Have you checked your Emulsion Tubes?

[Neunelfer]

Here's what we found on a couple of F3's while fine tuning the 914-6/GT. Crushed tubes.

We initially thought someone cranked down on the air correction jets but a quick call to Paul Abbott confirmed that the tubes are plenty deep. Then we ran some digital calipers down the bores... all perfect. All I can think of is; these were damaged in the manufacturing process when they stamped the 3 on the end.

Some of our undamaged tubes were stamped on the sides. These were stamped on the end... might be worth checking. FYI, this was "very" hard to notice as these are small at about 3/16" at the base. I had to use a special lense on my iPhone to capture the detail. I only noticed it while trying to find the numbers with a large magnifying glass.

[1QuickS]

I've seen the end-stamped tubes and there isn't an issue from that. These were hammered to squish them down, I doubt that tightening the air screw would do that and besides, the perpetrator would have needed to put a rod down inside to push against. I think they were hammered to close the holes up, this would effectively increase top end mixture to be richer...easier to solder them shut unless you were short on solder at a speed event and were being resourceful...

[Neunelfer]

What an odd thing... only two out of 6 so, they must have gotten mixed up in a batch at one time. Thanks Paul...

[Frank Beck]

I've heard of pinched fallopian tubes but never this.

So... what were the symptoms? High speed bobble?

[chris_seven]

I have never seen a Weber manufactured tube stamped on the end they are always marked on the sides.

Could it be aftermarket?

[Neunelfer]

Mine are a mixture of both. Only the end marked ones have the issue and only two out of three of them.