Author Topic: 78 550K leaking fuel after carb service  (Read 3531 times)

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Offline DaveBarbier

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Re: 78 550K leaking fuel after carb service
« Reply #25 on: July 10, 2018, 03:46:44 AM »
Someone mentioned the floats are “solid” yet to float they must trap air in the solid material to float.

To float, an object only needs to weight less than the amount of fluid it displaces. Doesn’t have to contain air at all. Even an anvil will float on a sufficiently dense liquid like mercury.

Offline BRG-BIRD

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Re: 78 550K leaking fuel after carb service
« Reply #26 on: July 10, 2018, 05:02:45 AM »
Gasoline is not very dense at all.
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Offline flybox1

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Re: 78 550K leaking fuel after carb service
« Reply #27 on: July 10, 2018, 05:59:31 AM »
I would move your floats to different carbs to see if the problem follows the floats. Someone mentioned the floats are “solid” yet to float they must trap air in the solid material to float, they can absorb ethanol and become too heavy.
Buoyancy...and yes, solids can float.

The black floats are solid.  Let me find my broken one.....
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline DaveBarbier

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Re: 78 550K leaking fuel after carb service
« Reply #28 on: July 10, 2018, 06:06:13 AM »
Gasoline is not very dense at all.

Yet it doesn’t require air to be inside something for it to be able to float. That’s all I’m saying. I don’t think these black floats can get fuel inside them. I think they’ll always float.

Offline BRG-BIRD

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Re: 78 550K leaking fuel after carb service
« Reply #29 on: July 10, 2018, 03:58:46 PM »
Well just trying to help based on real experience. You should though ask yourself why does one type of solid wood weight more than another? Why does it not always float after being in water for an extended period of time? Is metal solid? Could it be porous?

Anyway hopefully the OP will get his bike up and running properly soon. :)
“You are either on something or onto something.” The Comman Man

Offline TwoTired

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Re: 78 550K leaking fuel after carb service
« Reply #30 on: July 10, 2018, 09:01:28 PM »
Material science has recognized that a given material can be more or less dense WITHOUT having air incorporated.
Yes, some materials can have air in them.
Many floats in carbs are made of a man made material, and it is not organic.  I've never seen a plastic float in an SOHC4 sink because it soaked in fuel to change it's boyancy.

Gasoline is lighter than water and floats upon it.  This is because it's molecular structure, makes the substance lighter than more densely compact water molecules.  Interestingly, water can hold air in suspension.   Gasoline still floats upon it.

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Offline DaveBarbier

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Re: 78 550K leaking fuel after carb service
« Reply #31 on: July 11, 2018, 02:20:53 AM »
Well just trying to help based on real experience. You should though ask yourself why does one type of solid wood weight more than another? Why does it not always float after being in water for an extended period of time? Is metal solid? Could it be porous?

Respectfully, for a better understanding of buoyancy I suggest auditing an 8th grade science class.

Offline brewsky

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Re: 78 550K leaking fuel after carb service
« Reply #32 on: July 11, 2018, 03:41:02 AM »
  Even an anvil will float on a sufficiently dense liquid like mercury.

That analogy will be hard to forget!
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Offline flybox1

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Re: 78 550K leaking fuel after carb service
« Reply #34 on: July 11, 2018, 07:01:08 AM »
These last few posts were a good chuckle... ;D

I always remember the photo from grade school of a British pound coin floating on top of Mercury.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline brewsky

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Re: 78 550K leaking fuel after carb service
« Reply #35 on: July 11, 2018, 09:40:43 AM »
Here is what the float looks like immersed in gas and how the fuel level translates to the outside of the bowl.

This is with the float set at 14.5mm per '78 spec. for 750K

The level may be a millimeter or 2 off due to measurement error :-\

Note these are from a 750, but the 550 carbs are similar
66 CA77
78 550K
78 CB750K
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09 GL 1800

Offline BRG-BIRD

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Re: 78 550K leaking fuel after carb service
« Reply #36 on: July 11, 2018, 07:01:33 PM »
Let's see what the OP comes up with. I have no problem being an outlier which can flip some out, a little out of the box thinking doesn't hurt.
“You are either on something or onto something.” The Comman Man

Offline calj737

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Re: 78 550K leaking fuel after carb service
« Reply #37 on: July 12, 2018, 11:31:42 AM »
stick your thumb on the overflow hose,if the seats are leaking the carbs will fill up and leak elsewhere,if it stops you have very fine cracks in those brass overflow tubes.
Also referred to as the "Little Dutch Boy" test  ;D
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Offline dave500

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Re: 78 550K leaking fuel after carb service
« Reply #38 on: July 12, 2018, 12:55:41 PM »
why didn't strynboen or deltarider mention it then?

Offline spanners

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Re: 78 550K leaking fuel after carb service
« Reply #39 on: July 13, 2018, 10:11:11 AM »
Because sticking your fingers in Dykes, no matter what the emergency is probably banned by H&S regs these days in Holland  ;) ;)
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