More engine & gearbox life ..... breather hose! READ THIS !

[John Orchard]

I've been amazed how quickly gearbox oil become dirty, after 40 years I realize that the breather hose vents down under the engine just the front of the rear wheel, possible the dirtiest area known to man!

So now I either fit an in-line fuel filter to the end of the hose, or put the end of the hose into a block of oiled, sponge foam, and place it in a less dirty part of the bike.  This is surely going to stop dust getting into the gearbox,  I reckon this would have to give 10 times better life to the internal components.

While stripping my modern RMZ450 one day, I found the engine breather hose vented to exactly the same place as above !!!!  What is Suzuki trying to do to owners of their bikes?!!!  A 4-stroke is going to breathing quite heavily in & out of that breather, sucking in a huge amount of dirt !!!!  My RMZ now runs a hi-flow fuel filter on the end of the hose, and breathes from under the tank, not down at the rear wheel.

Why the hell would anyone just bother cleaning airfilters when heaps of dirt gets in through vent hoses?

[Tim754]

On my sidecar engines John, I have re routed the breather tubes to inside the air filter box, same as most cars

[Slakewell]

If you vent to the airbox make sure water can not get in.

[John Orchard]

Venting the hose to the airbox aint going to help very much; how dirty does an airfilter get. The hose must have a filter attached for any real benefit.

[jimson]

Thanks for your input on this. I will look at all of my bikes & address the situation.jimson

[Tim754]

Yes I have inline moisture filtering Of course the outlet exits pre air filtering... all access points have oil and fuel proof grommet and silicon sealing, and all hose tubing is routed , guided and cable tied to avoid kinks,crushing and splits.

If your air filter is being covered in obvious oil residue or sludge from your engine/gearbox breather hose   umm   you may have a problem or three needing review there.....

If your air filter is just dirty......

[OverTheHill]

can you connect it into the aircleaner so it breaths through the filter from within. Not sure it would matter [huffing & blowing], if you dropped it you may get some oil escaping but may only wet the filter a bit more. Not quite relevant but back in the RD400 days their air bleed to the needle jet [emulsion tube] was from a separate hoses plugged into the air filter element, breathing from within. No idea why they did that in those years. Anyway--clutch linings [someone said] can dis-colour the oil, me thinking two strokes but why not all, plus blow by on 4/ if she's getting a bit tired.

[FourstrokeForever]

Yes, the clutch plates are the biggest factor in dirty engine oil. The pulses on a fourstroke as it breathes in and out are so fast that it is very unlikely that any "dirt" will get into the motor, unless the breather hose is so short that the dirt can get there in a hurry. Still, re routing to a higher place like under the tank or somewhere else high is a good idea. Even better with a filter at the end.

[211]

on my Velocette i had as much crankase compression as combustion and couldnt keep a gasket in the thing so I vented the engine at the rocker box and used a Ford PCB? valve on the end of the vent line - motor ran better, lot less oil leaks. Im sure there are guys out there who know a lote more about this than me and I wonder if the modern engine vent is there for similar reasons?
211

[FourstrokeForever]

It's a PCV valve Dave. And yes, venting the engine does help keep crank case pressure down. It's a well known fact the the better an engine breathes, the more free it will run. I had oil blow by on my Beezas until I also put breathers at the rocker boxes. No more oil leaks 

[KTM47]

Would the little plastic one way valves that can be sometimes found in fuel tank breather hoses do the job?

[alexbrown64]

There must be something in using a Positive Crankcase Valve, as in the case of a car, if you have a blocked one, your car can run like shit, so i guess in certain cases, this could hold true for motorcycles as well.  You would think that the little piece that comes out of your case for the breather tube to attach to would be a 1 way valve.  Perhaps they were worried about these getting blocked all the time and creating running issues.  Could be a good little after market item here.
Cheers,
Alex

[mick25]

I run a filter system on my breather hose , I got it from super cheap auto it has a foam filter and a stainless screen in it , I oil the filter like the air filter foam it works great but they don't sell them anymore.
A bit more on gear box life what I do.

On my TT500 it has magnets glued in the removable sump this picks up the slightest of metal paste from gear wear etc .

I also came up with a theory on new oil and whats in it being dark in colour and spotting foreign objects in it , there shouldn't be anything in it but oil  .
 I use a funnel with a very fine stainless steel screen in it with a magnet in it to filter the new oil when I do oil changes etc.
might sound a bit paranoid but better safe than sorry.

[PEZBerq]

Mick
Filtering new lube and hydraulic oil from the suppliers drum or container is best practice in industry. There is a reason they often use black containers!

[Rossvickicampbell]

yeah - try gaining compliance with CAT 5 star for lubricants!!!