after it stops flowing, switching to ON to see if he could get any more flow?

So, to answer a few questions that have popped up over the last day or so:

1) Yes, I DO know what the positions are on the petcock. Handle down is "On", handle forward is "Res" and handle backward is "Prime". There is no "Off" position unless you mod both the plate to remove the tab AND the handle to shorten it so it will clear the gas tank when you turn it straight up. Which I have not done.

2) After 24 years, I am STILL learning new things about my bike. Of course, the new knowledge tends to be a bit more esoteric than where the key is, how to remove the oil filter, etc. Probably the most recent "aha!" moment was when I learned (from here) that not only is there something behind those little chrome caps on the bottom of the frame, but adjusting that something can have a BIG difference in how the bike handles. That would be the swingarm bearing preload.

3) No, I have not started draining the tanks from the Res position and THEN switched to the On position to see if I get any more gas after it stopped in Res. That might be an interesting experiment.

4) I THINK the petcocks are assembled correctly. On the standard petcocks, there are not a whole lot of ways to put them together incorrectly UNLESS you mix parts from the left and right assembly, which I THINK I have kept straight as I can't remember taking them apart at the same time. The key there is "remember" along with "24 years of ownership".

So, I think my next plan of attack needs to be to remove and disassemble the petcocks and then soak the whole mess in something like Seafoam overnight to see if there is any gum up in the main housing/filter tower area that I simply can't. That will be followed by a very close inspection when I reassemble them to make SURE that I haven't swapped anything around over the years. If that doesn't get reserve working, I'll probably see about modifying this thing to get rid of reserve all together but allow me to get more of my gas out of the tank. I'm tired of giving up on 25% of my fuel...

I would like to ask that we bring the focus back to the issue. I'm not offended if someone asks a question that might seem basic. Hell, if I had a nickle for every time I DID do something silly/stupid like that, I would have a hell of a lot of nickles! I do appreciate everyone that has taken time to read, and even more so, reply to this thread trying to help me.

[fredintoon]

Hi Clint,
"What you describe cannot be caused by that which you have stated."
(That's a newspaper columnist's reply to "worried Browneyes of Brighton" but it seems appropriate to this discussion.)
You had this bike since 1989, did it always not have a reserve or has that just occurred or have you simply not noticed it before?
Didja doublecheck that when no more gas would come out that there was a reserves-worth of gas still in the tank?

[cywelchjr]

If you have inline filters you MIGHT consider removing the screen from the in tank filters to remove that as a possible problem as if the screen below the pipe that creates the reserve area might be clogged, if you remove the screen material from them, that would remove that possible problem, but that would also get rid of that filtration, making them like aftermarket petcocks.

[XS1100_OEM4ME]

Tank filters

The tank filters are there to filter the gas and add a res. function to the tank, they almost never clogg on a bike in use. You have a gasket problem in the pectcocks in MHO, If you have gas left in the tank no matter where you turn the petcock there is someting not letting the fuel flow because there is no opening from tank to carb, find the block, fix the problem

[Rasputin]

Just to avoid confusion about the petcocks I took one of mine apart. This is the left one I am quite sure but I could be wrong as I have not had this bike since new.
The point I am trying to make is that one can not reverse the rubber gasket, nor the filter tower itself. The backside where the diapraghm is does nothing as to fuel flow except to allow it.
I myself have reversed (left to right swap) a few of my bikes because I prefer the handle pointing opposite to the indicated positions. One of my throwbacks to earlier years when they had a pointer opposite the handle to indicate the position.
Not much can go wrong with the fuel flow unless one of the components is in the wrong position.
If yours do not look like these for any reason you may find the problem there. Good luck!

[DGXSER]

Thank you VERY MUCH for those pics Ras, cleared up alot for me. Combine that with the answers to previous questions so far, and here is my thoughts.

My thought is that perhaps you have low vacuum in the line to the petcock which might be slightly plugged. So it is not providing quite enough vacuum to open the diaphram on its own, and it needs the pressure of more fuel in the tank pushing on it to "help" it open. When the fuel gets down so low, the pressure it excerts will also drop. Which could be less than the "help" needed to open the diaphram.

Otherwise, yes, your filter has something clogging it in that lower region. That is the only two things left that make sense to me.

[ViperRon]

Clean out

When I cleaned my petcocks there was like a corrosin skin inside the valve. What I used to clean it was a piece of braided wire that you use to hang pictures. I folded it over and stuck it in a drill running the folded end into the openings. It works quick and efficent and causes no damage.

[clcorbin]

Thanks for the photos! The last two pictures REALLY help!

So let's see if I have the ports figured out on this thing:

1) The TOP port is where the fuel comes in from the top part of the filter screen.

2) The middle port to the left is just a plug and does nothing.

3) The middle port to the right is where the fuel comes in from the reserve (aka: lower) part of the filter screen. Note this also implies that normal and reserve have two entirely separate ports bringing fuel to the distribution valve in the petcock.

4) The center port is the gas outlet to the carbs and is currently blocked by the vacuum diaphragm that you can just make out in the photo.

5) The lower port is where fuel bypasses the diaphragm for prime mode.

Now we look at the vertical slow and the curved slot in the handle:

1) In the "On" position, the curved slot is connecting the prime port and the plug. Aka: doing nothing. The straight slot is connecting the top port and the center port so fuel will flow from the upper part of the tower out to the carbs, but only when the diaphragm is pulled back by engine vacuum.

2) In the "Prime" position, the straight slot is connecting the plugged port to the center diaphragm controlled outlet. Aka: Nothing if the engine is NOT running. But the curved slot is positioned so it is connecting the reserve port to the bypass port, letting fuel flow from the reserve section of the tower even with the engine off.

3) In the "Reserve" position, the straight slot is connecting the reserve port to the center diaphragm controlled outlet. Fuel will flow from the reserve part of the tower out the center port, but only when the engine is running. And, the straight port is connecting the normal port to the plugged port. Aka: nothing.

So this REALLY has me scratching my head. I KNOW the normal port works. Bike runs down for about 4.2 gallons. Reserve does NOT work. But here is the kicker: Prime DOES work because I have used it on a couple of occasions when I managed to squeak into a gas station on two cylinders! Two carbs are completely empty, but I put both petcocks on prime before filling the gas tank and the bike fires up on all fours when I am done like nothing has happened, even though I KNOW two carb bowls where pretty much completely dry prior to filling the gas tank. And it appears that prime and reserve both use the same port from the tower, so that is weird.

Other than the screens, did Yamaha make the reserve port so it could draw from the upper and lower sections of the tower? Which would explain my issues IF the lower part of the reserve port was plugged, but the upper part was still open. The problem is, I can't figure out how to get the filters off the towers to see what is going on in there without damaging them. Any ideas on this?

And I do run inline filters that I change out about once per year (around every 10k miles or so at my current riding rate), so loosing the tower filters isn't that big of a deal I guess. But I sure would like to figure out what in the hell is going on in there! And prey that it isn't all inside my head instead!

[Schming]

This is the...

...orientation of the petcock handles and their corresponding plates. Just maybe something is mixed up. HTH