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Crankcase breather

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jchesshyre
the 900
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Posts : 633
Location : Chester

Crankcase breather

Post by jchesshyre on Sun 06 Sep 2015, 2:55 pm

As we know, every 4000 we're supposed to pull the plug out of the bottom of the crankcase breather hose to allow any 'deposits' to drain out. 

On my last CB, which I got with 24,000 miles on it and retired it at 145,000, there was always a little trickle of oil that came out when I did this. As the miles racked up, the amount that came out increased a tiny bit. 

On my current bike, which I got at 13,000 miles and now has 46,000, every time I pull this plug out there's been absolutely nothing to drain out. Not even a trace of oil. 

Why might this be? As far as I know, oil mist from the valve cover gets sucked gently into the airbox and any that condenses in there trickles to the bottom and collects at the foot of this hose. Correct me if I'm wrong. 

I've just tried blowing on the end of the hose where the plug goes and it's free of obstructions, as is the hose between the valve cover and airbox. Could it be that my previous bike hadn't been broken in as well and had a lot more blowby into the airbox, whereas this one doesn't? It's mysterious. Obviously if it's fine then I'm pleased that I have a good engine on my hands (after all, when I did retire the last one it was due to excessive oil consumption, though I couldn't complain after the miles it had done) but if it's collecting somewhere that it shouldn't then maybe I should investigate further...

What's anyone else's experience with this hose and its deposits? Obviously I've done a lot of miles but only have one bike to compare with.
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arrison
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Re: Crankcase breather

Post by arrison on Sun 06 Sep 2015, 6:44 pm

I've never taken mine off, but this got me curious so I did. I but the bike with 24k on it, it's now at 38k,and there was nothing in mine either
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Flyingbrick
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Location : Lower Saxony, Germany

Re: Crankcase breather

Post by Flyingbrick on Sun 06 Sep 2015, 7:25 pm

It depends on the way you're riding. If your average distance is ten miles and up, you won't find much fluid, if you find something at all. But some short distance riders got quite a lot condensate not only in the outlet tube of the airbox but in the breather tube coming from the valve cover as well.

"Christine", my '95 CB500R, was bought from a lady who rode only short distances and didn't made any maintenance. The breather tube was full of white condense, the engine oil was soaked with water and the airbox was damp inside. These are the bikes that need an periodic inspection, not those with proper maintenance and frequent usage.


Last edited by Flyingbrick on Sun 06 Sep 2015, 7:45 pm; edited 1 time in total
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jchesshyre
the 900
the 900

Posts : 633
Location : Chester

Re: Crankcase breather

Post by jchesshyre on Sun 06 Sep 2015, 7:27 pm

I avoid short journeys at all costs, and did so on my previous bike. What I used to find in the tube wasn't really water, it was a small quantity (maybe half a teaspoon?) of engine oil.
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Flyingbrick
Four's a...something...
Four's a...something...

Posts : 168
Location : Lower Saxony, Germany

Re: Crankcase breather

Post by Flyingbrick on Sun 06 Sep 2015, 7:44 pm

That could be caused by some overfilled oil, I guess.
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badseeds
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Re: Crankcase breather

Post by badseeds on Sun 06 Sep 2015, 10:54 pm

Hmmm. Just to confuse things even more.... I do lots of miles on mine, 30k in the last 18 months and there's always a little bit of oil in that bung when I remove it at oil/filter changes (4k). The bike uses no oil and has covered 120k miles.

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Re: Crankcase breather

Post by Guest on Mon 07 Sep 2015, 11:52 am

When I cleaned this breather tube first time a thick tar-like substance came out thick as liquid honey.
After that nothing like that any more. Maybe first time ever it was opened in 30k kilometres.
  BTW: Engine oil stays really clear and have been doing about 2k kilometres with it.
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eternally_troubled
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Re: Crankcase breather

Post by eternally_troubled on Mon 07 Sep 2015, 1:40 pm

I get quite a lot out of mine. Not oil but a slimey gooey blackish substance plus a bit of white condensate.

I tend to do quite a lot of short journeys, so I kind of agree with Flyingbrick.
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stormbringer
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Re: Crankcase breather

Post by stormbringer on Tue 08 Sep 2015, 12:22 pm

I do my 2*8 miles daily + the errands around town during week, then in the weekends go on occasional rideouts. Some needed, some for the fun of it. Unplugging the collector hose twice a year gets me a few tar-like drops of black goo. I believe this is the expected result to get from the blowby-gas emitted.
Like @Werner Van der Straten I observe that my oil stays surprisingly clear and uncontaminated. And un-consumed... I'm always amazed at how these engines seem to consume no oil. Compared to your average car engine, the two-barrel Honda lump is somewhat high-strung yet demonstrates just how good mechanical engineering can be if you put your mind to it. Quality-wise, Honda sits in the absolutely opposite end of the spectrum compared to eg eastern-european mid-80's mechanics. Even better, it's hightech low-tech, if you know what I mean. No fancy wizardry or electronically based mumbo-jumbo to get at the result, just proper oldskool mechanics with little if no expense spared. Me likes that.
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jchesshyre
the 900
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Posts : 633
Location : Chester

Re: Crankcase breather

Post by jchesshyre on Tue 08 Sep 2015, 12:31 pm

Hear hear, and see my last post on the 'Improvements on perfection' topic where I air similar views!


So if I'm getting no residue whatsoever in the airbox drain tube, despite revving the tits off my engine much of the time (well, not abusively but keeping it between 6 and 9k much of the time, as we should), does this just mean I have a very well-run-in engine with minimal blowby?

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