R25/2 Gas Tank Outlet

Begonnen von Kurt in S.A., 14 August 2022, 23:50:13

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Kurt in S.A.

I was out today on the bike.  Nearly within sight of my house, the bike just died.  I have an external filter for gas and I could see that it was empty.  I wasn't that close to needing fuel and could see gas moving around in the tank when I opened the cap.  I flipped the petcock to reserve but still no gas.  I sloshed the bike back and forth to see if there was some debris on the outlet but that didn't help.  I only had to push the bike 50 meters or so to get to the top of the hill and I was able to coast all the way home!!

I did some looking inside the tank and used a flashlight to look down at the outlet which is on the rider's right rear of the tank.  I appears that there is something covering up the outlet.  I'll confess that I have had a "minor" rust issue with the tank and what was covering the outlet looked like a layer of rust flakes.  I know, I know!  I've needed to deal with the rust in the tank for some time...maybe my time has come!!

I was able to get a coat hanger and scrape away at the outlet and eventually gas flowed out and filled up the external filter, so I know that's the problem.

Years ago when I first got the bike, I attempted to remove the external coupling to the tank outlet but it wouldn't budge.  I didn't want to twist off the tank bung threads, so I left things alone.  Something else to deal with.

Anyway, I wondered if anyone had pictures of what this inside the tank outlet looks like.  Is it something that sticks up inside the tank from the petcock?  If I could get the coupling off, I would probably see.  I suspect that this petcock and external coupling is original to the bike.

Thanks for any insight!

Kurt
Kurt in S.A.

Kurt in S.A.


Kurt in S.A.

Taz

Hello Kurt.

Those couplings are basically a nut with threads running opposite directions both each ends...afaik the tank would have a standard thread, the petcock a "left" thread...that way both parts keep their orientation when tightening the nut and still the gasket ring receives sufficent pressure to be tight.

Hope this helps, Ute
Ich hab noch nie einen Sarkasmus vorgetäuscht


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Taz

Regarding how that looks like inside the tank...you would expect to stick out two tubes of different length from the petcock...the longer one being the normal "open", once the fuel level drops below a certain level you'd switch to reserve and then a much shorter tube belonging to that position would allow to drain the fuel tank to basically really empty...
Ich hab noch nie einen Sarkasmus vorgetäuscht


auf Tour:

Zipfelreise (2019)
Cymru "Radnor Revivals" (2016)
Alba "Isle of Skye" (2013)
Austria Großglocknerhochalpenstrasse (2012)
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Kurt in S.A.

#3
I don't see any tubes sticking up...that what's I was wondering about.  Here's what I see.TankOutlet.jpg 

I wonder if it's something like shown in this parts diagram?

https://www.bmwclassicmotorcycles.com/parts/all-parts/fuel-tank-r24-r252/

Kurt
Kurt in S.A.

mekgyver

#4
Hi Kurt, i think this is the dome inside that contains the thread for the bolt from outside :
x    07119914032    Hex bolt, rear tank mounting    R25/2, M8x1x25    2

Please notice carefully and verify those informations : it could be the correct thread is M8x1mm, i`m nearly shure.
Greetings, mek
... 73er-Gang

Taz

Hello Kurt.

I would think mek is correct regarding the "dome", that's just part of the mounting system (insert nuts, to be more precise, see https://www.bmw-einzylinder.de/Vergleichstabelle/default.html#hahn_EN ).

Problem is, the tank that page of yours is showing appears to be a R24 tank, where the fuel tap is connected via inside thread of the tank (open insert nut, for obvious reasons), but claiming the tank to be R24-R25/2...which would present some nice problems if you'd try to put that on your bike.

Maybe you can provide a picture of the fuel tap from the side (outside!), that would allow to help you with taking it out...after that the next step would be identifying and fixing/completing, if necessary.

All the best, Ute

PS: That bolts used for the rear end of the tank are indeed meant to be M8x1, although on a worrying number of motorcycles you will find standard M8 in there...easier to come by....
Ich hab noch nie einen Sarkasmus vorgetäuscht


auf Tour:

Zipfelreise (2019)
Cymru "Radnor Revivals" (2016)
Alba "Isle of Skye" (2013)
Austria Großglocknerhochalpenstrasse (2012)
Alba "Spittal of Glenshee" (2011)

Kurt in S.A.

You guys helped me with the rebuild of my Everbest petcock a while ago.  Here's the thread...pictures of the outside tank attachment can be seen there.

https://bmw-einzylinder.de/forum/index.php?topic=18077.0

Kurt
Kurt in S.A.

4Taktix

OK, then you can loosen the sleeve-nut clockwise, seen from above.
You can use some good penetrating oil before and - important - a wrench with a tight fit !
The thicker the jaws, the better. Also heat will help softening the gummy remains of gas.
Don't use worn out bargain wrenches from the rummage table.

Regards,
Sascha

Think outside the box !

Kurt in S.A.

Thanks, Sascha.  That has been my plan.  I hope to find out more about what's inside the tank.

Kurt
Kurt in S.A.

cwf

What you see inside the tank, is that a fine mesh brass filter (clogged)? My /6 and /2 petcocks have a filter over the two tubes (so no external filter necessary).

Charlie.

Kurt in S.A.

Charlie -

I think that is the case.  The white area you see on the right side as you look at the picture is where I used the coat hanger to scrape up/down which I think got rid of some of the flakiness.  Doing that allowed the fuel to flow out and I could see that in the external filter.

Kurt
Kurt in S.A.

Borgward

Kurt, the brass filter inside the tank would look different. What you see is certainly the fixation dome as mentioned by Mek in #4

Hubi

Kurt in S.A.

Hmmm...now that is making some sense.  What I was looking at was not the gas outlet.  :)   Once I get the tank off, I might see if I can round up some kind of remote camera to get a better sense of what's going on.

Kurt
Kurt in S.A.

4Taktix

Maybe your girl has a small makeup-mirror, so you could at least have a peek.
However, you could try and blow backwards through the petcock to free the mesh from flakes and let them
'swim free'.
Then lay the tank on it's side with only say quarter gallon or less fuel in it, swing it back and forth
and try to catch most of the flakes through the filler with a coarse rag or cotton-ball on a stick or similar.
repeat as needed.
Should be cleaned thoroughly, to prevent remaining flakes or dirt from clogging the mesh/petcock partially.
This would lead to lean mixture, without noticeable decrease in speed, until the piston jamms, due to
overheat.

Regards,
Sascha

 
Think outside the box !

Kurt in S.A.

No girl here to check with! :(  But I have a small dental mirror so I went looking again.  And I can barely see past that dome in the base for the tank support bolt to finally see at least one straw sticking up in the very rear of the tank.  Hard to manipulate the mirror, flashlight, and eyeball to see anything.  So, I guess I have the "main" tank straw and likely the "reserve" straw is no longer in place.  Hard to tell.

The previous owner of the bike had the fenders and tank repainted to a faithful German police green.  When I first looked in the tank way back when, I could see the bare steel, so the previous owner must have really stripped the tank to do the repaint.  Again, my bad as I should have immediately realized no coating and took care of it then.  But as I said, I couldn't get the petcock/coupler off so I just "kicked the can down the road"!!

Kurt
Kurt in S.A.

Kurt in S.A.

It's been a while and haven't done much...waiting for the weather to be better!  Got the tank drained and have begun to soak the nut that connects the petcock to the tank outlet stub.  If I remember correctly, this nut (19mm it seems) draws the petcock and the tank together.  One side has reversed threads while the other side is regular threads.

I don't want to tighten when I should be loosening.  If I have my wrench (spanner) on the 19mm nut, which way do I turn it to try and loosen things?  If I were to look down from above, does the wrench go clockwise or counter clockwise?

Thanks...Kurt
Kurt in S.A.

Kees

Clockwise. It's like you turn a normal screw into or out of the tank.

Eppo

Hy Kurt,
pictures saying more than thousand words.
This is my R25/2 tank lying upside down on my workbench.

Tankverschraubung_20221010_065450_bearb.jpg

Tankverschraubung_202210_070134_bearb.jpg 
Geht nicht, gibt's nicht. Einfach kann ja jeder 😁.

Borgward

and don't forget to counter (hold) the petcock

Hubi

Kurt in S.A.

Thanks.  I've been soaking the threads with a penetrant for a few days.  It doesn't want to move.  I'll continue to soak, but if I can't loosen the nut, I'll have the Dremel if off.

Kurt
Kurt in S.A.

Borgward

#20
Kurt,
as you cannot loosen the screw connection between the tank and the nut you may try to loosen the connection between the petcock and the nut:
grab the petcock instead of the nut with another spanner and turn it counterclockwise (as if you would screw it into the tank).  (counterclockwise when  looking down from above)

Hubi

Kurt in S.A.

Finally...lots of penetrant, time, heat from a hair dryer, slight tapping on the end of a spanner...the nut to the tank finally let loose.  Whew!  I thought there would have been a filter inside the tank around the intake straws but there was nothing.  Not sure if the rust flakes show up in my pictures.  I don't see how this small amount would have blocked the intake of gas and stopped the engine.  At any rate, now I'll move the next step of removing the rust inside the tank and getting it coated.  I have some research to do.

Kurt
Kurt in S.A.

Heiko

Hi,

I think the filter is getting lost over the years.
Ariel motorcycles... upon which the sun never sets.

Kurt in S.A.

#23
I managed to finally separate the nut from the top of the petcock.  I was expected to see something that I could remove in terms of the straws.  But they seem to be soldered in or part of the top of the petcock.  Is that what they are supposed to look like?

I took a closer look at the coupling nut.  I see the remnants of a red washer which is there to seal between the two surfaces.  Plus I also see the remains of the filter screen/wire/mesh.  So that does answer the riddle of why no internal filter.

Also, I'm not seeing the separate filter for sale.  I see on BMW Salis they are selling the whole petcock assembly for around 50 Euros.  Maybe it's best to just but the whole thing ready to install??

Kurt
Kurt in S.A.

Taz

Hello Kurt.

Regarding the "straws"...afaik those would just be brass tubes, press-fitted in the petcock's body...but after 70-odd years things tend to look a bit strange...

Rabenbauer offers this filter: 16 12 4 084 008.E Filter für Benzinhahn "Frankf. Modell" (Zulauf) R25/3 - R69S, but without image it's difficult to decide whether that might be a solution..

Kind regards, Ute
Ich hab noch nie einen Sarkasmus vorgetäuscht


auf Tour:

Zipfelreise (2019)
Cymru "Radnor Revivals" (2016)
Alba "Isle of Skye" (2013)
Austria Großglocknerhochalpenstrasse (2012)
Alba "Spittal of Glenshee" (2011)

Kurt in S.A.

Thanks, Taz.  I notice that it mentions "R25/3 - R69S".  Might not be right for a R25/2.  The R25/2 is an M16x1 threads whereas I think the part you mention is M20x1.  So likely wouldn't fit.

Kurt
Kurt in S.A.

Taz

You're right regarding the thread size ( https://www.bmw-einzylinder.de/Vergleichstabelle/default.html#hahn_EN:kopfhau:
Sorry for mentioning it...
Ich hab noch nie einen Sarkasmus vorgetäuscht


auf Tour:

Zipfelreise (2019)
Cymru "Radnor Revivals" (2016)
Alba "Isle of Skye" (2013)
Austria Großglocknerhochalpenstrasse (2012)
Alba "Spittal of Glenshee" (2011)

Kurt in S.A.

No problem!  At least you're helping me think about things!!

Kurt
Kurt in S.A.

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