Monday, April 11, 2011

Pixies Ate My Carb

Apparently the Supreme Being decided that Chicago had suffered enough of a miserably cold and wet Spring and decided that last weekend should resemble July instead of April. I took advantage of being able to work in the garage, with the door open. I decided that I was going to tear down the carburetor one more time to determine, once and for all, what was 'not right' in there. With the bright sunlight, it was pretty easy to see into passages and small spaces. As usual, I didn't find anything that struck me being wrong or out-of-place.
However, upon closer inspection of the threaded opening for the needle jet, I see that the threads have corroded somehow. I can only assume that there was water in the float bowl, for quite some time, at some point. I don't think that gas turning to varnish would cause aluminum to 'decompose' like that. I'm still not sure how that would cause a lean condition. I would think that if fuel were leaking by the needle jet, it would cause a rich condition. Perhaps air was getting sucked into the needle jet through the corroded threads? It would seem that the air pocket, in the float chamber, would be above the baffle (that tan colored funnel shaped thing). Therefore air couldn't make it past the needle jet. I'd love to chat with a carburetor expert and find out for sure. The (temporary?) resolution seemed to be to wrap the needle jet threads with Teflon tape. I was careful not to cover any holes in the needle jet or leave extra Teflon past the threads. I reassembled the carb, re-installed it and warmed the engine. Clearly, the fuel/air screw was out of adjustment because the motor would barely idle. So, I took it for a short spin because it would run better at higher rpm. After warming the engine and adjusting the fuel/air mixture (+ 1/4 turn - the fuel/air mixture screw is at the bottom of the picture), I went for a ride. It runs better, noticeably better. It pulls in all gears and the hesitation is gone. Additionally, I can run without any choke and it still runs well. On the ride to work this morning, it felt the same. I even noticed myself 'short shifting' into a higher gear instead of having to spin the motor like mad to keep up with traffic. It was actually fun not having to worry about someone behind you running you over (because you're too slow). What concerns me now is if the Teflon will 'hold', that is will it be a solution or just a temporary fix? I've already started searching for used NX carburetors, just in case.

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