gas cap importance

I went out to my swing to add stabil for winter storage. It was crowded in the storage unit so I had to squeeze beside the machine and at an awkward angle unlock the cap. After adding the stabil I put the cap on crooked but didn't notice. I only know that when I tried to start the engine it cranked but wouldn't "catch."
After trying several times I gave up to save the battery. This morning at 3AM it suddenly occurred to me that, just possibly, I had placed the cap on "crookwards."
So this morning at a civilized hour I went out, took off the cap, and carefully put it on straight. The scoot started up!
Has anyone else had this happen???

Nope!

As a general question, isn't the 'Wing' fuel system pressurised? That would explain the starting problem if it was.

u p tom wrote:

Has anyone else had this happen??

If the question is for "finding a solution to a problem at 3AM" ... then yes. :lol!:

If the question is for "not start starting due to the gas cap incorrectly installed" ... then I believe you are the first.

Waspie wrote:

Nope!

As a general question, isn't the 'Wing' fuel system pressurised? That would explain the starting problem if it was.

I suspect not, because it is not a "screw-on" type of cap.

joncallihan wrote:

Waspie wrote:

Nope!

As a general question, isn't the 'Wing' fuel system pressurised? That would explain the starting problem if it was.

I suspect not, because it is not a "screw-on" type of cap.

What makes me think it may be pressurised is that when I fill up and rotate the fuel cap there is a slight hiss from escaping air from the tank. So it must be slightly pressurised!!!!!

Methinks I may have to read the manual in the morning, (If I remember).

What makes me think it may be pressurised is that when I fill up and rotate the fuel cap there is a slight hiss from escaping air from the tank. So it must be slightly pressurised!!!!!

Methinks I may have to read the manual in the morning, (If I remember). [/quote]

Had this event happen on my then wife's car. It would hiss when you undid the gas cap. Turns out it was actually a vacuum, as a mech explained to me, if the tank was pressurized, you would be hit with a very strong gas smell, since you would be venting 100% vaporized gasoline, made sense to me! Turns out the mechanism in the cap that allows air to replace the volume of gas removed was clogged, actually causing a vacuum in the tank, and that is what i was hearing. It also explained why the fuel pump failed since it was trying to overcome the vacuum, as well as pressurizing the system, which happens between the fuel pump valve and the fuel injector.

just my .02

Just went out to the garage and removed the gas cap and put it on my work table. Then I started the scooter and let run for a minute with the gas cap off. The gas tank is NOT pressurized at all to run. If your scooter did not start then it was something else wrong.

It may not be relevant but Piaggio X9s sold in North America have a thing fitted in the tank vent system which can become blocked.
I've trawled throught the forum and found thee three posts (in different threads):


The US models have carbon canister emission vent systems so could be worth investigating but I don't know where to start here, as we don't have them, our tanks just vent to atmosphere with a looped hose.



The charcoal canister won't affect the mixture as it is only in the tank expansion vent system, but the tank uses the vent to breathe as the level drops, so if the system is restricted you could get a slight vacuum in there.



IIRC, someone else had fuel starvations problems recently; also in the States.
It was caused by a partial vacuum in the petrol tank - blocked breather or something - I forget.
Might be worth a look.
There was the sound of air rushing in as the cap was loosened, at first thought to be air rushing out!



The cure was to drill a very small hole in the cap!

Tagg wrote:

Turns out it was actually a vacuum, as a mech explained to me, if the tank was pressurized, you would be hit with a very strong gas smell, since you would be venting 100% vaporized gasoline, made sense to me!

I was kinda correct then.

It was a negative pressure and not positive pressure that was causing the hiss when removing the cap.

At least that is cleared up now. Thank you.

So a little like the Burgman 'burp', we've got the Silverwing 'sssssssssssss'!

I think I was thinking of the note on my car's gas cap that says turn cap until it clicks or malfunction indicator lamp may come on. The scoot wouldn't start and it might have been the moist conditions or something else. I will try it again today if it isn't snowing too much (door gets frozen shut) to see if it starts again. Thanks for the help.

I don't see any way the cap can prevent the scooter from starting. The cap is vented. Try blowing through the raised section of the cap that extends into the tank. Air will pass both ways on my SW.

The scooter has started twice since I had the trouble. Thanks for your valuable research and opinions. I think now it must have been moisture. I started it this afternoon then turned it off, kissed it good-by and closed the door. It will be a long winter....

x

Don't feel too bad about storing your SWs. I'll ride mine some extra for you guys in the cold North!

x

In Marquette the release from hibernation is in late May or early June usually. When I bought my Reflex in '04 it was June. Last spring it was mid-May. Probably that global warming thing... or something similar. Maybe just yearly seasonal fluctuations. Whatever.
The Reflex is being sold by a friend (I can't sell nuthin'). My SYM 250 is also in the shed but has an insufficient windshield suitable only for warm weather. The swing has a givi good for cooler temps. That will be the one coming out, probably in May. Think then I will head south then for a week or two.
Hope I'm not the one considered a wise a--.

x

bigbird wrote:

No, that was for Exavid rubbing it in a bit for us who can't ride for many months. It was meant for him in jest.

Have you thought of accidentally storing your Silverwing on Excell's trailer when he heads to Texas :lol!:

x

Better to be a smart ass than a dumb ass! BTW - I earned my snow-less existance after 36 years in Alaska. :lol!: