Author Topic: Air Accumulator (a.k.a. "The Cup")  (Read 7366 times)

Offline frankenduck

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Air Accumulator (a.k.a. "The Cup")
« on: September 08, 2011, 12:13:05 PM »
All K bike gas tanks have two vent pipes protruding from underneath the right rear of the tank.  Oftentimes these are connected to two hoses.  The forward hose, from the factory, went to a vent on the top of the engine block above the middle of the timing cover.  (Rumor has it that this was so that gas/fumes would vent back into the engine to meet California emissions requirements.)  The rear hose was an overflow hose that drained to the pavement behind/under the right side peg plate.

Many times the vent on the front of the engine has been capped and the hosed plugged since it really doesn't do much.

These hoses can be a pain to keep connected and also keep them unkinked when re-installing the gas tank.  An alternative is to install "The Cup"  (Part number 16132307467 and called an "Air Accumulator" in the BMW parts catalog - cost is about $3) under those two vent pipes.  Then attach a hose to the pipe at the base of the cup to drain behind/under the right side peg plate.

Here's what  the cup looks like in the parts diagram for the gas tank:

Here's what one looks like when installed:

The upside of doing this is that it makes tank removal and installation much easier and you don't have to worry about those vent hoses getting kinked.  The downside of doing this is that you'll occasionally get a whiff of gas when you're riding.  Big deal.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline billday

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Re: Air Accumulator (a.k.a. "The Cup")
« Reply #1 on: September 09, 2011, 09:18:48 AM »
I like a whiff of gas. Installing this device would save me the bother of unlocking my gas cap and sticking my nose in there.
  • New York State, USA 10977
  • 1985 K100

Offline johnny

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Re: Air Accumulator (a.k.a. "The Cup")
« Reply #2 on: October 31, 2015, 09:50:40 AM »
have been sitting in the motobrick garage with no corn ethyl and two bottles of chevron techron in the tank... after trying the cup sniff and the cap sniff methods for the past few hours... i conclude that full bodied sniff from the cap has the best results...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline woodgeek

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Re: Air Accumulator (a.k.a. "The Cup")
« Reply #3 on: February 02, 2018, 02:44:27 PM »
So, is the Sigg bottle on this K100 a custom version of "the cup"?











  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Air Accumulator (a.k.a. "The Cup")
« Reply #4 on: February 02, 2018, 02:48:44 PM »
So, is the Sigg bottle on this K100 a custom version of "the cup"?
No. It is a stylish coolant reservoir or hootch flask.
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Offline woodgeek

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Re: Air Accumulator (a.k.a. "The Cup")
« Reply #5 on: February 02, 2018, 02:49:24 PM »
Thanks for that.  :2thumbup:
  • Henderson, NV
  • 1985 K100RT

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