Topic: Too much head!!

[bollingball]

That got your attention. I was doing my 3K tuneup in prep for installing HondaMans Ign box. New points,condensers, and all the other stuff that goes along with it. I was using my aux. fuel tank that I hang off the tracks of my garage door. The tank is about 8 feet up and had about 1 gallon of gas. A few hours laterI found my oil to the top of the tank. Gas in the oil tank. I am thinking there was to much head pressure and over riding the float valve. What say you. I have no problem with the oem tank hooked up. I will change the oil and filter. Has anyone else ran into this?

Ken

[NewOldSchool]

Sounds like the pressure from the tank pushed past the floats/ fuel stops, flooded the cylinders and leaked? past the rings filling the engine with fuel....

I'm confused as this sounds crazy impossible to me?

[LesterPiglet]

Sounds plausible to me. There must be quite some pressure from a gallon of fuel 8 feet in the air all pushing down through that tiny tube.

[Greggo]

Better add a second oil change to that 3k tune

[TwoTired]

Remember how easy it was to push in those tiny spring pins on the float valves?

Note the the I.D. of the hose, and realize that the column of fuel inside that hose has weight.  The volume of fuel from the float valve to the top level of the liquid will push on that spring pin.


(btw, you need and extra o in "to".  )  Seems topical, IYKWIM AITYD. 

[aperry]

Did you have gas all over the floor?  I'm not familiar with your carbs, but one mine I think this lead to a lot of gas exiting through the overflow tubes.

Aaron

[NewOldSchool]

Did you have gas all over the floor?  I'm not familiar with your carbs, but one mine I think this lead to a lot of gas exiting through the overflow tubes.

Aaron

Thats what I thought was so weird?! I would think the gas would be all over the floor.

[flybox1]

Yep, did this on my 350F.    but it came out my overflow tubes. 
I had hung my aux tank up off my garage door runners.
now, my aux tank sits on a rolling too chest next to my bike, just in front of my bars with the shortest fuel line I could work with.
bummer if you had already covered the oil change in your tune up. 

[bollingball]

Did you have gas all over the floor?  I'm not familiar with your carbs, but one mine I think this lead to a lot of gas exiting through the overflow tubes.

Aaron

No gas on the floor. When I started it up to dial in my adjustments I shut it off and out of habit I check the oil and it was at the top of the tank Then I took a whiff. I looked up at my tank and saw it was half empty. Just wanted to bring it to attention to others to look out for.
 TT that makes perfect sense.
 Greggo Yes I will make sure I flush it out. Thanks for your input.
 I'm not that good at math. But I was thinking 5 gallons about 6" above the carbs versus 1 gallon 6 to 8 ft. above ? the same or more?

Here is a pic of the setup.

Ken

[bollingball]

Now I don't know why fuel did not come out the overflow tubes they are clear. These are PD 42b carbs on a 78 750K. Floats are just at 14.5mm Fuel level is about 3mm below the bowl gasket. I am still working on this shooting for 4mm. This does seem odd. Any ideas?
Ken

[aperry]

Did you have gas all over the floor?  I'm not familiar with your carbs, but one mine I think this lead to a lot of gas exiting through the overflow tubes.

Aaron

No gas on the floor. When I started it up to dial in my adjustments I shut it off and out of habit I check the oil and it was at the top of the tank Then I took a whiff. I looked up at my tank and saw it was half empty. Just wanted to bring it to attention to others to look out for.
 TT that makes perfect sense.
 Greggo Yes I will make sure I flush it out. Thanks for your input.
 I'm not that good at math. But I was thinking 5 gallons about 6" above the carbs versus 1 gallon 6 to 8 ft. above ? the same or more?

Here is a pic of the setup.

Ken

I am not sure the weight of the gas column matters all that much.  Most of the weight of that 1 gallon is supported by your garage door anyway.  It's the pressure buildup that really makes a difference.  The pressure is proportional to the height only.  It has nothing to do with the diameter of the column or the amount of gas in the container at the top (except if it adds more height).  In this case, 8 feet would indeed put a lot of pressure on your carbs. 

If you've ever seen an 8-foot aquarium then you've probably notice how very thick that glass is.  This doesn't have anything to do with the volume of water or width of tank.  It's all about the height.

PS:  I am still very puzzled as to why nothing escaped the overflow tubes.  I mean, I would expect it to still be leaking when you entered the garage.  You're certain no PO blocked those things up?  I see it mentioned on the forum from time to time (seems like a terrible thing to do).

[Lostboy Steve]

Clearly i am in the wrong forum

[CrankyOldGuy]

hmmm ...  34 feet of water is approximately one atmosphere (14.7 psi).  If gasoline has a specific gravity of 0.75 then a head of 45 feet of gasoline would be approximately one atmosphere (14.7 psi).  Therefore 8 feet of head of gasoline would result in a pressure of approximately 2.5 psi (360 lbs./sq.ft.) give or take.

Note: no calculator was used just the old brain ... therefore the accuracy may be limited  .

Harry O.

[CycleRanger]

Yeah, try to keep the baby bottle the same height as the fuel tank to maintain similar hydrostatic pressure.

[Frostyboy]

Clearly i am in the wrong forum

  Me too, I never thought you can get too much.

[Retro Rocket]

To much head!!

Yep, no such thing....

[dave500]

Clearly i am in the wrong forum

  Me too, I never thought you can get too much.

mr guillotin had tee shirts made?now thats revolutionary!