Topped off Primavera fuel tank not reading full
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Member
2015 Vespa Primavera 150
Joined: 17 Oct 2019
Posts: 20
Location: Long Beach Island
Wed Dec 25, 2019 9:01 pm quote
Not that big of a deal but just curious.

I topped off my 2015 Primavera 150 and added fuel stabilizer the other day at the gas station. When I started it up the fuel gauge read one bar away from a full tank reading. I figured it would correct itself and move to full when I rode home about 1 mile away but it still has not read full. It is definitely full to the very top since I can see the fuel with the cap off.

I never let the tank get too low but was wondering if the fuel low light would show up early because of the reading being slightly off or is the lower tank reading more accurate than the full one.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2977
Location: East Anglia, a dryer region of the UK than Israel
Thu Dec 26, 2019 2:29 am quote
Probably either the float in the tank is stuck, this can happen if the bike has stood for long periods in its history. Or the sender unit in the tank itself is now going faulty, or the gauge itself is going faulty. It's anyone's guess as to how accurate the gauge will be as the fuel level drops. You could try rocking the bike vigorously back and forth with the front brake applied firmly. This is often more effective when the tank is nearer 3/4 full. This will move the float and arm rigorously up and down and may fix it. If not check the resistance at the gauge. Specs should be in the workshop manual. Good luck! Let us know how it goes.
Ossessionato
LXV 150 3v ie. Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 3409
Location: Bangkok
Thu Dec 26, 2019 2:56 am quote
What did it do before you added the batch with stabilizer?
Member
2015 Vespa Primavera 150
Joined: 17 Oct 2019
Posts: 20
Location: Long Beach Island
Fri Dec 27, 2019 12:15 am quote
waspmike wrote:
What did it do before you added the batch with stabilizer?
I never topped it off to the fullest. Usually put $4 premium gas when it gets close to a quarter tank. It would read two bars from full tank.
Ossessionato
Yamaha Tricity 155 Urban 2019 - MV Agusta 125 RS 1956 - Yamaha Majesty 250 DX 1998
Joined: 21 Jul 2007
Posts: 3959
Location: Latina (Italy)
Fri Dec 27, 2019 12:25 am quote
Simple, make a stick with drawn notches on it and every now and then make a visual check; if you don't notice any difference between one measurement and another, it is fine.
Ossessionato
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 2977
Location: East Anglia, a dryer region of the UK than Israel
Fri Dec 27, 2019 1:41 am quote
Sludog wrote:
waspmike wrote:
What did it do before you added the batch with stabilizer?
I never topped it off to the fullest. Usually put $4 premium gas when it gets close to a quarter tank. It would read two bars from full tank.
In that case, it's likely to just be the sender unit sticking. If you've never filled the tank or very rarely, the sender unit is encountering sticky fuel debris near the top of its travel. It will probably sort it's self out if you fill the tank a couple of times, but try the vigorous rocking of the bike when the fuel level drops to about the 3/4 level. Once you have used most of the stabil treated fuel up refill but add some seafoam. This is very good at dissolving the sticky gum produced by modern petrol. It's most likely this sticky muck causing your issue.

CAUTION: do not add Seafoam until you have used up nearly all the Stabil treated fuel in the tank first. If you do this may adversely affect the engines fuel mixture control.
Hooked
Vespa Primavera 150
Joined: 27 Mar 2014
Posts: 159

Sun Jan 12, 2020 4:18 pm quote
The exact thing happened to my 2015 Primavera. The cost of replacing the float or any other part is cost prohibitive. Every so often the gas gauge shows full bars after a fill up, but it is usually stuck one bar below full. I find it annoying. I brought my scooter brand new and have had at least two expensive repairs done. Not sure they are as reliable as the cost would indicate. But we love to ride, and there is nothing quite like a Vespa.
Enthusiast
Vespa Sprint 150
Joined: 17 Jan 2019
Posts: 82
Location: Portland OR
Mon Jan 13, 2020 4:11 pm quote
I don't bother with the gas gague as gosple, instead use I one of the trip meters because that's reliable. Reset when full, I fill up some time between 100-120mi and I put in some where between a 1.2 and 1.5 gal on a stock sprint 150.
Hooked
2016 BV350 White
Joined: 01 May 2010
Posts: 378
Location: East LA County, CA, USA
Mon Jan 13, 2020 8:44 pm quote
How do you fill up your scooter? On the side stand or center stand? I sometimes have the same issue. When on the side stand I tilt my scooter up and let the gas settle in the baffles and repeat until it won't fit anymore gas. Sometimes I also jiggles my scooter a little to help the gas settle into the baffles.
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