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Tank Breather
The Doc - 11/9/07 at 09:09 PM

I have not added a breather to my tank/filler tube. Seem to remember years ago that venting was achieved by a tiny hole in filler cap, or similar.

So far no 'vacuum' in tank related problems. I guess the cap must be sucking in a little air as there are no leaks when full to brim. Is this an SVA issue?

Ta

dave1888 - 11/9/07 at 09:15 PM

I used one of these.

http://cgi.ebay.co.uk/KTM-Motorcycle-SXS-Fuel-tank-cap-vent_W0QQitemZ250161259712QQihZ015QQcategoryZ108833QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Edited on 11/9/2007 by dave1888]

RazMan - 11/9/07 at 09:22 PM

Its not really an sva issue - as long as the tank doesn't leak they will be happy.
However you really ought to fit some kind of a breather - a powerful fuel pump can implode a fuel tank I once saw a Mini tank crushed like a beer can - quite impressive.

nitram38 - 11/9/07 at 09:24 PM

quote:
Originally posted by RazMan
Its not really an sva issue - as long as the tank doesn't leak they will be happy.
However you really ought to fit some kind of a breather - a powerful fuel pump can implode a fuel tank I once saw a Mini tank crushed like a beer can - quite impressive.


If you use an injection pump with a fuel return it will also pump the tank up!
For fuel tank with a return, always use a two way valve that closes when inverted.
I bought mine from thinkautomotive.

DaveFJ - 12/9/07 at 08:34 AM

I have just fitted a vent to my ally tank. I thought long and hard to come up with a simple solution that did not involve removing my tank and asking someone to weld in a new boss...

I got the largest rivnut i could find and fitted it to the tank with a little fuel proof sealant. then drilled through the length of a suitably sized bolt and cut the head off. the now hollow stud was screwed into the rivnut again using sealant (also acts as thread lock) leaving enough protruding to attach a pipe to

I couldn't avoid a small amount of swarf getting into the tank but I removed the filler neck and put a hoover nozzle into the tank near where I was drilling so hopefully I have minimized that problem and the LP fuel filter should catch the rest

[Edited on 12/9/07 by DaveFJ]

nick205 - 12/9/07 at 02:45 PM

My MK tank is vented by way of a short length of hose connected to the breather (or return) pipe which exits on the top of the tank. The hose is the P clipped to the chassis so theat the open end finishes below the bottom of the tank. That way the tank can vent and if it were to end up upside down, the fuel would stay in the tank.

Engine set up is a carb'd ointo with mechanical fuel pump and no fuel return line.