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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: superwesman on May 24, 2018, 02:01:42 PM

Title: what's the preferred method to "cap" the crankcase when bypassing fuel overflow
Post by: superwesman on May 24, 2018, 02:01:42 PM
On my 90 K75s, some PO had used a zip-tie to choke off the line that would have fed fuel overflow from the tank back to the crankcase.


Is this a reasonable method for capping this?  I worry that this is allowing an air leak from not being choked off sufficiently.  I also worry that this hose itself will deteriorate and need to be replaced, only to be tied off again. 


what's the preferred method for "pluggin' yer crankcase hole" as they say ?
Title: Re: what's the preferred method to "cap" the crankcase when bypassing fuel overflow
Post by: johnny on May 24, 2018, 02:25:40 PM
greetings...

i roll up a foam earplug and slide it in there and hold it till it expands and seals..

j o
Title: Re: what's the preferred method to "cap" the crankcase when bypassing fuel overflow
Post by: Scott_ on May 24, 2018, 04:19:24 PM
The proper way is to get a rubber cap for the nipple that the other end of the hose connects onto. You can find them at an auto part store in the "help" accessory isle.
One thing to remember is that the caps will also be rubber and only will last so many years and still have to be replaced like anything else rubber on the bike.
Title: Re: what's the preferred method to "cap" the crankcase when bypassing fuel overflow
Post by: Laitch on May 24, 2018, 04:35:45 PM
On my 90 K75s, some PO had used a zip-tie to choke off the line that would have fed fuel overflow from the tank back to the crankcase . . .
It was designed for fuel vapor transfer—not to feed excess tank fuel into the crankcase to dilute the oil.  :giggles   The vapor would then wend its way through the crankcase, into the z-tube—or the more complicated 16V system—back into the intake manifold, eventually be consumed by combustion, and the whole system would preserve the Great State of California and perhaps other less important locales. As it turns out, few people cared what happen there or elsewhere and it was another annoying part that could fail so it was discontinued. Thus the evolution of cap-the-nipple, earplugs, earwax, miniature carved totems and other plugging strategies.
Title: Re: what's the preferred method to "cap" the crankcase when bypassing fuel overflow
Post by: stokester on May 24, 2018, 05:01:15 PM
It was designed for fuel vapor transfer—not to feed excess tank fuel into the crankcase to dilute the oil.  :giggles   The vapor would then wend its way through the crankcase, into the z-tube—or the more complicated 16V system—back into the intake manifold, eventually be consumed by combustion, and the whole system would preserve the Great State of California and perhaps other less important locales. As it turns out, few people cared what happen there or elsewhere and it was another annoying part that could fail so it was discontinued. Thus the evolution of cap-the-nipple, earplugs, earwax, miniature carved totems and other plugging strategies.
I found a vent on my Airhead with the pulse-air system removed plugged in a similar way.  As Laitch stated plugging it with whatever is available is sufficient and yours is probably like many others.