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Discussion Starter · #1 ·
Just had my airbox off to change spark plugs and air filter, so decided to check if breather hoses are OK. I've blown though both, the straight one flows freely, one with valve - flows when blown, stops in reverse direction. :confused:
In many posts here there is opinion that this one is allowing air to be sucked into tank to prevent vacuum, but valve seems to be working in the opposite direction. Yes, I've checked that valve is mounted with UP arrow correctly and valve inside moves freely when shaken. Anybody has an explanation?

By the way, I have experimentally determined that tank breather (with valve) goes on the inside nipple, while water drain goes to the outside one (closer to the side of bike). I just blown the air to the holes in the tank filler to find out. This is '07 with plastic tank.
 

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What position did you hold the valve at when you tested it? It has to be close to vertical to work right. If at an angle or horizontal it will shut off. Valve should flow both ways or otherwise on a hot day it will result in expanded & deformed tank.

On 08 onwards bikes it is mounted very close to the tank nipple in order to ensure it stays at correct angle. On older bikes it was further down on the tube which often resulted in valve ending up in an angle and causing vacuum probs.

I have taken the valve out on both my 1050s. It is much more hassle than it is worth.
 

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Discussion Starter · #3 ·
Valve hanging freely on tube -> vertical.
So it is supposed to flow in both directions... Maybe I used too much air pressure on the intake side. When I shook the valve while blocked, it would let the air flow, so maybe this is explanation.
Thanks, Martin.
 

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So it is supposed to flow in both directions...
That is my understanding. If it would not let tank breath out that would be as problematic as not letting tank breath in.

The valve is also listed in schematics as "tipover valve", so seems that it is more than a simple one-way-valve.
 
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