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Old 08-18-2012, 08:00 PM   #10
JRWooden
Beastly Adventurer
 
Joined: Jul 2008
Location: The great state of confusion
Oddometer: 4,112
Ok ... long day here so don't flame me if I hose this up eh?

If the fuel tank is suffering from high VACUUM than yeah ... likely it is a clogged canister and maybe a messed up check valve to go with that ................

If there is high PRESSURE in the tank that likely is not the canister's fault.
While only USA (maybe Canada I don't recall) bikes have a canister,
all bikes have the pressure/vacuum check valve in the vent line which could freeze or become plugged and cause too much pressure in the tank ... overfilling or topping up and adding road heat can cause this as well.

Sometimes it is hard to tell when opening the tank if pressure is venting or vacuum is being releived...
hold a piece of paper up next to the tank lid when you flip it and deflection will tell you...........

On early models the pressure/vacuum check valve is actually a ball-check as described above ... Joel mentioned that on later models it was actually a contraption with a sintered insert that was easily clogged.
The specifications for the valve (at least the older valve) as to how much pressure/vacuum they would hold before venting were pretty high....

I am personally not convinced that the CC is the reason USA bikes have cracked fuel tanks far more often than non-USA bikes... I'm not saying that the CC is NOT to blame I'm just not convinced..... that topic has been kicked around multiple places also ...

Just my $0.02...
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