How buoyant are the carb floats

[Guest]

I have Gs850n with slider carbs , i would like to know how buoyant these floats are ,any pics or info would be great. The reason I am asking is that the bike is leaking fuel through the overspills. I have rebuilt carbs (except for the floats) they are super clean and the float levels are spot on ( i had to increase the the height of the floats by a couple of mm to get the floats levels in spec). The engine runs fine, then after 5 miles or carbs starts leaking fuel out of the overflows it is totally random which carbs leak..After the third strip down I am at a loss, and any help or ideas would be great. I have soaked the floats in petrol tested for leaks with hot water method. The floats look ok but to me they do not look very buoyant when floating in petrol with only 8 to 12mm sticking out of the petrol. Tank is clean and has never been petsealed, filter on petcock is clean , petcock has been serviced with a kit . If i had hair it would have been pulled out. Thank's from Derk

[fastbysuzuki]

I cannot comment on the floats other than if you have tested them and they do not leak (petrol inside) then should be ok.
You say you have rebuilt carbs did you use aftermarket kit? I'm wondering if you replaced the float chamber gaskets and they are catching the floats and hanging them up as you are running.
Repaired petcock mmm not got a great success rate take off the vacuume pipe from petcock if there's petrol in the vac line the repair has not worked.
When you put the petcock on prime do the carbs flood if so the float valves are not sealing don't leave it on prime to long as over time you could find you have petrol in your sump contaminating the oil.

[Steve]

... they do not look very buoyant when floating in petrol with only 8 to 12mm sticking out of the petrol.

I don't have an VM floats here to check, but I would think that there should be a bit more than that sticking out.

Remove the floats. Shake them to see if you can feel any liquid inside. If you can, they need to be emptied and re-sealed.

.

[Nessism]

You might want to measure fuel level as detailed in the factory manual. A piece of vinyl tubing "pencil sharpened" at the end will sort of screw into the drain plug hole and seal well enough for the test. Fuel level is the critical specification that must be met, float height is just an approximation to that ends.

[tom203]

I'd be suspicious of the the gasket (or o-ring) under the needle valve seat....if wrong type , the fuel would overflow bowl rather quickly .

[Burque73]

.......A piece of vinyl tubing "pencil sharpened" at the end will sort of screw into the drain plug hole and seal well enough for the test.......

That's simple and brilliant! I've not heard this trick yet, thank you!

[derkiow2]

thanks for the replies , double triple checked all suggestions . I am left with float buoyancy, so if there anyone who could measure or take a pics of one these slider floats bobbing up and down that would be great. It would be great to rule out the buoyancy , the float height had to be increased to by several mm to get the right float bowl fuel level. The carbs where playing up before I overhauled them the only things I did'nt replace where the floats....Thank,s

[Nessism]

If you verified fuel level then float buoyancy is immaterial. All that matters if the fuel level in the bowl, not whether or not the float is heavy and sinking a little.

[derkiow2]

Thank you for your reply. My thinking is, the buoyancy of the floats has diminished and there is only enough upward force to close the needle valve whilst stationary. Any movement ie bump in the road and the floats can't keep the needle valves closed and Or, maybe the specific gravity of the fuel has altered. I'll take some pictures of my floating in petrol , maybe someone could compare or tell me what they think.

[Nessism]

Please also take some photos of the fuel level using the clear tube method so we can see how you performed the test.

[derkiow2]

Just let everyone who replied to my message . The problem is now solved I bought four new carb floats of a friend . The float height setting is now right for fuel level in the bowl. The new floats are more buoyant than the old ones.

[Gorminrider]

good man! Have you got a theory for what happened to the old ones to make them heavier? Or were they different in appearance?

[Nessism]

I still say if the floats were heavier they would sink further into the fuel and the fuel level would be high. The clear tube test would bear this out.