Modern Vespa

So (what I think is) the "fuel tank float" (005010 in the diagram) leaks gas when I fill the tank really full.

I might ignore this and just fill less full, but since the bike is currently torn down and I'm about to put back together I really don't want to do so if I know it's leaking.

I checked the gasket and it seems totally fine.

Any chance the answer here is "this part always leaks if you overfill"? If not, then would I just need to try to replace the gasket or else the whole assembly?

The float just turns a quarter to a lot into place, so I can't really tighten it any further, so that's not an option.

replace the gasket

it looks stretched which is a sign its lost its elasticity thus leaking.

Thanks! Revisiting this post...I went down a few rabbit holes trying to find a replacement gasket, but long story short it doesn't exist (unless I buy the whole sending unit for >$100, so does that mean I would need to either make my own gasket or else just go to an auto parts store looking for one that'll hopefully fit? I know I need something rated for use with gasoline—beyond that I think I'd just want it to be good dimensions and, obviously, stop the leak itself.

I *think* but I'm not 100% sure that this might work.

https://www.sip-scootershop.com/en/product/gasket-piaggio-fuel-gauge-transmitter_22835400

your sending unit appears to be the same as later ET, LX & GT.

if you can measure it, I'll compare it to the one I have here.

failing that, it's a new unit (which may not be a bad idea considering the whole thing is apart) or make one from a sheet of material.

hth

What are the desired dimensions of the gasket? (Inner radius, outer radius, thickness.)

That thing bears a very strong resemblance to a fork seal's "dust cover," which come in any number of shapes and sizes.

Thanks Greasy and Juan.

So it's actually flatter than that one, Greasy, just a disk. See pics.

Dimensions:
- Width of the RING of the oring is 5mm
- Width (diameter) of the whole oring is 52-53mm. So maybe 55mm for a new one?
- Thickness is 3.5mm. So maybe 4mm for a new one?

https://imgur.com/a/Cpvruil

Also, I'm looking around for some right-thickness o-ring material to just cut it out of. But would need to be rated for gasoline, or so I gather. Haven't found a source for that yet.

I think it's just the picture, they're about 4mm thick new

here's the one I've got

45mm ID
60mm OD

thickness:
4mm outside edge
2mm inside edge

sending unit is 45 ID and 59 OD at the flange



fyi, sending unit is out of an LX150

This would probably work forever, quite a while since it comes in a pack of 10, or long enough to find a perfect flat replacement.

uxcell Nitrile Rubber O-Rings 53mm OD 46mm ID 3.5mm Width, Metric Nitrile Rubber Sealing Gasket, Pack of 10

https://a.co/d/db3vtUP

Thanks so much, Juan. I think you're right that they might last a little while, but since getting to this seal requires taking off a good amount of the body, I'm holding out hope for an OEM-level solution at ModernVespa prices (read: cheap )—these seem to indicate that they'd be OK around oil but not gas, unless I'm misreading it. Thanks though, seriously.

So this is interesting, because that unit does look very similar to mine but, yeah, the ID and OD are different. It does have me wondering if the o-ring I pulled wasn't actually OEM, since yours isn't flat like mine. Wait, so does yours wrap around flange of the sending unit, or how does it work? Now I need to measure/get pic of my sending unit—b/c I think you're right, if they end up being the same unit then maybe I have a weird o-ring in mine!

Do you happen to have a shop manual or could confirm the part number for your sending unit, similar to the pic in my original post? If we confirm they're the same unit then, yeah, I'll just order one of those Meanwhile I'll measure the sending unit on my end and get back to you.

Thanks again!

this is what it looks like installed


the only marking on it is on the top: 09T5A02

the PN I have in my "old book" is CM025702 which is superseded by PI025702 (online)

piaggio lists PI025706 for BV and Fly

the only thing I can assume is that it might be longer? this one measures in at 170mm

Unfortunately, looks like we have different parts. Mine says 2042F06 on the top, the OD of the flange at the top is ~54mm, and the inside is 45mm. I do wonder though if my gasket is supposed to be ridged like yours is or flat like the one I have is.


Update: Found this a from an old thread ( Fuel gauge not working on my "new to me" 04 BV200 ) from 14perry. I PM'd him and hopefully he'll chime in, but looks like he hasn't commented on here since 2019 so guess I won't hold my breath?

"Sending unit is just below the fuel filler cap. You need to remove the entire trim panel that has the fuel door on it. Also you need to be careful with the gasket on the sender. Mine leaked and there was no replacement available for it. We had to flood the top with gas tank repair epoxy."

Seems weird they'd use gas tank repair epoxy, as that would harden and become useless as a gasket, I would think.

I will confess to using a product called "Seal All" on my Scarabeo's fuel pump insert. It looks sketchy, smells suspicious, and the packaging, which hasn't changed since I was a wee lad, evokes the 1950s (predating me by several years). And it seems to be targeted towards the agricultural demographic.

But that was 14,000 miles ago, it has held up on numerous inspections when I've been in that neighborhood, and I haven't given it another thought, knock on wood.

Love epoxy I do very much but I would not use epoxy on that kind of plastics.

Interesting—so does it dry with any sort of give to it, or completely hard? Going this route definitely feels like a bit of a gamble, lol, and maybe couldn't be undone afterward if I mess it up.

It is not as hard as epoxy and I think I could get most of it off with heat and some kind of blade or abrasive tool.

I am not recommending it, just saying.

UPDATE

Ordered this for $18 shipped—leak is the exact same. I think b/c either (a) it's not flat enough or (b) it's not wide enough (and since it's tubular, not flat, (b) is kinda the same as (a)).

https://www.mcmaster.com/o-rings/chemical-resistant-super-resilient-viton-fluoroelastomer-o-rings/

Not sure what to do now. Toying with getting something like https://smile.amazon.com/Neoprene-Supports-Anti-Vibration-Anti-Slip-Protection/dp/B09784Z6WM/ref=sr_1_10?keywords=rubber%2Bsheets%2C%2Brolls%2B%26%2Bstrips&qid=1664430100&qu=eyJxc2MiOiI2Ljk3IiwicXNhIjoiNi44MCIsInFzcCI6IjYuNDIifQ%3D%3D&s=industrial&sprefix=rubber%2Bsheet%2Cindustrial%2C165&sr=1-10&th=1

and trying to cut to size. But of course, the gasket I'm trying to create is a bit thicker than 1/8," so if I go 1/8" I'm afraid it will be too thin. Could go 1/16 and try to do 3 layers, but I've no idea if that would be viable.

Meanwhile, I'm not even finding this part OEM.

Pretty frustrated at this point and very open to suggestions.

Next step is to find a sheet of fuel-resistant gasket material and cut your own out with an Xacto knife. Crude but not too hard.

Word. Hard to find anything that's 4mm thick and will come quick, guess I shouldn't be so impatient, lol. Ordered this and will try to cut 3 of them and stack them (should be about 20% too thick, maybe I can buff them with something to thin them out?) when it comes, hopefully this evening:

https://smile.amazon.com/dp/B0859G62P8?psc=1&smid=A28PJ006KWTLQO&ref_=chk_typ_imgToDp

Use some of the 'Right Stuff' in between the layers and each side. That'll seal it.

Thanks, Jimc. Actually, gasket maker is the kind of solution I'd thought someone would confirm as a good idea (I think I suggested it earlier) so was surprised no one did—I did some research and think the right choice will be the Permatex Permashield.

People said the other gasoline-resistant Permatex solution, Motoseal, is only so-so for long-term gasoline resistance—they recommended Hylomar instead, which I can't get locally, but Permashield says "compare to Hylomar" right on the tube, plus one reviewer on the AutoZone site actually used this to seal up a fuel sending unit!

https://www.autozone.com/sealants-glues-adhesives-and-tape/sealant/p/permatex-permashield-orange-fuel-resistant-gasket-sealant-2-oz/166684_0_0#bv_PDPReviews

I think if I simply applied this to the flange and then installed the flange, then even under best-case scenarios, it would then be very difficult to remove, since the gasket maker would surely drip/be squeezed into the three openings that the sending unit goes into in order to twist into the gas tank. Thus instead I'm going to apply to just the sending unit, upside down, and try to get it as even as possible and at the right height, then let it dry and try it then. If I'm lucky I won't need the rubber I ordered at all and can return it.

an o-ring isn't going to work-- as you found out-- because of the notches in the tank for the tabs on the unit to engage.

the gasket has to be flat.

this would probably work:

https://www.mcmaster.com/gaskets/gasket-material/chemical-resistant-viton-fluoroelastomer-gasket-material-6/

(1084N83)

it's a little thin, but I'd add some sealer to it on both sides.

either permatex Motoseal, permatex aviation #3, or the permashield 85420

whatever you do use has to be gasoline resistant

I'd see if I could use two pieces of sharpened pipe to punch out the gasket on a wood block

another option in the same vein is to peel thru the felpro catalog or amazon and see if you can find something that meets the criteria and doesn't break the bank. some of the options I saw were damn near 1/2 the cost of a new sending unit.

Yeah at this point I'm about $64 in, but hopefully might recoup $30 if I'm able to make due with just the permashield.

I actually don't get what you mean about the tabs, but I do agree that the thing needs to be flat—I thought the one I got from McMaster was a "flat o-ring" but I was wrong .

for all the argle-bargle ya could've just popped for a new sender and been done!

all kidding aside, I get where you're coming from.

mcmaster does sell the "square" o-rings but they are super skinny so you likely would've had the same problem.

by tabs, I meant the notches is the fuel tank where the tabs engage to lock it into place. it creates kind of a no-man's land there for an o-ring to roll right into and nothing seals at all. I think I need another cup of coffee...

Re: a new sending unit instead: yeah, don't remind me! But have you actually seen any that say they'll work specifically with an 03 200 Beverly?

Tabs: Yes, exactly! Therein is one of the rubs.

https://www.sip-scootershop.com/en/product/fuel-gauge-piaggio_PI025706

spendy, but there you have it.

or gamble for a little less:

https://www.ebay.ie/itm/354052335976

Last edited by greasy125 on Fri, 30 Sep 2022 00:21:05 +0000; edited 1 time

Ah nice thank you—and look, it's some sort of tri-pli gasket, seemingly!

SUCCESS!!

Thanks so much everyone! If anyone else needs some of this gasket material I bought? I have a whole roll now, just let me know


Doesn't look like this will work…and it definitely didn't!

Cutting the rubber—found a plumber's tape roll just slightly larger than the sending unit's diameter, traced it and cut it small—good fit!

Did 3 layers of 1/16th—a tight fit!

Installed—note that I left a very thin lip of the gasket extending past the edge of the sending unit flange. This bit got pulled up when I reinstalled, making what I think is a fantastic seal.

That really looks great!

nice! fingers crossed that you don't have to revisit it!