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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Wheezyryder on October 10, 2020, 09:23:05 PM
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I recently bought a 1985 K100 (produced in July, 1984 according to the VIN) with about 45k miles on it. It's been sitting unused in a garage for the last few years so I'm in the process of getting it roadworthy again. So far new battery, tires, final drive spline lube, rebuilt front master cylinder, new spark plugs and drained/cleaned the fuel tank.
Before I drained the tank I noticed it leaking fuel for the fuel sender unit at the front left side of the tank. Did a bit of searching on this site and found out that this style of sender unit is only on the early model K100s. According to my research, of the fuel seemed to be leaking between the sending unit and the retaining nut and not through the wire penetrations of the sending unit itself, then the likely culprit was the rubber gasket. Mine does not seem to leak through the wire penetrations so I ordered the gasket from Max BMW.
I installed the new gasket, sending unit and retaining nut and it still leaks. Has anyone had the same problem? I disassembled and reinstalled it a couple of times to make sure that the gasket wasn't pinched or out of place, and it didn't seem to be.
A couple of questions:
1) There's an arrow on the sending unit (see first pic). Is there a certain direction that the arrow should point in order to get it to seal? I tried a few different orientations and still got the leak.
2) The flange on the sending unit doesn't seat evenly against the retaining nut (see second pic). The gap between them is larger in some places than others. Should it be like that?
I have the Haynes manual and I downloaded the BMW service manual and they both show procedures for the newer, square sending unit and not the style I have. Djoes anyone have an idea what I'm missing?
I'm really itching to get this leak fixed because I haven't actually been able to ride the bike yet and this is the last thing keeping me from trying it out.
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Uneven spacing
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Sending unit location/style
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Does the O-ring have a flat surface or a curved surface? What is the part number on the package?
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Laitch- the O ring had a flat surface. I've thrown out the package but based on my confirmation email the part number I ordered was 61311459448. It did appear to be the same O ring and the old one that I removed.
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With the uneven spacing you pointed out, something sure doesn't look right, like the sender is either crooked in the hole(which I doubt) or the nut is cross threaded.
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Scott- I thought it didn't look right as well. I have checked and double checked that the retaining nut is not cross-threaded. It didn't feel cross-threaded as I screwed it on, and I don't see any damage to the threads of the retaining nut. I would think that if the plastic nut were cross-threaded onto the aluminum threads, there'd be visible damage. Which leads me to wonder if the sending unit itself is damaged, or if it is supposed to have uneven spacing? The far end of the sending unit is very close to the inside wall of the fuel tank when it is in place, so I thought there's a possibility that it is supposed to be canted toward the center to avoid touching. I wish I could see one of these in place on another bike so I could determine if this is normal or not. I REALLY hope the sending unit isn't damaged, as the part is no longer available from BMW and a quick search of the interwebs did not show a single used one for sale (searched Google, eBay, Beemer Boneyard).
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A bit more searching shows that there may some used ones available internationally, but I sure do hope not to have to go down that rabbit hole. Sounds expensive, slow and painful.
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What is that red substance at the base of the nut? Is is the same as what's on the seam of the tank?
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Laitch-The tank (and the whole bike) were originally a wine red color. It's been painted black at some point. Actually looks like a fairly well done paint job but has since got some minor damage and chips. The red you see is the original paint. The threads on the tank appear to be in good condition and clean, without any sealers out other substances on them.
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Remove the sender. Post a few photos of the tank hole, the reverse side of the flange with the "arrow" and the sender itself. I haven't worked with this sender but if the parts haven't been damaged then there might be an alignment tab you're overlooking.
Maybe somebody with one of these old tanks will chime in. This shouldn't be complicated.
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Laitch- I'll get some pics and part them as soon as I get to the house.
I agree that this is probably something simple I'm overlooking. With as many of these bikes as there are on the road, I can't be the first to have this issue. Hopefully someone can chime in with the solution.
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With as many of these bikes as there are on the road, I can't be the first to have this issue.
Somebody had to be first. Why wouldn't it be you? :laughing4-giggles: You're breaking new ground here. icon_cheers This style of fuel sender was only used for two years out of a run of maybe 7 years for 2V motos. I couldn't find another example of this problem's needing Internet consultation but I'm still looking.
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Laitch- I was hoping not to be the first guy to pioneer a new problem. Oh well 177381
Here are some pics
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Sending unit arrow
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tank hole
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More tank hole
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Is the twisted thing at the arrowhead a gasket?
(http://www.motobrick.com/gallery/3/1601-111020150941.jpeg)
Is this arrow pointing at a gasket?
(http://www.motobrick.com/gallery/3/1601-111020151045.jpeg)[
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In the top pic that's just a part of the tank. The bottom pic is pointing toward the new o ring.
I've been thinking about this. The inner part of that o ring seals between the cylindrical body of the sending unit. The outer part of the o ring seals against the threads of retaining nut (which seems like a bad idea). My suspicion is that the fuel is leaking at the threads. I went on the webs and found some PTFE thread sealant tape that's fuel resistant. I'm thinking I may order that and try some. If it doesn't work I can just remove it.
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[size=78%]The gasket should be contacting the upper inside surface of the nut, the sides of the sender body and the opening of the threaded port. If this were my problem I'd clean the corrosion from the inside of the hole and the tank port threads with a Scotchbrite pad, wipe clean the sender body, use a [/size][size=78%]scant[/size][size=78%] coating of petroleum jelly on the sender body and gasket, shove the sender down into the passage then screw down the nut. You could orient what you're calling "the arrow" so it points toward the center of the tank as long as doing that doesn't necessitate twisting the electrical plug's wires severely to insert it.[/size]
Teflon paste or other sealing concoctions could come later if that doesn't work.
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Check the underside of the tank for a corresponding mark that you might have to align the arrow to.
Regards Martin.
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What is the condition of the flange on the sending unit that the gasket seals against? Any cracks in it or missing chunks?
Per Laitch's advice, clean the top of the threaded spigot on the tank and make sure there aren't any pits or dings in the sealing surface.
I wonder if a good cleaning of the sealing surfaces followed by a little silicone sealer before assembly would do the trick.
Finally, is it possible that the leak is along the wires?
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Remove the filler cap assembly for a look see. Is there a pipe or something pushing the sender unit off centre?
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Laitch- I did everything you said, except that I used WD40 to lube the o-ring before I put it in. I used a scotch brite pad on the inside of the hole in the tank and a Dremel with a brass brush to clean the threads. There's still a bit of discoloration but nothing that you can feel. Feels completely smooth/clean when you run your fingertip along it. Unfortunately, still leaking.
Martin- I looked for a mark or indentation on the tank that would indicate where the arrow should point. I don't see anything. I don't know if a mark was covered up or removed when it was repainted.
Mighty Gryphon- I inspected the sending unit, retaining nut and flange very closely with a light, and don't' see any cracks, holes or chunks missing. I also checked the sealing surface on the on the threaded spigot and I don't see any imperfections.
Daveson- Good thought. I removed the filler cap. The top of the sending unit is within a 1/4 inch of touching the wall of the fuel tank, but it doesn't touch. I spun it around 360 degrees and it doesn't touch anything no matter which orientation.
All- After acting on everyone's suggestions and disassembling/reassembling this thing several more times I still have the leak. I think I'm going to start trying some other things:
1)There's a good possibility that it's leaking through the threads of the retaining nut/spigot. I found a product on the web called Petro Tape. It's a PTFE/teflon thread sealing tape that's impervious to fuel. I can try that and if it doesn't work it won't hurt anything.
2) After putting together/taking apart so many times, the new O ring now has some imperfections. I'm gonna order a few more. I may also try doubling up the O ring. Nothing else I've tried worked and it can't hurt.
3) I really suspect that my sending unit and/or retaining nut is damaged in some way that is causing them to seat together crooked. Being crooked may twist the O ring just enough to not seal. If none of the other methods works, I may try sealing the retaining nut/sending unit together. I found a couple of RTV sealants that are impervious to fuel (Permatex MotoSeal is one of them). Then I could screw the whole thing in as a single unit. The only disadvantage of that plan is that I'd have to disconnect the wires from the fuel pump any time I need to remove the sending unit. No big deal.
I have to work 12 hour shifts the next few days (I'm an ICU nurse in the COVID unit of an Atlanta hospital) so I won't be able to work on it for a bit. Plus I need to order some things and wait for them to come in, Thanks for everyone's help so far. If anyone has a better idea in the meantime please let me know.
Regards,
Mike
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Laitch- I did everything you said, except that I used WD40 to lube the o-ring before I put it in. I used a scotch brite pad on the inside of the hole in the tank and a Dremel with a brass brush to clean the threads. There's still a bit of discoloration but nothing that you can feel. Feels completely smooth/clean when you run your fingertip along it. Unfortunately, still leaking.
Where's it leaking—bottom of the nut, top of the nut, somewhere else? If you need more excitement than an ICU—where I spent 10 luxurious days this April listen to the revelry at afternoon report—you might try tightening that nut a leeetle more.
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If the tank is vertical when you install the sender, gravity might cause it to be off centre before you tighten it.
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I may also try doubling up the O ring.
It's a gasket, not an O-ring. An O-ring has a round cross section.
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Laitch- it leaks between the retaining nut and the cylindrical body of the sending unit (where I'm pointing in the second picture and the beginning of this thread).
Sorry to hear you spent time in the ICU. I wouldn't wish it on my worst enemy. Especially now with all the policy changes and lack of staff/resources due to Covid.
I had been tightening it with a giant adjustable wrench. I finally went today and bought a 36mm socket to minimize the change of damaging the nut. When I get the new Oring in I'll try again, but it sure makes me nervous knowing it's unobtanium if I break it. Im cool as a cucumber when someone's heart stops at work, but torquing that plastic nut makes me sweat :laughing1:
Daveson- I think I was holding the sending unit perpendicular as I tightened, but I'll make sure to pay attention to it when I get a chance to work on it again. I would love for it to be something simple like that!
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The ICU was like being in a berth of a train's sleeping car passing through the perpetual twilight of a foreign country. It was interesting way to get out of town without leaving. I think I'd wish on my worst enemy the inability to make it to an ICU, at least the one where I was. Maybe I'll recommend yours to him. :laughing4-giggles:
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I wonder if you have a crack somewhere in the root of the threads on the tank spigot. It's possible that there is a crack someplace in the threads that the pull of the nut opens when torque is applied.
If the gasket is working properly between the flange on the sending unit and the end of the spigot there is no way fuel can get to the threads. With both of these surfaces clean and undamaged the gasket should have no trouble making a tight seal.
You will need a good magnifier to look at those threads.
Another possibility is that your new gasket is 30 years old and has hardened too much to make a good seal. You might want to let the gasket soak in some Automatic Transmission Fluid for a couple days while you are busy with other things. ATF has additives that will help soften rubber parts and might just help the gasket work.
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Another possibility is that the nut is bottoming against the tank before getting enough pressure on the gasket to give a good seal. In that case, adding a second gasket on top of the first one might fix the problem.
In the photos I think I counted eight threads on the nut above the gasket, and eight threads on the spigot. That doesn't seem to provide any additional room for tightening.
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In my last whack at this obsession, the attached photo shows the "arrow" pointing toward the rear fuel port to its right. I don't understand what the gasket surface of the nut bears against on the sender but I've seen this orientation a couple of times in my search. I've sent a query out to somebody familiar with this arcane part.
Buenas noches.
(http://www.motobrick.com/gallery/3/1601-121020001431.png)
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I'm thinking the gasket bears against the end of the threaded hole in the tank, on the photo in the post "tank hole" If the gasket is a bit damaged from the multiple attempts, I'd try spinning it around.
In the first photo the arrow is in line with a protrusion in the electrical socket, so it's a safe bet that a slot in the electrical plug lines up with the arrow before pressing the plug in.
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I'm thinking the gasket bears against the end of the threaded hole in the tank,
I'm with you on that one from the beginning of this confab. Your second observation is lost on me though. The only alignment I see is the "arrow" with an M on the nut. One of the problems with this thing is that it won't seat firmly on top of the mounting nut, and according to the owner, that's the place it's leaking. If the gasket were also bearing on the shoulder of the device that would help to seal the passage of fuel. The device doesn't appear to have been pressed in. What would be helpful is a photo like the one in Reply #13 showing if there is an alignment tab on the other bearing surface of the nut.
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I'm not familiar with the construction details of the sender unit, but does it have a moulded shoulder against which the gasket bears and then compresses between that shoulder and the tank when the nut is tightened? Or does tightening the nut cause the gasket to deform between the nut and tank which then seals by tightening around the circumference of the sender?
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I'm not familiar with the construction details of the sender unit . . .
Nobody yet seems familiar with its construction including the moto's owner, but there's hope on the horizon, as usual. :laughing4-giggles: If we knew how it was constructed the fun here would stall.
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I'm thinking the second one, so maybe a bit of Vaseline would prevent damage to the seal.
And I'm thinking, actually hoping, the sender is not at 90 degrees to the tank base, creating the uneven gap, and preventing the nut from fully tightening. One of the good things about bricks, you can get your hand in the tank, wiggle it straight maybe, while tightening.
In the centre of the nut, where the electrical plug goes, there are four pins. There is a thingy there in line with the outside of the plug and the arrow to prevent the plug from being installed in a wrong orientation.
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There is a thingy there . . .
The bump in the plug cavity and the arrow are parts of the same molding. The electrical plug connecting to the sender doesn't seem to be part of this problem, although anything seems possible under widespread contagion delirium. At least my hand sanitizer pump isn't leaking. icon_cheers
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That's it, the bump. So there will be a slot in the electrical plug that needs to line up with it. You can't see the bump when you put the plug there, so the arrow lines up with the slot. A bit like putting a trailer plug in (hopefully it's the same in the US of A.
Yep, I also think the arrow has nothing to do with the problem.
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"In the first photo the arrow is in line with a protrusion in the electri wecal socket, so it's a safe bet that a slot in the electrical plug lines up with the arrow before pressing the plug in."
Daveson- Aha! You're right about this! I was thinking that the arrow had some part to play in orienting the sending unit. But you're right... It lines up with the notch in the electrical connection that prevents plugging in the wires in the wrong orientation. I hadn't noticed that. It's likely just there as a visual reference when plugging in the wires. Therefore... The arrow likely has nothing to do with my leak or why the sending unit doesn't sit flush to the retaining nut.
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Daveson- Aha! You're right about this!
Hey! Aren't you supposed to be somewhere saving lives? You'd best get back to it and leave the futile deliberations to us.
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I guess an easy way to tell if there is a shoulder or not is to try and slide the nut off the sender body. If there is a shoulder, it will not be possible to remove the nut. If there is no shoulder, the nut should slide off. I'm guessing that there is no shoulder.
If there is no shoulder, all the sealing is banking on proper deformation of the gasket, which depends on properly shaped surfaces and a pliable gasket.
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Yep if all checks good, do the nut up finger tight, then put your hand in the tank and wiggle the sender straighter. Then you should be able to get it a bit more finger tight. Do it a few times till it's straight, then when it's straight, use a spanner. Hopefully that will do it.
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I guess an easy way to tell if there is a shoulder or not is to try and slide the nut off the sender body. Yep if all checks good, do the nut up finger tight, then put your hand in the tank and wiggle the sender straighter. Then you should be able to get it a bit more finger tight. Do it a few times till it's straight, then when it's straight, use a spanner.
It should be a snap for someone who has inserted a nasogastric tube. :laughing4-giggles:
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Laitch- they do occasionally give us breaks in between our life saving duties. And of course when I'm on break I'm thinking about the important things in life... Like why my motorbike won't stop leaking fuel?!? And yes I've done plenty of nasogastric tubes. If fact, if you can think of a hole in the human body, I've stuck a tube in it.
Rbm- it is not possible to remove the nut. I can get the sending unit to sit flush with the nut when it's not screwed in. But when I screw it into the tank it gets crooked.
I've tried reaching into the tank to steady the sending unit while I tighten the nut. Couldn't figure out why but it kept getting crooked. I'll try again tonight after work.
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In that case, the gasket is being sandwiched between the shoulder and the face of the tank opening. If the sending unit cants in the same way every time, then there is possibly some distortion in the metal in the opening that is causing the sending unit to hang up. Check the uniformity of the tank opening to make sure it is perfectly circular, and smooth. Is there any evidence on the plastic of scoring caused by metal shards? Another thing to try would be to remove the gasket and see if the sending unit can be inserted into the tank opening to the point where the shoulder will mate perfectly in the opening.
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Alright everyone...after thinking about this for the last couple days I went out today and looked at the problem again. And I realized that the sending unit stays perpendicular and flush to the retaining nut most of the way while screwing it down. It's only in the last 1/8 inch or so of the retaining nut's travel that the sending unit gets crooked. I'm still not sure why it get's crooked. When it gets crooked, the sending unit flange would no longer put even pressure to compress the gasket against the spigot on the tank. So I'm going to try using 2 gaskets to shim it out a bit in the hope that it would tighten down without getting crooked. Already ordered new gaskets.
Then I removed the sending unit/ retaining nut assembly and looked at the inside of it while making it crooked. I realized that even when it is crooked, it seems that the inside diameter of the gasket maintains a tight seal around the cylindrical shaft of the sending unit. But the outside diameter of the gasket pulls away from the threads of the retaining nut. So I thought that a thread sealer tape might help to fix any imperfections in that seal. I ordered a product called Petro Tape that is basically a fuel proof teflon tape. If the double gasket doesn't work, I'll give that a shot.
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Might there be a little rock or something like that which might come out with compressed air, both sides of the nut, after removing the seal?
So now I'm thinking there is a shoulder for the sender over the tank outlet like RBM asked way back, is that right?
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Daveson- I tried your suggestion and blew compressed air in from both sides. Didn't see anything come out and it still gets crooked when you screw it on the tank. And yes there is a shoulder or flange on the sending unit that sits over the tank outlet (I think I understand your question correctly). I'm gonna post some pics but it's difficult to get a good pic to show the inside.
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That first pic shows the whole sending unit/retaining nut assembly with the gasket pulled back over the cylindrical body of the unit. The next 2 show the retaining nut end of the assembly from both sides. The nut is captured by a flange on both sides. The gasket is compressed between the inner flange and the mouth of the tank outlet.
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outer
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The nut is captured by a flange on both sides
A flange on both sides of the sender's body? Please clarify. In my opinion there should be some captive arrangement of the nut to the sender body—a flange on the body that snaps them together or a firm friction fit.
I'd apply a thin coat of sealant to the clean mating surface of the sender flange that contacts the outer surface of the nut, run the nut up the sender until the nut mates with the sender's flange, install the gasket until it seats on the nut, firmly press the assembly into the port so the sender's shoulder fits into the port and the nut's threads are at the point of engagement, then tighten the nut with one hand while pressing the sender with the other.
When viewing photographs of a round or cylindrical part, it's helpful to have enough of them to evaluate the entire perimeter of the part.
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With the sender out of the tank is the nut square to the sender body when you press it down on the flange that bears against the outer edge of the spigot? ie. Is there something between the nut and the flange it is bearing against?
Did you run your finger around the inside of the spigot to feel if there are any imperfections that can hang up the sender?
Is the nut staying square to the spigot as it's being screwed down? ie.Are you absolutely sure it isn't cross threaded?
What you describe as the sender cocking as the nut gets to the end of it's travel makes me think the sender is either binding in the spigot or there is something between the nut and the flange that bears against the gasket. The only other possibility is that the bearing surface at the mouth of the spigot is not square with the bore of the spigot or the flange on the sender isn't square to the body of the sender.
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With the sender out of the tank is the nut square to the sender body when you press it down on the flange that bears against the outer edge of the spigot? ie. Is there something between the nut and the flange it is bearing against?
Did you run your finger around the inside of the spigot to feel if there are any imperfections that can hang up the sender?
Is the nut staying square to the spigot as it's being screwed down? ie.Are you absolutely sure it isn't cross threaded?
What you describe as the sender cocking as the nut gets to the end of it's travel makes me think the sender is either binding in the spigot or there is something between the nut and the flange that bears against the gasket. The only other possibility is that the bearing surface at the mouth of the spigot is not square with the bore of the spigot or the flange on the sender isn't square to the body of the sender.
This is what I was implying by asking my questions in post #41.
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It has been over a year since I have the sending unit out of Big Red and replaced that gasket, so I am a little fuzzy.
No issues at all that I recall. I put the gasket into the nut and made sure it was fully seated and the nut turned freely.
I assume Pic #2 shows the gasket removed and the room for the gasket between the stem and nut.
IIRC, I installed it with the tank upside down, so the hole was level and snugged it tight.
I do not see where you attempted to install the sending unit without the gasket to see how far it can be installed.
Interesting, Max fiche lists the part as a "Gasket Ring" and it is flat, but then they further describe it as an "O-Ring"
06 61 31 1 459 448 GASKET RING 1 $1.45ADD TO CART
Part Thumbnail Part Thumbnail
Part Thumbnail
O-Ring, K75 - K1100RS.
I can not find any application for a K75 or K1100RS, only K100
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Interesting, Max fiche lists the part as a "Gasket Ring" and it is flat, but then they further describe it as an "O-Ring"
The fiche also has labeled the rear drive diagram as a Differential, which it certainly isn't—an example of Germglish 101.
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Alabrew- I'm pretty sure that my sending unit is damaged in some way. But since I haven't seen one that isn't damaged it's difficult to tell. Do you still have your '85 K100? Can you look at the sending unit and see if the flange with the arrow on it has a gap between it and the nut? Like the one in this pic. That would confirm that mine is damaged.
If I can confirm that it's damaged then I can confirm that I need to try something unconventional to fix it. My plan is to first try doubling up the gaskets. Maybe even tripling. If that doesn't work then I'll try the fuel proof thread sealing tape. If that doesn't work then I'll try a fuel proof RTV sealant. And if that doesn't work then I'll try to find a used sending unit, which seems like a difficult thing to find according to my research.
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I'm pretty sure that my sending unit is damaged in some way. But since I haven't seen one that isn't damaged it's difficult to tell.
If you want to compare some, look on the Web. I've seen more of them than I imagined possible with my short attention span, and all of the flanges seemed flush with the nut. That's why using sealant under the flange was suggested if there wasn't enough muscle to push it flush with the top of the nut, or if the flange of the sender was somehow out of square with the sender's body.
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Laitch- I did some searching on the web. Found pics of the sending unit part itself but not installed. So I wasn't sure what it should look like installed.
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Laitch- I did some searching on the web. Found pics of the sending unit part itself but not installed. So I wasn't sure what it should look like installed.
The sender flange is supposed to be flush with the top. If you can't force the cap up to the flange with the sender body inverted then you'll need to try sealing that the gap with RTV or another sealant because that's where you indicate it's leaking. Wrapping the outlet threads with tape or applying paste to them is unlikely to stop a leak from a gap in the flange/nut mating surface. Once you get it installed there is a 50/50 chance it won't work correctly anyway because that style was notoriously unreliable—the reason the float-style was introduced in 1986.
(http://www.motobrick.com/gallery/3/1601-121020001431.png)
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Wheeze - yes, still have the '85, well, two...butts, that's another story.
Yes, there should not be a gap between the stem and nut with a gasket in place.
In your last pic., it really doesn't look like you have it screwed down all the way.
No threads should be visible, especially without a gasket.
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Alabrew- Thanks! I was wondering about the exposed threads as well but forgot to ask about that. I guess that whatever is making it crooked is also keeping me from screwing it down all the way. I'm just nervous to put too much torque in the nut because if I break it I've opened up an even bigger can of worms.
My new gaskets should arrive tomorrow and then I'm gonna give it another attempt.
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I was wondering about the exposed threads as well but forgot to ask about that. I guess that . . ..
There are usually a few exposed threads on the end of a capped pipe. Take a moment to analyze this thing instead of guess about it.
The molded flange of the sender should seat on the top of the gasketed nut. In that position, the sender unit should screw tightly onto the port. There should be no leaks from the around the port's threads nor or the seam between the joint and the cap. You've neglected to answer some questions posed in this thread previously. Please answer these.
- Without the nut on the sender's body, can the sender be pushed into the port all the way up to its flange being level with the port's external opening?
- If No, can you see what is obstructing it by looking into the opening of the fuel tank with its cap assembly removed?
- Can the nut be slid all the way up the sender body until it's surface is flush with the entire underside of the flange.
- If No, what's stopping it?
- If Yes, will the nut stay in that position when the sender is held vertically with its socket upwards?
Tightening the nut is unlikely to draw the sender's body down until its flush with the nut nor prevent fuel from leaking from a gap left between the flange and the nut, as you have described the leak. Excessive tightening could crack the plastic nut.
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Laitch- I'll try to answer in order and as best I can:
1) It is not possible to remove the nut from the sender body. It is captured in between 2 flanges that are part of the sender body. So it isn't possible to insert the sender without the nut. It seems like whatever is causing the sender to seat crooked is between these 2 flanges, and I can't see in there to determine what it is.
2) When the nut is slid up the sender body against the inner flange, it becomes crooked. I can't see in there to determine what is keeping in from seating evenly.
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I took the sending unit off the parts bike last night.
There were some threads still showing while it was installed.
I did not remove the gasket that was installed because I saw there were only three in the bag, I had both 5, so I didn't want to risk damaging it.
With the gasket installed, there is fair amount of friction between the nut and stem.
Are you installing the gasket between the nut and the lower stem flange, or are you attempting to have it seat when you screw it in?
I inserted it inside down to show its correct orientation. =-}
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There seems to be a distinct difference between the depth of Alabrew's sender nut and the depth of Wheezy's sender nut. Maybe that's a function of photo perspective or maybe they are two differing assemblies.
It should be possible to use a thin, angle pick between the flanges surfaces to search for and remove obstructions. It should be possible to inspect through the sender hole and the fuel tank cap assembly hole using a flashlight and an articulating mirror to search for obstructions. It should be possible to try the sender's mounting with the gasket in two different positions as Alabrew has indicated.
If none of this is possible, then buying and installing a used sender and hoping for the best, or sealing that outlet by whatever means are available and computing remaining fuel supply by mileage are other options
Onward!
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Are you SURE you have all the old gasket out?
I seem to remember the nut flopping loosely without the gasket.
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Getts you some lube on the gasket, including the inner diameter (am I the only one missing the Johnny speak here?) so it doesn't bind on the threads and travel up the thread, cocking the gasket with the thread. Push the gasket fully into the nut, past the threads. Push against the electrical socket with your thumb to prevent the gasket engaging with the thread. With your thumb pressing on the socket, then turn the nut. Give that a go. Might be lucky.
If you have the gasket off, check there is no split between flange and sender in case sender goes off right angles, causing the coned part to jam in the tank opening, preventing the nut from compressing the gasket, or all around the gasket.
When it's installed does the unit feel solid inside the tank, or a bit wobbly, in which case maybe it can be straightened to tighten some more.
The gap between the lower flange and the nut is a hint that the gasket might be engaged with the threads.
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FINALLY GOT IT TO STOP LEAKING!!!!!!!!!!!!!!!
Apologies for the delay in getting back to this thread. Last weekend was my son's 2nd birthday and we went camping for the weekend. Then work, house repairs etc. But the good news is that it looks like the leak is finally resolved. After trying various method of trying to stop the sending unit from getting crooked, doubling up the gasket, and using a fuel resistant thread seal tape on the threads, I resorted to the method I was trying to avoid. I used a fuel proof sealant called Seal All. If this had not worked I'd be hoping to miraculously find a used sending unit on eBay.
That particular sealant was recommended by a friend that repairs small engine equipment for a living. He says he's used it to repair plastic and metal fuel tanks, fuel inlet nipples and other parts that are in constant fuel exposure and vibration and has had success with it. Says the repairs have held up over time and use. I used a Dremel with a brass brush to clean and scuff the surface between the outside of the nut and the outer flange. Then further cleaned all surfaces with acetone and compressed air. Then I applied the sealant to both sides of the gasket and to the gap between the outside of the nut and the outer flange. I pushed the sealant into the gap with a cotton swab dipped in a bit of acetone.
The downside of using the sealant is that if I ever have to remove the sending unit for any reason it'll be a bit of a cleanup job. And since the nut no longer will rotate independently of the sending unit, I'll have to disconnect the wires from the fuel pump before unscrewing it. Hopefully this repair holds up long term. I'm excited to finally be able to button this thing up and take it for a first test ride since I bought it.