I just recently noticed a crack in the airbox end of the crank case breather hose. Can anyone give me some information on what this hose does exactly and what symptoms Ishould be seeing because of this. My bike runs fine, I dont notice any thing wrong so Im just curious

this is a crankcase breather ,,,,that as you can see lets the air pass between the motor and the plenum (intake manifold )

on the k100  if air gets into this section via other means than the afm (airflow meter ) in the top of the air box  the bike will run lean ...as there is no way to measure the air passing in

symptoms could be, that the bike idles poorly etc

if it is just a crack in the outer rubber and not yet sucking air, all should be ok ...but get a spare whilst you can  they aren't dear from motobins or motoworks

you can simulate the leak affect by undoing the oil filler on the right hand side with bike running .

hope that helps a little

it is just a bit dirty on the outside of the crack so I don't think its bad. I think it may be the cause of the small bit of hesitation I feel in low rpms and low gears. I've already ordered a new one from Beemer boneyard. i was just wondering what it did because I thought it just flowed air but I didn't understand how it got grimy only in that spot

a bit dirty on the outside ?

its sucking air .


and letting oil out when vacume is gone

this region pulsates with crank pressures and inlet vacume
primarily designed for several reasons ...keep negative pressure in the crankcase  and exhaust vapours accumulated through blowby etc back through the ignition process of ignition to burn the vapours off

Interesting. I noticed on the weekend that mine has developed a slight Hum/resonation at lower rpm ( around2500 ) so went looking and discovered my crank case breather hose was cracked at both ends with oil residue as described above. Also has perished rubber vacuum caps so I'll be ordering both items tomorrow. While I'm at it is there any other rubber bits I should be looking at/checking.


  Cheers
  Andrew


  P.S. where do you Aussie guys get your parts from. I'm guessing Munich would be the quickest.

yeah munich is a good and reliable supplier , if its in stock

the "champion rack" at supercheap  will get you  plastic vacuum cap - stoppers , . but for long term service something else is more preferable  

good luck

I did spot a pic on here somewhere of someone using thick-wall silicon tubing to substitute for the crankcase breather. As the OEM is £12-odd (AU$25+ ?) and (IMNSHO) poorly made, then I'd think it would be a cheap replacement in both cost and longevity. That's certainly the route I'm going the next time mine cracks.

I'm on my second breather hose in twenty five years 160,000 K's and the original is still usable as a spare. Still on the original accelerator cable, clutch cable and fast idle cable, must be something in the air.
Regards Martin.

If you do a bit of your own work on infernal combustion engines, it can be worthwhile buying a kit of vacuum caps - eBay a good starting point - not expensive. I prefer silicone or rubber ones rather than plastic as they cope with heat better over time. If you have a kit with correct sizes available (or loose spares on hand) you are more likely to replace dodgy ones when they first show signs of ill-health.

MartinW wrote:I'm on my second breather hose in twenty five years 160,000 K's and the original is still usable as a spare. Still on the original accelerator cable, clutch cable and fast idle cable, must be something in the air.
Regards Martin.

160,000K is eight years commuting for me - you can add X amount of miles for pleasure on top of that. LFB lives outside in all weathers; consequently the crankcase hose (and vacuum caps) only tend to last about four years.

charlie99 wrote:yeah munich is a good and reliable supplier , if its in stock

the "champion rack" at supercheap  will get you  plastic vacuum cap - stoppers , . but for long term service something else is more preferable  

good luck

  Cheers Charlie. Munich has vacuum caps at only $2 each so I'll pick some up with my breather hose.

redrockmania wrote:If you do a bit of your own work on infernal combustion engines, it can be worthwhile buying a kit of vacuum caps - eBay a good starting point - not expensive. I prefer silicone or rubber ones rather than plastic as they cope with heat better over time. If you have a kit with correct sizes available (or loose spares on hand) you are more likely to replace dodgy ones when they first show signs of ill-health.

  Cheers mate

Dai wrote:I did spot a pic on here somewhere of someone using thick-wall silicon tubing to substitute for the crankcase breather. As the OEM is £12-odd (AU$25+ ?) and (IMNSHO) poorly made, then I'd think it would be a cheap replacement in both cost and longevity. That's certainly the route I'm going the next time mine cracks.

Next time yours crack. Just the thing and cheap too  

https://coffeeenemas.com.au/shop/parts/silicone-enema-replacement-tube/?gclid=CjwKCAiAr_TQBRB5EiwAC_QCqw1dNmj1oIMYtHv1z5c4lAgBNVqItlSnHofhAdS8QZxtEFB-sLwTrBoC0fIQAvD_BwE

Hmmm I suppose they would work but I wouldn't want a used one

RicK G wrote:Hmmm I suppose they would work but I wouldn't want a used one

   . It could get you out of a tight situation though

I got my new crank case pipe and some vacuum rubbers yesterday and popped them in this afternoon. The old ones were looking a wee bit sad .

  The other end was much the same.







  Started her up and noticed a better idle straight away. I'll take her for a run tomorrow if the rain stops......yes it does rain here in Oz occasionally .