Author Topic: Filler cap vent assembly  (Read 6741 times)

Offline woodgeek

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Filler cap vent assembly
« on: March 07, 2018, 12:54:51 PM »
Does anyone have an exploded diagram or pictures for our gas cap vent assembly? I've got the gasket kit for the rebuild and I've watched Chris Harris' video but I need more help than that. When I took my gas cap apart to get the lock out, some black plastic pieces popped out and don't seem to want go back together in the way that I envision them fitting together. They don't look broken and I don't see any signs of previous adhesive. Tonight I can take some pics of the parts. I was researching online and thought I'd pick the brains of the experts.
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #1 on: March 07, 2018, 01:13:04 PM »
This might supplement Chris Harris's video. We'll all know more when you post clear photos of the parts. There aren't many to handle.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
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Offline woodgeek

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Re: Filler cap vent assembly
« Reply #2 on: March 07, 2018, 01:15:57 PM »
We'll all know more when you post clear photos of the parts. There aren't many to handle.
Thanks Laitch. That document helps a lot. I'm going to run it through google translate. My parts in question are the dicktgummi and the part with the four holes.  :yow

Do my pics have to be oriented properly? I love me some sideways images. :eek: :hehehe
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #3 on: March 07, 2018, 01:19:20 PM »
I love me some sideways images. :eek: :hehehe
A tragic waste of love. :nono
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
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Offline Laitch

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Re: Filler cap vent assembly
« Reply #4 on: March 07, 2018, 01:55:50 PM »
That document helps a lot. I'm going to run it through google translate. My parts in question are the dicktgummi and the part with the four holes.  :yow
When I took my gas cap apart to get the lock out, some black plastic pieces popped out
Starting at 1:21 in Harris's video, it seems clear that there are only two parts—a vent cup and a flange/spacer.—comprising parts with those two names.

Awaiting your grand reveal.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline woodgeek

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Filler cap vent assembly
« Reply #5 on: March 07, 2018, 01:59:57 PM »
Looking at that PDF, it appears that the pieces I have questions about are partially held in place by the sliding latch plate. But, I’ll know for sure when I have parts in hand tonight.

Thanks for the German supplement—uber awesome. I printed it out and put it in Chapter 16 of the mothership manual.
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #6 on: March 07, 2018, 02:17:07 PM »
Looking at that PDF, it appears that the pieces I have questions about are partially held in place by the sliding latch plate.
Harris's video makes it plain that those two pieces are latched by rotation into the assembly beneath. You sure you aren't watching a Rammstein video instead of Harris's?

Your comments are making your reveal compelling viewing. Thanks!
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline woodgeek

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Re: Filler cap vent assembly
« Reply #7 on: March 07, 2018, 02:35:25 PM »
Harris's video makes it plain that those two pieces are latched by rotation into the assembly beneath. You sure you aren't watching a Rammstein video instead of Harris's?

Your comments are making your reveal compelling viewing. Thanks!
Watching Harris' video again, along with your comments and the PDF visuals makes me think that I was indeed watching a Rammstein video before or I was high from brake cleaner fumes when I tried to piece together these parts. I was trying to piece together parts that don't mate. Specifically, the eccentric part that operates the latch and the four holed vent cap that Chris removed with pliers in the video. 
  • Henderson, NV
  • 1985 K100RT

Offline woodgeek

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Filler cap vent assembly
« Reply #8 on: March 07, 2018, 11:02:01 PM »
So, here are the pieces that I have.






I think these parts are supposed to be one piece.


  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #9 on: March 08, 2018, 11:12:33 AM »
I think these parts are supposed to be one piece.

What did you do with the spacer as indicated by the red arrow in the attached photo?
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
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Offline woodgeek

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Re: Filler cap vent assembly
« Reply #10 on: March 08, 2018, 11:20:16 AM »
The rubber spacer is there. It's in the first photograph. I'm not sure how I'm going to reattach the broken piece. It needs to be able to endure some pressure and rotational stress from the lock cylinder.
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #11 on: March 08, 2018, 11:28:21 AM »
The rubber spacer is there. It's in the first photograph. I'm not sure how I'm going to reattach the broken piece. It needs to be able to endure some pressure and rotational stress from the lock cylinder.
Where is "there?" I can't see it in its correct position in the photo of your assembly. I'm referring to part #4 of your assembly.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline woodgeek

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Re: Filler cap vent assembly
« Reply #12 on: March 08, 2018, 11:29:53 AM »
Where is "there?" I can't see it in its correct position in the photo of your assembly. I'm referring to part #4 of your assembly.
Sorry. It's in the image below.
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #13 on: March 08, 2018, 12:07:28 PM »


I think these parts are supposed to be one piece.

It's all clear to me now.

Was it broken by incorrect rotation direction during removal of part #2? I think repair might be a result of trial-and-error success after applying epoxy, letting it fully cure then testing for strength by installing it and then removing it a couple of times in the cap assembly. There isn't much bonding surface though.

Search for a donor fuel cap assembly might be considered.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline woodgeek

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Re: Filler cap vent assembly
« Reply #14 on: March 08, 2018, 12:20:33 PM »
It's all clear to me now.

Was it broken by incorrect rotation direction during removal of part #2? I think repair might be a result of trial-and-error success after applying epoxy, letting it fully cure then testing for strength by installing it and then removing it a couple of times in the cap assembly. There isn't much bonding surface though.

Search for a donor fuel cap assembly might be considered.
Thanks for your thoughts Laitch. I was having similar thoughts about the epoxy. There's not much surface area there. I'll keep an eye out for a donor cap. Do you know if any other BMW filler caps fit this tank? Every cross reference I've checked only lists K75,K100,K1100 and K1.
  • Henderson, NV
  • 1985 K100RT

Offline Laitch

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Re: Filler cap vent assembly
« Reply #15 on: March 08, 2018, 12:35:09 PM »
Do you know if any other BMW filler caps fit this tank? Every cross reference I've checked only lists K75,K100,K1100 and K1.
I don't know, but there should be enough out there of what does fit to get you going. There are aftermarket offerings too. You'll see some in the Custom section and could PM the builders if no links are supplied in the text.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline woodgeek

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Filler cap vent assembly
« Reply #16 on: March 09, 2018, 11:49:29 AM »
So I began the repair last night. I cleaned both parts with alcohol and used a file to put a chamfer around the circumference of both parts, similar to what you do in welding. This served three purposes. It exposed fresh surfaces for better adhesion, provided a rough surface for better adhesion and made room for more JB Weld to strengthen the joint.

I used the regular, slow curing JB Weld because from all the research I’ve seen, the quick curing epoxy products don’t have strong surface adhesion of their slow curing counterparts. There are a lot of videos on YouTube that illustrate this problem. The manufacturers list the strength of their epoxies but no one talks about the adhesion problems of quick cure epoxies.

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  • 1985 K100RT

Offline The Mighty Gryphon

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Re: Filler cap vent assembly
« Reply #17 on: March 09, 2018, 12:37:00 PM »
Quick cure epoxies don't have the molecular bonds of the slower setting versions.  Hence they form slightly weaker bonds that are more suseptible to degradation by UV and organic solvents.  It's always wise to use the slower curing versions.
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Offline woodgeek

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Re: Filler cap vent assembly
« Reply #18 on: March 09, 2018, 12:39:56 PM »
Quick cure epoxies don't have the molecular bonds of the slower setting versions.  Hence they form slightly weaker bonds that are more suseptible to degradation by UV and organic solvents.  It's always wise to use the slower curing versions.
Thanks for that. Nice to have some scientific theory to go along with what I’ve seen in the YouTube videos.
  • Henderson, NV
  • 1985 K100RT

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