Petcock again?

[Chiefy]

Caramba.  Where to start?

When I got my bike with 45,000 miles, I would hit reserve at about 85 miles.  But I was getting around 30mpg, so it only took about 2 1/2 to 3  gallons to fill up.  Switching to reserve for a few miles then back to "on" didn't change anything, I still had to switch back to reserve after a couple of miles.

Based on what I've read here, I decided the petcock diaphragm was getting weak.  Instead of rebuilding it, I just put a new OEM on it.

I was then routinely getting around 125 miles or so to reserve.  Every once in a very great while I'd have to switch at 85 miles (again) but it was not often enough that I was concerned.  Now, the last 3 tankfuls in a row I'm hitting reserve at 85 again.  Only need up to 3 gallons to refill.

Facts..... The petcock is less then a year old.  Probably less then 3000 miles on it.  Speed doesn't seem to matter.  It happens whether I'm riding mellow or fast.  There is an external fuel filter in line.  Probably around 6000 miles on it.  The tank has no rust in it.   Except for this, the bike is running perfectly fine, and nothing has changed.  Vac line from carb 6 to petcock is about 14 months old.

If I have to fix the petcock again, I will, and I'll use a Pingle this time.  But I hate to throw parts at a problem if I'm not sure what's going on.

So, where would you guys go from here?

[ryord]

I have had the same problem, usually when I am about 3 gallons down, warmer weather and highway speeds. When I switch to reserve it recovers. Petcock about 1 year old. I took off the inline filter and thought the problem was solved, but no.It was better however. I spoke to Rich  redeye tech. He seems to think the carbs are being cooked by heat from the engine. I am still chasing that gremlin.

[Chiefy]

I have had the same problem, usually when I am about 3 gallons down, warmer weather and highway speeds. When I switch to reserve it recovers. Petcock about 1 year old. I took off the inline filter and thought the problem was solved, but no.It was better however. I spoke to Rich  redeye tech. He seems to think the carbs are being cooked by heat from the engine. I am still chasing that gremlin.

I'm missing something.  If it's engine heat, I can't imagine it would always happen at the same mileage.

We seem to have bought ours around the same time.  Wonder if it was a bad batch?

[BonS]

Restrictive filter and/or fuel line kink. My fuel line was just a bit too long and would kink when the engine got hot. I cut off a smidgen and all was good.

[Chiefy]

Restrictive filter and/or fuel line kink. My fuel line was just a bit too long and would kink when the engine got hot. I cut off a smidgen and all was good.

Thanks, I looked for that first go around, but I'll check again.  However, this doesn't appear to be heat related, always around 85 miles.  Engine rpm or MPH doesn't natter.

[GOOSE]

get the pingle.

[valky1500]

The vacuum petcock can cause several problems and we will focus on this one here. In the RUN position the fuel is fed by engine vacuum and it only flows freely.

Another vacuum line also opens the plunger inside the petcock and it drops to shut off the fuel line to the carbs when the level in the tank reaches about 1.3 gallons. This is the reserve and can be used  once selecting that position on the petcock.

Simply putting gas into the tank and then driving off is where the problem begins and will leave you running short of miles until reserve is reached again and too soon. It leaves you running down the check list too long to mention of what's happening here. Of course you didn't forget to turn the petcock from RESERVE back to RUN, but what you did forget was to RESET the plunger inside the vacuum petcock. What does that mean?

It means that before you put gas back into the tank you first need to switch the petcock from the RESERVE to STOP positions and then fill it up all to your hearts desire. Doing that allows the plunger to reset once you select back to the RUN position and then start up to drive away. It allows the RUN/RESERVE cycle to happen all over again.

Yes,  the vacuum petcocks are designed to happen that way.

[Blackduck]

Sorry there is only 1 vacuum hose on the petcock and NO reset plunger.
Main or reserve is controlled by the position of the selector.
There is 1 and 1 only plunger attached to the vacumm diaphragm and this is controlled soley by vacumm and the return spring when the vacuum drops.

[Bone]

The petcock on my 98 Tourer works differently. It has a stand-tube that determines when you go to reserve. The gas level goes below the height of the tube you run out of gas. You then manually switch the petcock lever to the reserve port which is fed by a lower opening in the petcock which gives you approximately 1.1 gallons of gas. When that is gone the tank is empty.

[Blackduck]

Bone, yours is not different, that is the way they all work. The vacuum diaphragm only controls the flow of fuel when the engine is running or shutoff. It has nothing to do with main or reserve, as you say that is selected manually
Cheers Steve

[dubsider]

now that is settled (hopefully).. what is causing Chiefy's 85 to reserve problem? 

[Blackduck]

Dubsider, like your thinking.
With the same volume of fuel being required at 85 miles it sounds like a restriction ( kinked hose?)
When the hydrostatic head drops there is not enough flow to the carbs.
Cannot see where it would be drawing air into the system at the same point each time.
As the reserve works there is no sediment clogging the screen ( Chiefy also said the tank was clean)
Indeed a strange one, as it is intermittent it is going to be a fun one figuring out just what is causing it .
A possible check would be to manualise the petcock (move the spring onto the fuel sidew to hold the petcock open) and if it still needs reserve at 85 miles. Just need to make sure the manual part of the valve is shutting off the fuel flow. If the petcock is not aligned correctly to the selector knob it can hold the valve off it's seat allowing fuel to flow in the off position. Leave the fuel hose and see if fuel flows when the selector screw is tightened, if it does you need to loosen off the petcock holding nut and turn the petcock till there is no side load on the petcock stem.
Cheers Steve

[Chattanooga Mark]

Could the vent line be clogged or kinked causing a vacuum in the tank and not allowing gas to flow as normal. If you open the gas cap at the magic 85 mile mark, do you hear a swoose sound like air is entering the tank. I've seen that happen on many a Moto Guzzi until the one way valve on the vent line was removed. I don't think there is a one way valve on the Valkyries ventline but if it's not flowing enough air, a vacuum could be created in the tank thereby stopping the gravity fed fuel from flowing.

Just a thought,

Mark

[ryord]

It seems to me and I have heard this before, when the tank gets down about 3 gallons it has to do with pressure from lack of fuel being restricted somehow and not being able to push through to the carbs. This is why it always seems to happen when the tank is about 3 gallons down or around 80 85 miles.

[Chiefy]

Could the vent line be clogged or kinked causing a vacuum in the tank and not allowing gas to flow as normal. If you open the gas cap at the magic 85 mile mark, do you hear a swoose sound like air is entering the tank. I've seen that happen on many a Moto Guzzi until the one way valve on the vent line was removed. I don't think there is a one way valve on the Valkyries ventline but if it's not flowing enough air, a vacuum could be created in the tank thereby stopping the gravity fed fuel from flowing.

Just a thought,

Mark

I've checked the vent, it looks okay.  Still, would switching to reserve defeat the issue you describe?

[Willow]

A few questions:

Did you replace the vacuum line to the carb when you replaced the petcock?

Do you have a quick release connection on the fuel line?

Can you get it to recover by opening the gas cap when it starves at 85 miles? (That was was already asked.)

Do you have an inline filter?

[Gryphon Rider]

What I have to say is a summary of and in agreement with everyone above except Valky1500, who must be talking about the valve on a different motorcycle.  Possible causes for your symptom, all of which will get worse as you burn fuel and thus reduce the fuel pressure (hydraulic head):
1. Fuel restriction due to
     1.1. Clogged or undersized aftermarket fuel filter.
     1.2. Clogged screen inside the fuel tank.
     1.3. Kinked fuel line.
     1.4. Vacuum function on fuel valve not opening all the way due to
            1.4.1. Tear in vacuum diaphragm.
            1.4.2. Leak in vacuum hose.
2. Lack of venting of fuel tank, usually due to kinked vent hose.

[Chiefy]

A few questions:

Did you replace the vacuum line to the carb when you replaced the petcock?

Do you have a quick release connection on the fuel line?

Can you get it to recover by opening the gas cap when it starves at 85 miles? (That was was already asked.)

Do you have an inline filter?

Vac line was replaced a couple of months before the petcock.  I used the one from Redeye.  The vac line is about 14 months old, looks new, no cracking.

No quick release.

Have not tried opening the cap yet.

Yes, inline filter was installed by the dealer when he rebuilt the carbs about 6000 miles ago.  I don't know the brand/model.

There are no kinks or half loops in the fuel line.

[Willow]

A few questions:

Did you replace the vacuum line to the carb when you replaced the petcock?

Do you have a quick release connection on the fuel line?

Can you get it to recover by opening the gas cap when it starves at 85 miles? (That was was already asked.)

Do you have an inline filter?

Vac line was replaced a couple of months before the petcock.  I used the one from Redeye.  The vac line is about 14 months old, looks new, no cracking.

No quick release.

Have not tried opening the cap yet.

Yes, inline filter was installed by the dealer when he rebuilt the carbs about 6000 miles ago.  I don't know the brand/model.

There are no kinks or half loops in the fuel line.

Try opening the cap.  Obviously you'll need a spare key.  If that causes the fuel to flow it will indicate a plugged or kinked vent line, or, at any rate, a problem with the venting of the tank.

Inline filters can occasionally become an issue if they begin to restrict flow.  Switching from on to reserve changes the amount of fuel above the exit from the tank, theoretically altering the pressure on the fuel line.   

[Chiefy]

What I have to say is a summary of and in agreement with everyone above except Valky1500, who must be talking about the valve on a different motorcycle.  Possible causes for your symptom, all of which will get worse as you burn fuel and thus reduce the fuel pressure (hydraulic head):
1. Fuel restriction due to
     1.1. Clogged or undersized aftermarket fuel filter.
     1.2. Clogged screen inside the fuel tank.
     1.3. Kinked fuel line.
     1.4. Vacuum function on fuel valve not opening all the way due to
            1.4.1. Tear in vacuum diaphragm.
            1.4.2. Leak in vacuum hose.
2. Lack of venting of fuel tank, usually due to kinked vent hose.

I don't think the screen is clogged, but I don't know that either.  I have an aftermarket in line fuel filter.   I think I'll try removing it for awhile to see how it goes.  Fuel line not kinked, and no low point in the line.  Vac line looks fine.

There has never been a vent line on my bike since I've owned it.  Just the nipple on the bottom of the tank.

[BradValk48237]

Answer... Cover set...

I replaced my cover set right after I got the bike in 09.... after all I read here it scared me and I thought I would do a little preventative maint..... should have left it alone...

Last summer, the bike would get down to about 1/3 of a tank left and start to starve for fuel.... even when I switched to reserve........ left me by the side of the road once... for about 15 minutes til it started again and got me to a gas station.....

Got home and after talking to the fine fellows on here, I ordered another cover set and guess what.... the diaphragm had a tiny wear/tear/hole in it near the center crease where the spring went. As soon as I replaced it...no problems since.

I think that some of the problem may be with the diaphragms themselves..... they all seem to wear in the same spot of area and tear... they are pretty thin and that is where the spring rubs...

Some of them may just come with a weak spot because they are so thin.... rubber coated nylon fabric.......

If Mother Honda would just sell the diaphragm alone, I would be more than happy because the cover set is $35 buck and it is the only part that really needs to be replaced and all the other parts are fine......

Order a couple of cover sets or go to Pingle

I have one in the saddle bag now, so it probably wont happen again.. ANd I should have left it alone to begin with!!!

Brad

[Blackduck]

If the spring is rubbing on and wearing through the diaphragm you are missing a part.
The spring sits on a plastic disc.
As said before, if stuck on the road you can move the spring to the inside and turn the petcock into a manual only unit
But it is a good place to start looking.
Changing from main to reserve will not change the hydrostatic head, just allows fuel to flow from a lower point in the tank.
Cheers Steve

[Brian]

My 97 allows a small amount of gas vapors to escape through the key hole.I would think that this would also help to keep the tank from going slightly negative. I would suggest going pingel. I did and no problems even using the in-line Wix filter from NAPA.

[Chiefy]

My 97 allows a small amount of gas vapors to escape through the key hole.I would think that this would also help to keep the tank from going slightly negative. I would suggest going pingel. I did and no problems even using the in-line Wix filter from NAPA.

Did you have the same problem I described?

[registbass]

my wifes bike had this same problem, it was caused by the lower part of the screen in the petcock being plugged up with some clear gunk . after the fuel level dropped down to the level of the "blockage " it acted like it was out of gas . I cleaned the screen and it fixed it .

[cajundood]

Haven't changed the oem on my 98 standard since new. I never shut off the fuel since it is broken...basically always on reserve... . Soooo.....i figured i'd better nip this lil problem in the bud, before something decides to leak. Checked on a pingle...nah (waay too pricey) I found this one on ebaay for $29 shipped. should work and fits my budget too.....

[Brian]

My 97 allows a small amount of gas vapors to escape through the key hole.I would think that this would also help to keep the tank from going slightly negative. I would suggest going pingel. I did and no problems even using the in-line Wix filter from NAPA.

Did you have the same problem I described?

No sir. My valve was leaking in the off position, after reading everything here about hydrolocking I just got rid of the OEM replacing it with the manual pingel verses going thru the rebuilding process. No more worries now.

[Chiefy]

My 97 allows a small amount of gas vapors to escape through the key hole.I would think that this would also help to keep the tank from going slightly negative. I would suggest going pingel. I did and no problems even using the in-line Wix filter from NAPA.

Did you have the same problem I described?

No sir. My valve was leaking in the off position, after reading everything here about hydrolocking I just got rid of the OEM replacing it with the manual pingel verses going thru the rebuilding process. No more worries now.

I have no problem replacing it with a Pingle.  I just hate throwing parts willy-nilly at a problem.  Next few days are busy.  But I intend to replace (or perhaps temporarily remove) the in-line filter, check the petcock screen, and pop the fuel cap open when it happens again.  If I can at least rule those out, it tends to leave the petcock.  Fuel lines are not kinked.

[BF]

chiefy.....

Have you figured this out yet?  My bike has just starting doing the exact same thing.  Somewhere around 80 miles or so, it seems to starve for fuel and I've got to go to reserve.  I'm only replacing about 2 1/2 gals of gas or less when this happens. 

It's done it a couple times now at about the same 80 mile mark just tooling 'round town and going back and forth to work, but today doing two up and alot of 65 mph riding, it did it at about 60 miles. 

My OEM petcock is about as old as yours and has about as many miles on it too.  I'd hate to buy a new petcock, but I will if I have to to get this cured.  Other than this, but bike runs like a top. 

[Chiefy]

No, mine seems to have gone back to normal.  I've been keeping a spare key in the gas cap to open when it starts, but the problem stopped.  I'm guessing I don't have a vent issue, especially since I never had a vent hose on the nipple on the bottom of the tank anyway.

Since we both have fairly new valves, my gut feeling is that we each got one out of a bad batch.  I'm not sure what I'm going to do at this point.  I have an in-line fuel filter.  I'd like to remove it for awhile to see if it's restricting flow.  But it's a real pain to get to, and I don't enjoy wrenching.  If that doesn't effect it, maybe I'll turn the stock petcock into a manual and install a Dan Marc.    

Let me know if you make any headway with yours.  My old petcock never went over 90 miles to reserve.  The new one was going about 10 tanks to around 125 miles, and one tank low at 85 miles.  Then it happened a number of times in a row, which caused me to write that post.  Now 4 tanks normal again.  LOL what a pain.