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Stromberg Carb

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bob turner

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I am pretty good at these - set mine up in the 1990s and it hasn’t faltered or leaked.

The New Cub (not new any more; we have had it for 11 years and 1100 hours) has always leaked a bit. We just turn the fuel off when we park overnight. But it got worse, causing a rich mixture at idle, so time to take a look.

I put it on the calibration stand, and it sealed at 13/32, right on the money. Cleaned the passages, assembled, tested. Ok for about five minutes, then black smoke.

Off again - this time I planned to do my ten trial thing with the float. You know, if it fails to seal just once in ten trials, back to the bench. By golly, it failed at the sixth trial.

Lapped the needle - same deal. Failed at trial #6. Did it again - ditto.

So this morning I changed the float. What else could affect it after five successes?

Not the float! But I had a brand new seat in an envelope from Kelly AFB, so why not? At my wit’s end.

Before I installed the new seat I had a good look at the old one. Ten-power, and in sunlight. But I really didn’t need all that - it was obvious that someone had installed a seat designed for a Neoprene needle! And the needle was stainless.

It took five tries to get the float level back to13/32, and then I did my obligatory ten trials. Perfect. Fifteen successes in a row - no leakee! Tomorrow I test-fly.

I swear - I have seen it all with Strombergs! The notches in the needles can be rough. Floats can leak! Folks can install the wrong parts. What’s next? Good thing I am retired, and not charging a customer for all this effort.
 

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