Tank Vacuum problem ( I think !! )

[leevtr]

I think I have a problem with my 19 Litre tank, and I believe it to be air vacuum related ( for want of a better word ).

Bike runs fine for 5 mins or so, then starts to miss, cough and splutter, bit like theres a fuel starvation problem. When it happens I just have to open the fuel filler ( doing it on the move, not a good idea ) and its cured, till next time. If I kill the engine without opening the fuel cap it still splutters. Have double triple checked all the lines, nothing there to indicate a problem, and when you gun it she pulls like a train. The fuel cap is straight off my original tank, and was never a problem, so cant see why it would be that.

I know about blocking off the old vacuum hose for the fuel tap, so it aint that.

Any ideas ?

[Tweety]

Check breather hoses for kinks and bends... It indeed seems like you are getting back pressure in the tank, so those are the obvious culprits... Also, riding in wet weather, the ends benefit from being cut at an angle to make sure no drops of rain, or excess fuel gets caught there, by capillary force and blocks the line...

Could also be the vacuum pet rock, if the membrane is tired, it tends to slowly creep closed, and opening the tank "resets" it...

[leevtr]

Check breather hoses for kinks and bends... It indeed seems like you are getting back pressure in the tank, so those are the obvious culprits... Also, riding in wet weather, the ends benefit from being cut at an angle to make sure no drops of rain, or excess fuel gets caught there, by capillary force and blocks the line...

Could also be the vacuum pet rock, if the membrane is tired, it tends to slowly creep closed, and opening the tank "resets" it...

Checked breathers....in fact i Removed it to check it and havent re fitted it. ( whether that makes any difference ?? ) Ant its fitted with a varadero fuel tap, which is just an on/off affair.

[Wicky]

Check the hole just inside the filler cap neck of the tank - try giving it a blast of air to clear any muck in the breather.

[leevtr]

Check the hole just inside the filler cap neck of the tank - try giving it a blast of air to clear any muck in the breather.

TBH I thought that was the overflow ??

[agentpineapple]

I seem to remember benny saying you need to block off the breather pipe when using the 19ltr tank, I might be wrong tho....

[leevtr]

I seem to remember benny saying you need to block off the breather pipe when using the 19ltr tank, I might be wrong tho....

Think thats the vac pipe to the fuel petcock. Thats become a carb balancer now, and is plugged.

[lloydie]

Is you filler cap blocked ?
Do you get a hiss when you open it after it's cut out ?

[leevtr]

Is you filler cap blocked ?
Do you get a hiss when you open it after it's cut out ?

I did hear it once but to be honest I'm not able to hear it every time as the minute it starts surging I'm opening the cap while I'm going along, before its completely cut out. Filler cap is my original one and was perfect before.

[rollingthunderx2]

Isnt there a problem like this if you fill the tank right up, it causes an air lock?

[leevtr]

Isnt there a problem like this if you fill the tank right up, it causes an air lock?

Well, supposedly yes, but in 3 storms and 40,000 miles of brimming every time, I've never once had a problem. I did think of this when it first happened earlier, just after I filled, so I kept riding to burn some fuel off. Got through a good gallon but problem still there.

[lloydie]

Sound ms like the filler cap breather is blocked . It's where you put the key

[darkember]

Isnt there a problem like this if you fill the tank right up, it causes an air lock?

Well, supposedly yes, but in 3 storms and 40,000 miles of brimming every time, I've never once had a problem. I did think of this when it first happened earlier, just after I filled, so I kept riding to burn some fuel off. Got through a good gallon but problem still there.

Agreed but is this the first 19 liter tank you have had & is it an add-on mod to your normally 16 liter machine?? If this is the case have you used the full 19 Liter setup ie the external petcock arrangement that sits behind the tank??

[agentpineapple]

so what your saying is, lee's got a 19ltr tank but can only fill it with 17ltrs........

[leevtr]

Isnt there a problem like this if you fill the tank right up, it causes an air lock?

Well, supposedly yes, but in 3 storms and 40,000 miles of brimming every time, I've never once had a problem. I did think of this when it first happened earlier, just after I filled, so I kept riding to burn some fuel off. Got through a good gallon but problem still there.

Agreed but is this the first 19 liter tank you have had & is it an add-on mod to your normally 16 liter machine?? If this is the case have you used the full 19 Liter setup ie the external petcock arrangement that sits behind the tank??

Sits behind the tank ????????

No idea what thats all about. Its got a varadero fuel tap fitted, which is just a straight on/off switch.