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General Category => General Discussion => Topic started by: Thirtyaughtsix on July 14, 2018, 04:52:01 AM

Title: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 14, 2018, 04:52:01 AM
So it turns out my gas tank is evaporating no less than a half gallon of premium here in the summer if I let the bike sit for a full day and that's my very generous guess, I honestly think it's closer to a full gallon. Ran out of gas riding around the other day and had to throw the petcocks on reserve to get home, much to my surprise as I though I had 5 gallons remaining, was luckily not even a mile from home. Gas tank is an 850T original, other than my paint job and mgcycle gas cap that's maybe a year old.

Obvious question is, what can I do to prevent this?
Title: Re: Evaporation from fuel tank
Post by: Aaron D. on July 14, 2018, 05:19:59 AM
Please take this in the spirit offered.
No way in hell is your tank losing that much in evaporation in a day. Check your oil level to see if it has risen, and find the leaky petcock.
Title: Re: Evaporation from fuel tank
Post by: yogidozer on July 14, 2018, 05:32:03 AM
What Aaron said...or, maybe you were riding further than you thought you were?  :wink:

(https://thumb.ibb.co/dtVUGo/mu.png) (https://ibb.co/dtVUGo)
Title: Re: Evaporation from fuel tank
Post by: Tom H on July 14, 2018, 11:31:44 AM
Please take this in the spirit offered.
No way in hell is your tank losing that much in evaporation in a day. Check your oil level to see if it has risen, and find the leaky petcock.

Had that happen to my Eldo. I was on a trip and stopped for lunch and left the petcock open. Then probably went about 100 miles. Decided to check my oil and it came pouring out the dip stick hole. Probably had the cleanest engine out there! I did do an oil change at the first parts store I found.

Tom
Title: Re: Evaporation from fuel tank
Post by: Wayne Orwig on July 14, 2018, 11:39:44 AM
Agreed.
If the petcock was on, or leaking, a leaking float was pouring gasoline past the rings into the oil. Sniff the oil. That will damge the rings quick too.



Title: Re: Evaporation from fuel tank
Post by: Huzo on July 14, 2018, 04:51:18 PM
Is there no overflow on the bowls anymore as in days of yore ?
Title: Re: Evaporation from fuel tank
Post by: Tom H on July 14, 2018, 09:28:21 PM
If the bike in question has the VHB carbs. There is an overflow hole. But it it's not leaking badly, the gas can slowly flow into the cylinder through an open intake valve and make it way into the crankcase.

Tom
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 15, 2018, 06:05:52 AM
If the bike in question has the VHB carbs. There is an overflow hole. But it it's not leaking badly, the gas can slowly flow into the cylinder through an open intake valve and make it way into the crankcase.

Tom


(https://thumb.ibb.co/gK18ST/37206096_10216504105616010_3960508202566549504_n.jpg) (https://ibb.co/gK18ST)


You talking about that hole about halfway down then? Both sides are like this, lower half covered in a film of fuel. You may have to forgive my ignorance here, but I had always thought this was just a thing that was natural for all old carburetors to do lol
Title: Re: Evaporation from fuel tank
Post by: yogidozer on July 15, 2018, 06:09:40 AM
so, was their fuel in the oil?
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 15, 2018, 06:19:27 AM
so, was their fuel in the oil?

Not that I could tell, no. She's due for a change and was a little below the 2nd line, no gas that my nose could detect
Title: Re: Evaporation from fuel tank
Post by: Chuck in Indiana on July 15, 2018, 07:50:59 AM
Agreed.
If the petcock was on, or leaking, a leaking float was pouring gasoline past the rings into the oil. Sniff the oil. That will damge the rings quick too.

And the main and rod bearings. Don't ask me how I know..
Title: Re: Evaporation from fuel tank
Post by: RinkRat II on July 15, 2018, 11:35:15 AM

       
Quote
Obvious question is, what can I do to prevent this?

    Double check that your cap has some type of pressure/vacuum relief valve . Most newer caps have vacuum and  pressure relief valves built in to prevent evaporation but still allow fuel to flow to the carbs.  Your system may be old enough when they didn't have this feature and there is little you can do to stop it.
   If it's any consolation, this time of year in Arizona  My Sport evaps out about a half gallon over a weeks period of time.  Gas ain't what she used to be!

          Paul B :boozing:
Title: Re: Evaporation from fuel tank
Post by: redrider90 on July 15, 2018, 12:33:37 PM
It is highly unlikely that it is leaking past the carb into the crankcase. The OP said he may loose as much as a gallon a day and yet the engine runs. I think an extra gallon of fluid to the crankcase would cause the engine to hydraulic and end of story.
I had that happed to a 13 HP B&S lawn mower engine. One day I go out to mow the law and got about 30 feet and it threw a rod broke a hole in motor.
I said what just happened here. I'm thinking no oil and I pulled the dipstick and it was full to the top. I smelled it and it was gas. I open the gas tank and it was empty. My float had stuck over the previous week or so since last cut. It made quite a racket when it blew while I was sitting on it.  :grin:
Title: Re: Evaporation from fuel tank
Post by: yogidozer on July 15, 2018, 12:37:44 PM
sure your wife isn't draining it so you'll mow the lawn?  :laugh:
Title: Re: Evaporation from fuel tank
Post by: Triple Jim on July 15, 2018, 01:18:45 PM
(https://thumb.ibb.co/dtVUGo/mu.png) (https://ibb.co/dtVUGo)

Great song, Yogi!
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 16, 2018, 06:55:20 AM
sure your wife isn't draining it so you'll mow the lawn?  :laugh:

Positive, we rent currently so neither of us have to mow lol
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 17, 2018, 10:19:39 AM

(https://thumb.ibb.co/kFiPpJ/37217427_10216523387178037_3293873731415310336_n.jpg) (https://ibb.co/kFiPpJ)


Think I found my problem lol, to think it's gone 700ish miles like this. I say this as I took it to a shop to tune it for me cause I had known the bike had always ran rich in my time with it and could never get to the bottom of it, I guess the shop couldn't either
Title: Re: Evaporation from fuel tank
Post by: yogidozer on July 17, 2018, 11:30:28 AM
plug on the left looks like there is no gap? could be the angle
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 17, 2018, 12:09:27 PM
plug on the left looks like there is no gap? could be the angle

It's the angle I promise, it threw me for a sec too before I snapped the pic
Title: Re: Evaporation from fuel tank
Post by: pehayes on July 17, 2018, 12:27:19 PM
Think I found my problem lol, to think it's gone 700ish miles like this.

When people write about spark plug issues I always refer to this:

http://www.guzzipower.com/Sparkplug-pehayes.html (http://www.guzzipower.com/Sparkplug-pehayes.html)

My Guzzis have always been happy.
EF, SPII, Convert, Eldorado, V50, V65

Patrick Hayes
Fremont CA
Title: Re: Evaporation from fuel tank
Post by: Huzo on July 17, 2018, 06:05:23 PM

(https://thumb.ibb.co/kFiPpJ/37217427_10216523387178037_3293873731415310336_n.jpg) (https://ibb.co/kFiPpJ)


Think I found my problem lol, to think it's gone 700ish miles like this. I say this as I took it to a shop to tune it for me cause I had known the bike had always ran rich in my time with it and could never get to the bottom of it, I guess the shop couldn't either
Are they both the same reach ?
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 19, 2018, 09:34:42 AM
Are they both the same reach ?

How far off from each other would they have to be for it to concern me?
Title: Re: Evaporation from fuel tank
Post by: RinkRat II on July 19, 2018, 10:06:41 AM
 
  Depending on what plug is called for for your bike,  that is the plug you need to use. If one of your plugs is 3/4 reach and the other is 5/8 that is unacceptable. Plugs are designed to allow the tip or electrode to just sit inside the chamber to ignite the fuel, if it doesn't and sits up inside the threaded portion it won't ignite the fuel properly. Conversley if it's too long it may damage the piston should it hit the plug.

       Paul B :boozing:
Title: Re: Evaporation from fuel tank
Post by: rodekyll on July 19, 2018, 04:19:04 PM
RR is pranking you.  AOf course they do.  The ngk part number tells you the thread diameter, Length, heat range, tip type, resistance, etc.  There is nothing random about them.  All B6ES are identical.
Title: Re: Evaporation from fuel tank
Post by: Thirtyaughtsix on July 20, 2018, 07:34:44 AM

  Depending on what plug is called for for your bike,  that is the plug you need to use. If one of your plugs is 3/4 reach and the other is 5/8 that is unacceptable. Plugs are designed to allow the tip or electrode to just sit inside the chamber to ignite the fuel, if it doesn't and sits up inside the threaded portion it won't ignite the fuel properly. Conversley if it's too long it may damage the piston should it hit the plug.

       Paul B :boozing:

Oh no it's nothing like that, they're both the same plug out of the same box. Like I'm sure they're not perfectly equal as I had to gap them but I'd think only a pair of calipers would be able to tell
Title: Re: Evaporation from fuel tank
Post by: RinkRat II on July 20, 2018, 09:37:32 AM

   Good to know, a few thousands here and there won't matter but if someone had installed the wrong plug that would be trouble.

       Paul B  :boozing: