out of fuel, no warning light

weird, 160kms since I last filled up, no fuel light on the dash, riding through town and bike starts to miss. Luckily was just by a fuel station. bike completely cut out about a hundred metres away so I could coast in.

Filled it up with either 14 or 16litres, can't quite remember and then rode away happily.

I usually get better mileage than that. All I can think of is that I was away for 3/4 weeks so couldn't ride, maybe it was shitty fuel and the ethanol has evaporated to the point that it was uncombustible or something. (can you tell I'm clutching at straws here!!?)

but that doesn't explain the warning light not coming on

anyway, so so pleased to be back on the GRiSO and hoping they don't grit the roads this weekend.

thoughts welcome

If the tank was full that's some lousy economy! I get about 300km from a tank in normal riding.

The light is operated by a thermistor that illuminates the light when no longer submerged. They do fail occasionally.

300km?????? I take it that's theoretical...

We have the same motor and the same beetle map and same exhaust,

my fuel light usually comes on at 180kms ish which I ignore as if I fill it then I can only get 10l in. So maybe we're getting around about the same mileage

digression aside, it's really weird that A the fuel light didn't come on and B it ran out so soon. maybe I was on the wrong trip meter or something, left the bike in the workshop that I share, someone could have flicked the switch while moving the bike or something....

In warm weather, (Not super-hot, just 30-32*C) I usually get 230km before the light comes on and have about 4.5 litres 'Reserve' so 300 is maybe a little conservative if anything. I do ride like the grandfather of the oldest man in the world though. If I press on a bit and in the colder months fuel consumption is considerably higher.

This bit of the GRiSO is determines fuel consumption.


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As for your fuel level sensor, you can measure it so see if it's the sensor, or maybe a connection issue.


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thanks guys, yes I'm a very happy chappy with the go handle once she's warm

Typically 220kms on mine before the light comes on. I ride in mainly mild conditions i.e. 15-25 degrees C.

My fuel light has packed up too. So I rely on the odo for now. My mileage is shocking. I get about 70 miles until the light (used to ) come on, with mostly enthusiastic urban tomfoolery. On runs out of the smoke, it's much better, even at quite high speeds (and I don't mean 130 mph here - but at 80-90 and occasional 100 mph cruising).

Something definitely wrong there.

Since new this motor has done about 25 mpg with enthusiastic urban riding in heavy traffic, and 35-40 mpg when stretching her legs. It's been pretty consistent over 60k miles.

Sounds like mine - crap used enthuasically locally & much better on long trips when not caning it too much. Can't give you an mpg for local as it's less stressful to not check it, but long trips I can get up to high 40s mpg cruising at speed limit.

fuel pump ?
i had issues with fuel pumps on ktm sm950 and 690

Mine drinks hard -28-35mpg (British) for the first 30 miles of any day.
 then settles down to 47mpg for the rest of the day.

(If two up above 5000 revs 42mpg)

I also ride like an old geezer. My reserve light comes on at about 240 - 260 and I'm good for 60km after that.

If you replace the thermistor part of the fuel pump assembly also put in a new fuel filter. My fuel filter lasted 50,000 miles with California fuel until it started to give me problems (blowing the fuel pump fuse).

Have you seen the cost of these parts? I'm shocked. Over 200 of your Earth Pounds for the level sensor from Fowler's. I thought they were avvin a giraffe. (Sorry for the argot - I will translate. I thought they must be joking).

What's the part number?

Forget it. What about this?

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Not quite as spendy.

Pete, thanks for the link. If you read the description of the part, it explains the theory of operation very nicely. Even this dumb old farmer can understand it.

If you want to fix it yourself, this thread covers how I did it on my Breva. It should be the same for the GRiSO.
Breva thermistor thread

The variation in pricing is incredible. Are these all the same part?I can't find it on Fowler's now, of course, but it's offered at £195 here: [You must be registered and logged in to see this link.]

It's a shitty thermistor. I cannot believe that Piaggio use some weird, specially ordered, thermistor with some utterly different heat decay curve. Why would they specify something weird and expensive when they can use something that wholesales for, (At a guess?) three dollars and then flog it to mug punters for $200?

Capitalism works both ways. They try and screw us! We retaliate by finding better, cheaper alternatives!

Shit like roller camboxes? Different matter, (although you can bet they are making a 300+% mark-up on them too!) but a shitty thermistor? Get fucked!

I couldn't agree more. I don't want to shell out 200 notes when I can get something that works well for a quarter of that. But how do you tell if the cheaper parts are going to fit and work on the GRiSO? The part you linked to is out of stock (mind you, so are Fowler's et al).

If you do a worldwide search for "Thermistor Fuel Sensor" on eBay, you get a bunch of hits that look the same as the one Pete posted.

..and that seller has a website where they are apparently in stock.


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And you buy one for a tenth of the price of the non existent factory one, look at how it is installed on the pump assembly, replicate its mounting so it sits at the same height in the tank and solder it in.

Does it work? Almost certainly yes. And if you can verify the resistance at temperature you'll know it will. I personally wouldn't be bothered with that. I'd just fling it in and try it. It can't harm anything. It'll either work or it won't. If it doesn't you've wasted a few quid. If it does you've saved enough for at least a pub meal and a good bottle of plonk to share with the missus.

No brainer to me.