Blitz fuel tank switch sucks air

[rob love]

I was just rebuilding one of these valves yesterday from the lynx. It was seized rather than scratched, so it turned out OK.

I used only fine steel wool to clean this one out, polishing both the body and the center valve body (spindle) as well. If your scratching is light, you might get away with the steel wool, but if the scratch is heavier, perhaps a very fine lapping compound between the two, turning by hand at first, or using a slow speed drill if necessary.

On assembly I used a very very thin smear of petroleum jelly rather than reassembling it dry. The fuel will either wash away the jelly in which case the fuel will act as lubricant, or the jelly will remain and do it's job.

I also added a new washer under the spring to replace the bent up one and return the spring to it's full pressure. I should find out this week if the valve rebuild is successful.

[Richard Farrant]

I have found instances of this, with two way taps and it does help if you ensure there is a little petrol left in the tank not being used, that way it will not draw air, not likely to draw any fuel from it. Air is easier to draw than fuel.

[zemsi]

Hi Richard

Thanks for the hint. Unfortunately, both tanks are full and it happens despite that.

cu
Chris

[Richard Farrant]

Originally Posted by zemsi

Hi Richard

Thanks for the hint. Unfortunately, both tanks are full and it happens despite that.

cu
Chris

OK Chris,
Then it is drawing air through the spindle then. I was thinking it might be drawing from the unused tank as in instances from experience. as said previously, lap the taper tap in with a fine paste, like used for cleaning alloys, etc. One well known brand is Solvol Autosol.
Richard

[Mike Cecil]

I used valve grinding paste: it comes in various grades from coarse to fine, so start with coarse on a badly scratched spindle, and, as Richard said, lap them together till 'Bearing Blue' leaves no or little sign when the tap is put together and rotated.

I also used a modern rubber 'o' ring when reassembling mine, and it worked OK for years after that. The key seems to be (1) an even, fine fit between the spindle and body and (2) good tension on the spring to keep them tight.

Regards

Mike C

[Ganmain Tony]

Chris, not trying to be condesending...but lap means - to grind (finely) the surfaces between the the feul tap and the body of the fuel tap it sits in.

It makes both surfaces sit evenly against each other thus preventing a fuel leak. As Mike has suggested, valve grind paste should work well.

Doing this should provide a pretty good seal. It may still weep a fraction initially but should "Take up" after a while and stop leaking.

[Richard Farrant]

Originally Posted by Ganmain Tony

Chris, not trying to be condesending...but lap means - to grind (finely) the surfaces between the the feul tap and the body of the fuel tap it sits in.

It makes both surfaces sit evenly against each other thus preventing a fuel leak. As Mike has suggested, valve grind paste should work well.

Good call, Tony. We take these tasks for granted, I mentioned polishing paste, only to finish off or if the fit was not bad enough to require use of a fine valve grinding paste.

[Ganmain Tony]

Originally Posted by Richard Farrant

OK Chris,
Then it is drawing air through the spindle then. I was thinking it might be drawing from the unused tank as in instances from experience. as said previously, lap the taper tap in with a fine paste, like used for cleaning alloys, etc. One well known brand is Solvol Autosol.
Richard

And I should have acknowledged your post as well Rich. I think its fair to say you do do a fair bit more of this kind of stuff than me...