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TOPIC: Weeping Carb Float Bowls KZ750B-4

Weeping Carb Float Bowls KZ750B-4 02 Jul 2020 23:52 #829671

  • kz_kon
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Hi folks,

I've just finished rebuilding a 1979 KZ750B-4 twin. I've completely rebuilt the carbs (o-rings, gaskets, jets, needles and seats, etc.), including new OEM float bowl gaskets.
I've snugged down the float bowls as they should be, yet I consistently get some fuel weeping out of the #2 float bowl. It looks like it's coming from one of the corners where the screw hole is.

When I remove the bowls, you can see that the gaskets are seating because witness marks are left around the perimeter of the gaskets. If I tighten the bowls down any more I will strip out the threads on the carb bodies.

The lip of the bowls, and of the bodies are flat.

One thing I've noticed is that when I fit the bowls onto the carb bodies without the gaskets (to see fitment), the emulsifier tubes which slide into the float bowls, just above the main jets (the main jets are installed in the bowls)bottom out on a shoulder in the bowls, so the bowls don't sit flat onto the carb bodies without the gasket in place. They leave a small gap. The gap is smaller than the gasket thickness, but there still is a gap.

I have tapped the emulsifier tubes into place so that they are well seated (they also both have new o-rings). Still, there is play between the float bowls and carb bodies.

I have a spare set of '79 carbs and they do the same thing, so this seems to be a feature of these carbs, and not a quirk. In all of my years of building and working on bikes, I've never encountered this before.

So, does anyone have any firsthand information regarding carbs for a KZ twin? Do you have similar issues? If so, how did you solve it?
I am considering doubling up on the gaskets, but I shouldn't have to, so I want to see if there's something I'm missing.

Thanks, in advance.
Current bike: 1979 KZ750B-4
Past bikes: 1976 KZ900A-4 (I sure do miss this one)/ 1975 Z1 900 motor in an AmEn Savior frame (I sure do miss this one, too!)/ KZ440 with belt drive (I don't remember the year)/KZ650 (I also don't remember the year for this one).

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