Fuel tank cap

[Oxygen]

I opened the fuel tank today after the first spin in a few months (march) and I really got a big blow out of air and vapour. First time this has happened. Normaly there is some pressure difference big this was quite noticeable.

Normal or not ?

[know your limitations]

Hot weather, low fuel, big whoosh. Sounds perfectly normal.
Think of all that lovely sunshine expanding those fuel vapours and then you let them out.


Don't fret.


But more importantly, while this fine weather continues, avoid filling your tank then just leaving it in the sun as there's even less space for those vapours to expand into.
If you're gonna fill it, do it before a big ride.
Got a garage or shady storage? Ignore everything I've said above (apart from the "don't fret" part) 

[red98]

if you`ve had the tank off recently it might be worth checking the breather pipes are not blocked or kinked....otherwise nothing to worry about 

[Fazerider]

No, it's not normal. The breather is blocked.
If you get a length of flexible plastic tube and press it against the little orange cone-with-a-hole that's visible when the filler cap is open, you should be able to blow down the breather tube and hear it exiting at the rear of the engine. Blockage is usually due to the rubber hose at the bottom of the tank getting pinched somewhere.

[Dead Eye]

I'd go with Fazerider on this one. Double check the breather hoses underneath the tank - there shouldn't be any real pressure build up in the fuel tank. If this is occuring its likely you're getting low pressure after a long ride on a cool day and that can lead to fuel starvation...

It's a quick job, and the idea of poking something down the breather tube is probably a good idea, just dont use anything too sharp

[ElkWorks]

i better check mine then, i get a right vaccuum effect trying to release the fuel cap, but i dont leave it around, i do 80 miles a day on it 

[Oxygen]

Turns out it was a kinked breather pipe. I just pulled them through at the bottom to straighten them up.

[del30]

You know when you pulled from the bottom where abouts did you pull it?
Mines suffering the same problem?

[Dead Eye]

I tend to feed mine to the right of the bike, down past the carbs and to the floor passed the clutch cover

[darrsi]

Breather pipe, without a doubt.........

[del30]

When I first got my bike the breathers wernt connected then when my carbs were stripped and cleaned  the breathers have been refitted, is there any chance they can be refitted the wrong way round?

[Dead Eye]

Doesn't make any difference as they are both hollow pipes that are open to the outside air

[Deefer666]

Only early FZSs have the those pipes after a while they changed them and there is a kind of rubber funnel under the tank going off into 2 pipes to save you from kinking the pipes as you put the tank down.