Purpose of breather hose from top of engine?

[Tom R]

Sorry to hijack this thread. Reading he replies, my question is: is there any benefit (except environmental) to having the breather hose attached to the air box, instead of just being disconnected?

The vapors can make a mess of everything over time. Since my bike doesn't have an airbox, I run my vent tube into a catch can, but I used to run it down behind the engine as a road draft tube.

[J2Bs]

Disconnected and what, capped? Post #2 mentions the pressure build up in the engine. That pressure build up has been mentioned in other threads as a possible cause of oil leaks elsewhere on the engine.

when I got the bike the hose was connected to the engine, just not the air box. Engine an still breathe fine, just wondering if to add the hose also to the air box or just let it roam free!

[J2Bs]

The vapors can make a mess of everything over time. Since my bike doesn't have an airbox, I run my vent tube into a catch can, but I used to run it down behind the engine as a road draft tube.

Thanks Tom. Helpful insight.

[Burque73]

The vapors can make a mess of everything over time. Since my bike doesn't have an airbox, I run my vent tube into a catch can, but I used to run it down behind the engine as a road draft tube.

Did you use a hose with a pinched end on it like the one under the airbox? Just curious is all.

[JTGS850GL]

Sorry to hijack this thread. Reading he replies, my question is: is there any benefit (except environmental) to having the breather hose attached to the air box, instead of just being disconnected?

There is a slight negative pressure in the air box that assists in scavenging. Makes the ventilation system more efficient and provides better ring sealing.

[Steve]

Sorry to hijack this thread. Reading he replies, my question is: is there any benefit (except environmental) to having the breather hose attached to the air box, instead of just being disconnected?

MY question is ... how can you hijack a thread that has been DEAD for five years?

Yes, the main benefit is environmental, the other benefit is that the oily vapors that come through that port on top of the engine get taken somewhere other than just collecting on the engine, frame and bottom of the fuel tank. Whether you run it to a catch can or simply run a long tube down below the swingarm pivot as a road draft tube is up to you.

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[Gorminrider]

maybe you are using the search function to answer questions..good for you! Many don't bother.

I might have missed it but didn't see anyone mentioning that a fair amount of water moisture might be being removed from the engine oil as steam this way,...

I guess you are going to put "pods" on and get rid of the airbox...? The hose might be mentioned in one of those threads too, per what they did with it. I've heard of people putting it into a jar (vented to atmosphere of course) but I don't think the suction that the original sytem has would be there.

[Burque73]

I've seen a couple pod conversions that have filters on the end of the hose. One on a GS 750 and another on a KZ 1000. They used something like this. I'm not saying to use this, just commenting on what I've seen.



I don't understand how that kept oily junk from coming out though.

[hannibal]

I guess it works as a reverse filter so the oily mess gets trapped on the inside. With that said, I left the breather hose open to the air above the trans case.