Fuel Cap Breather

[darrsi]

Been looking around the internet and not found much, but was wondering if there's a  breather vent or hole that can be cleaned or poked on the fuel tank cap at all?

[joebloggs]

Been looking around the internet and not found much, but was wondering if there's a  breather vent or hole that can be cleaned or poked on the fuel tank cap at all?

Is the tank not vented from underneath, when I cut the bottom of the tank out I seem to remember two brass/copper tubes connected from the bottom to the pressing that the fuel cap bolts to, I guess one is the overflow and the other the vent.

[sc0ttie]

The hole under the fuel cap on mine got clogged a couple of months ago, cleaned it out with a long bit of single core wire and blew down it using a drinking straw. Not sure if that is what you mean though.

[darrsi]

I know there's a hole that goes from the top of the tank to the bottom vent underneath, but was wondering if there was anything in the cap at all that could need a clean.
To be honest it doesn't really matter now, i just found a shiny brand new one for £20 so thought i'd tart the bike up a bit as the old one looks so grubby.
It'll mean another key but i'm not really bothered about that. 

[fazersharp]

I know there's a hole that goes from the top of the tank to the bottom vent underneath, but was wondering if there was anything in the cap at all that could need a clean.
To be honest it doesn't really matter now, i just found a shiny brand new one for £20 so thought i'd tart the bike up a bit as the old one looks so grubby.
It'll mean another key but i'm not really bothered about that. 

Now i do like shiny - but what is so bad about the old one, wont it clean up

[darrsi]

[quote author=darrsi link=topic=21819.msg252280#msg252280 date=1486825252]
I know there's a hole that goes from the top of the tank to the bottom vent underneath, but was wondering if there was anything in the cap at all that could need a clean.
To be honest it doesn't really matter now, i just found a shiny brand new one for £20 so thought i'd tart the bike up a bit as the old one looks so grubby.
It'll mean another key but i'm not really bothered about that. 

Now i do like shiny - but what is so bad about the old one, wont it clean up
[/quote]


Just looks old and a bit battered, and £19.99 delivered is not exactly breaking the bank.

[fazersharp]

[quote author=fazersharp link=topic=21819.msg252281#msg252281 date=1486825960]
[quote author=darrsi link=topic=21819.msg252280#msg252280 date=1486825252]
I know there's a hole that goes from the top of the tank to the bottom vent underneath, but was wondering if there was anything in the cap at all that could need a clean.
To be honest it doesn't really matter now, i just found a shiny brand new one for £20 so thought i'd tart the bike up a bit as the old one looks so grubby.
It'll mean another key but i'm not really bothered about that. 

Now i do like shiny - but what is so bad about the old one, wont it clean up
[/quote]


Just looks old and a bit battered, and £19.99 delivered is not exactly breaking the bank.
[/quote]
This is what I would do

Drop allen key on tank - and chip tank.
Drop old filler on tank - bigger chip.
Drop new filler on floor - and bust it
Put old filler cap back on.
Spend 1 hour looking for the last bolt that the garage fairies have hidden.
Think - well that was a good 3 hours and 19.99 spent.
On top of that its now raining and I could of spent that 3 hours out on the bike

[Fazerider]

This is what I would do

Drop allen key on tank - and chip tank.
Drop old filler on tank - bigger chip.
Drop new filler on floor - and bust it
Put old filler cap back on.
Spend 1 hour looking for the last bolt that the garage fairies have hidden.
Think - well that was a good 3 hours and 19.99 spent.
On top of that its now raining and I could of spent that 3 hours out on the bike

    :lol      :lol      :lol
I've had days like that too.

[darrsi]

[quote author=darrsi link=topic=21819.msg252283#msg252283 date=1486826718]
[quote author=fazersharp link=topic=21819.msg252281#msg252281 date=1486825960]
[quote author=darrsi link=topic=21819.msg252280#msg252280 date=1486825252]
I know there's a hole that goes from the top of the tank to the bottom vent underneath, but was wondering if there was anything in the cap at all that could need a clean.
To be honest it doesn't really matter now, i just found a shiny brand new one for £20 so thought i'd tart the bike up a bit as the old one looks so grubby.
It'll mean another key but i'm not really bothered about that. 

Now i do like shiny - but what is so bad about the old one, wont it clean up
[/quote]


Just looks old and a bit battered, and £19.99 delivered is not exactly breaking the bank.
[/quote]
This is what I would do

Drop allen key on tank - and chip tank.
Drop old filler on tank - bigger chip.
Drop new filler on floor - and bust it
Put old filler cap back on.
Spend 1 hour looking for the last bolt that the garage fairies have hidden.
Think - well that was a good 3 hours and 19.99 spent.
On top of that its now raining and I could of spent that 3 hours out on the bike
[/quote]


Got a tank cover on there now, so just the cap that's exposed.
I must say it feels much nicer now, the padding gives a better grip and i noticed a big difference in warmth as well not having the legs touching bare metal.

[darrsi]

The hole under the fuel cap on mine got clogged a couple of months ago, cleaned it out with a long bit of single core wire and blew down it using a drinking straw. Not sure if that is what you mean though.

I just tried using compressed air to blow down the air vent hole in the actual fuel tank and it didn't sound like anything was going through, but in fairness i couldn't see what size the hole is because of the rubber housing which surrounds it?
Which also makes me wonder how that hole can get clogged in the first place when it looks fairly protected?

[locksmith]

I suppose the obvious question is what makes you think it's blocked?

[Oldgit]

Canny Pee.

[darrsi]

I suppose the obvious question is what makes you think it's blocked?

Still getting the occasional starting issues, just a process of elimination.
Used a can of air at first, then popped by work to pick up a parcel then used a proper airline.
Read that extreme weather can cause issues if the tank isn't vented properly, as in very hot or very cold.
Got a new cap on the way but as i can't determine what the vent hole looks like due to the rubber part surrounding it, it was a bit of an unknown if it's right or not.
Blew air through the tiny cap hole underneath and i could feel air coming out of the cap mechanism so that's probably okay.

[locksmith]

As a lay-man, I would think a blocked breather would cause the tank to gain a negative pressure so that when you open the filler cap a loud hiss of air rushing in would be apparent. Is that the case?

[darrsi]

As a lay-man, I would think a blocked breather would cause the tank to gain a negative pressure so that when you open the filler cap a loud hiss of air rushing in would be apparent. Is that the case?

I think if it was totally blocked it would do that, but if it was that bad it would also run like shite or even cut out.
Once it's started, eventually, it appears to run okay though. I'm mainly only doing 6 mile runs to and from work so it may not even be far enough to build up a big vacuum.
To be honest, i'm just trying everything, one thing at a time, until i figure it out.
I might try blowing air up from the bottom of the tank which will be easier to feel if it's blocked or not. I can't see why it should be though as it all looks like a sealed unit once the cap is locked down.

[fazersharp]

[quote author=locksmith link=topic=21819.msg252499#msg252499 date=1487063361]
As a lay-man, I would think a blocked breather would cause the tank to gain a negative pressure so that when you open the filler cap a loud hiss of air rushing in would be apparent. Is that the case?

I think if it was totally blocked it would do that, but if it was that bad it would also run like shite or even cut out.
Once it's started, eventually, it appears to run okay though. I'm mainly only doing 6 mile runs to and from work so it may not even be far enough to build up a big vacuum.
To be honest, i'm just trying everything, one thing at a time, until i figure it out.
I might try blowing air up from the bottom of the tank which will be easier to feel if it's blocked or not. I can't see why it should be though as it all looks like a sealed unit once the cap is locked down.
[/quote]
Have you tried taking it out for a dam good thrashing

[darrsi]

[quote author=darrsi link=topic=21819.msg252507#msg252507 date=1487069348]
[quote author=locksmith link=topic=21819.msg252499#msg252499 date=1487063361]
As a lay-man, I would think a blocked breather would cause the tank to gain a negative pressure so that when you open the filler cap a loud hiss of air rushing in would be apparent. Is that the case?

I think if it was totally blocked it would do that, but if it was that bad it would also run like shite or even cut out.
Once it's started, eventually, it appears to run okay though. I'm mainly only doing 6 mile runs to and from work so it may not even be far enough to build up a big vacuum.
To be honest, i'm just trying everything, one thing at a time, until i figure it out.
I might try blowing air up from the bottom of the tank which will be easier to feel if it's blocked or not. I can't see why it should be though as it all looks like a sealed unit once the cap is locked down.
[/quote]
Have you tried taking it out for a dam good thrashing
[/quote]


Not sure what purpose that would serve, it's a starting issue, not a running one.

[darrsi]

The K&N air filter was cleaned not so long ago, and if you speak to my work receptionist she'll definitely confirm it's getting petrol by the way it has backfired in the past letting out a flame like a jet planes afterburner and a noise like an elephant gun.
The battery is good, that consistently supplies power when it's trying to start, without any signs of pegging out, it's just that the engine doesn't want to catch.
Quite a few times it's started for about a second or two, then just cut out, then it takes about another 2 minutes of trying to start it, with and without the choke before it will eventually catch and run as if there was never a problem.
But thinking back it's always misbehaved in hot summer or in cold winter evenings after work, which is what led me down the blocked air vent path.

[fazersharp]

[quote author=fazersharp link=topic=21819.msg252508#msg252508 date=1487070890]
[quote author=darrsi link=topic=21819.msg252507#msg252507 date=1487069348]
[quote author=locksmith link=topic=21819.msg252499#msg252499 date=1487063361]
As a lay-man, I would think a blocked breather would cause the tank to gain a negative pressure so that when you open the filler cap a loud hiss of air rushing in would be apparent. Is that the case?

I think if it was totally blocked it would do that, but if it was that bad it would also run like shite or even cut out.
Once it's started, eventually, it appears to run okay though. I'm mainly only doing 6 mile runs to and from work so it may not even be far enough to build up a big vacuum.
To be honest, i'm just trying everything, one thing at a time, until i figure it out.
I might try blowing air up from the bottom of the tank which will be easier to feel if it's blocked or not. I can't see why it should be though as it all looks like a sealed unit once the cap is locked down.
[/quote]
Have you tried taking it out for a dam good thrashing
[/quote]


Not sure what purpose that would serve, it's a starting issue, not a running one.
[/quote]
Your bike is bored with the 6 mile commute, its fed up, I promise you, give it a blast and the next time you come to start it will  going before your thumb has even touched the button. 

[His Dudeness]

Next time it happens take a plug out and check if it's sparking and what condition it's in if it's wet etc