crank case breather

[askinmechanic]

hello all, what is the benefit of utilising a breather and catch tank, i have seen them on loads of bikes but not sure what advantage it gives or is it just asthetics ?

[Kryten]

Now some one will correct me if I'm wrong, but....


engine breathers are usualy routed into the Airbox Plenum chamber so that the oil vapours produced by the engine are drawn through to the combustion chamber and burnt. This was early on in emmissions control technology.

Old brits, and yankee stump pullers allowed crankcase pressure to vent through the crankcase and primary drive cover gaskets (Ducks for cover!)

As most performance modifications involve slinging the airbox, the breathers have to be routed somewhere. It always used to be to the back of the bike so the oil mist would obscure the number plate.

This was particulary useful if the engine had some significant performance mods (Big Bores, Hi comp pistons etc.), plus other benefits!

As racing regs caught up with safety and environment issues the race machines were no longer allowed to vent the breathers to the back of the bike so the catch tank was born. Any thing from Vidal Sasson bottles to Red Stripe Lager cans have been used. Of course somebody somewhere decided to make some with a bit more style and you now have loads to choose from.


So if you are binning the airbox and putting a big bore kit in place. Running the cam cover breather, and a second line from the oil filler cap to a catch tank, reduces crankcase compression and condenses the vapour for you to drain off every now and then, thus keeping the bike nice and shiney.




Jim

[johnr]

pretty much spot on. these engines like to breathe, pressure buildup in the crank cases can in extreme cases damage gaskets and cause oil leaks and in a small way, sap power. breathers , particularly on big bore engines can help to reduce this. personally i like the guinnes can zip tied to the frame but im not too much a believer in bling, though there are several aftermarket breather kits available.

[nokatanayet]

i think later on some bikes had a problem due to higher pressure building up in the engine and when they stuck it on the back wheel it dumped oil straight out onto the back wheel etc

[askinmechanic]

well thank you very much for that info, so it has a real benefit if you have engine mods but its just a bling thing on an unmodded bike, my little pop up shall do without

[Pedda]

...and condenses the vapour for you to drain off every now and then...

I saw clever gits who made a chain oiler from there - avoids additional draining and is good for your cahin.