Breather tubes

Message

wickedrider · Mon Oct 29, 2007 12:47 pm

What's the purpose of breather tubes?

slimcolo · #2 Unread post by **slimcolo** » Mon Oct 29, 2007 12:58 pm

They vent the cam cover under the generator. This directs any blow-by on to the ground instead of blowing oil on the engine. Cars had the same thing before our Government required PCV valves. It is also known as direct crankcase ventilation.DCV

Tube, Breather oem 24912-52tb (for an XL)

wickedrider · Mon Oct 29, 2007 1:18 pm

Thanks, slimcolo

Sev · #4 Unread post by **Sev** » Mon Oct 29, 2007 1:45 pm

Uhhh, it vents some other places, basically it's to relieve pressure anywhere that it could potentially vent - crankcase, final drives, there's a couple of different places.

wickedrider · Mon Oct 29, 2007 1:53 pm

Thanks Sev. OK, so here is the real issue. I removed the gas tank from my 750 Spirit yesterday. I saw the place where the tube attaches to the gas tank. However, there was no tube. Just wondering what that meant and whether it was mandatory for me to get one before I replace the tank.

slimcolo · #6 Unread post by **slimcolo** » Mon Oct 29, 2007 2:07 pm

Didn't understand what you meant by breather tube before. Your last post to Sev cleared up what exactly you meant. (I think a pic next time)

Thats probably a vent/overflow tube and will leak gas directly out especially w/ a full tank. Best to replace tube, a lot cheaper than fixing bike after it catches afire.

wickedrider · Mon Oct 29, 2007 2:12 pm

What kind of overflow? The connection is on the bottom of the fuel tank. Could the blow by be getting blown into the air filter area?

mydlyfkryzis · Tue Oct 30, 2007 3:46 am

The crankcase vent and the fuel tank vent are different things.

Sev described the crankcase vent or breather.

The fuel tank vent/breather is different. It vents the tank. the connection may be on the bottom, but internally, it probably has a tube to the top of the tank. This vent should have a line to the ground. If your fuel tank is overfilled, or heat causes the gas to expand, the overflow comes out of this breather. You want a tube on it so gas doesn't hit a hot engine.

flynrider · #9 Unread post by **flynrider** » Tue Oct 30, 2007 9:46 am

The tank vent actually serves two purposes. It allows the overflow to escape (relatively safely) in the event that the tank is overfilled, or the fuel expands. In the other direction, it allows air to enter the tank to replace fuel that has gone to the engine.

The second function is critically important. A gravity feed fuel system won't deliver fuel unless you replace the burned fuel in the tank with air. The bike will eventually stall. An even worse case is with fuel pumps. The pump will continue to pump out the fuel and the (much stronger) vacuum can cause the tank to implode.