Clear tube test air problem...

Dear kz fanatics,

I'm trying to check the float fuel level in each bowl via the clear tube test ... the problem is when i open the drain screw on my Mikuni BS34 i have a big air pocket inside the tube which i can' t get rid of.... this give me misreading every time...

What do you do in this case... seems nobody had this problem before (it's not posted in the forum yet)?


regards,
laurent

I am not quite sure how there could be a air pocket in the tube. Usually a tap on the tube will dislodge any air in it.

This don't work but maybe because I've got air in the bowls ? They were previously all cleaned thus dry inside.


regards,
laurent

The fuel should push the air out in front of it and at worst have a few bubbles in the tube. I agree with Otakar, I don't see how a large pocket could form as the surface tension of the fuel should push the air out in front of it.

fluid will push air out unless you have the tube blocked which would would trap air, basic physical science there

ELCouz wrote:

...trying to check the float fuel level in each bowl via the clear tube test ... the problem is when i open the drain screw on my Mikuni BS34 i have a big air pocket inside the tube which i can' t get rid of.... this give me misreading every time...What do you do in this case... seems nobody had this problem before (it's not posted in the forum yet)?....

Assure bowl vent hose is clear, exits to open air, and isn't kinked or blocked.

Could start test with already drained (dry) float bowl;
then set everything up with loosened drain screw;
last thing being turn petcock to PRI.

As fuel flows into float bowl, fuel should simultaneously flow into the clear tube.

Air inside bowl should be displaced by incoming fuel, and exit through the vent.

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If bubble in test line persists, try starting test with full float bowl;
turn petcock to ON (non-flow position);
attach and hold clear tube in position;
loosen drain screw;
turn petcock to PRI.

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If bubble in test line still persists, try starting test with full float bowl;
turn petcock to ON (non-flow position);
attach and hold clear tube in position;
turn petcock to PRI;
loosen drain screw.

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Good Fortune!

Yeah, sometimes you get air in there, and it does alter the level. Usually you just play with it a little and the buble should come out.

You should have a pan umderneath to catch gasoline. I usually let some run out of the tube and then lift the tube while it is running. This usually gets the air out for me.

The air bubble isn't an issue with manual slide Mikuni having side located or bottom located drain screw, where screw is removed and fuel flows through drain hole into the clear tube.

Am guessing there's sometimes an air bubble problem when dealing with CV carbs that have dual purpose nipple at bottom of bowl (normally overflow that also serves as drain when screw is loosened).

Good Fortune!

Yeah, sometimes you get air in there, and it does alter the level. Usually you just play with it a little and the buble should come out.

You should have a pan umderneath to catch gasoline. I usually let some run out of the tube and then lift the tube while it is running. This usually gets the air out for me.

Yes, i've changed my clear tubing for a more flexible one... i was able to play with the pocket back and forth, finally i've got them.

thank you guys, it worked!

regards,
laurent

Glad it worked!

Patton, yes, the ones that seem to get an air bubble are the ones that have the dual purpose drain/overflow. But it's not a real big problem..just have to play with it a little.