Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

Nelson 40 ss air leak?

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Old 01-03-2010, 06:44 PM
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ecoliburger
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Default Nelson 40 ss air leak?

Tried to get my Nelson running today. Had to open the needle about 6 turns to get it to run and then it was not really that rich. Figure I must have an air leak or something obvious I am overlooking. Any suggestions? Pressure checked the tank and all the fuel lines which are new, no problems there. I am running one of those needle valves with the nipple on the same side.
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Old 01-03-2010, 08:25 PM
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racerxwest
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Default RE: Nelson 40 ss air leak?

Try cleaning the spray bar and or the fuel filter. Also makw sure the spry bar lines up with the hole in the air valve.
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Old 01-04-2010, 12:02 AM
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Default RE: Nelson 40 ss air leak?

Any trick to lining up the hole in the spray bar?
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Old 01-04-2010, 12:34 AM
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GREG DOE
 
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Default RE: Nelson 40 ss air leak?

You need to take the spray bar out and clean it. If you don't want to do that, at least remove the needle
valve and pump fuel through the spray bar. Than plug the needle valve hole and pump fuel again, and
observe if a steady stream of fuel is comming out of the hole in the carburetor or venturi. If you feel resistance there is a good chance the spray bar is turned so that the hole in the spray bar is no longer
lined up with the hole in the venturi. My engines are older, so I don't know if there have been design
changes. If this hint applies to your engine, you will know from my description what to do.
Here's the tip: every Nelson spray bar that I've ever see has the hole exactely lined up with one of the 6
points on the wrench "hex". Mark that hex and reinstall the spray bar making sure that the "hex" point
is pointed directly into the matching venturi hole. Good Luck, Greg
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Old 01-04-2010, 10:40 AM
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Bill Vargas
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Default RE: Nelson 40 ss air leak?

You may also have a worn out head.

With the glow plug installed, squirt some after run oil around it,,,, turn the prop thru compression and observe for bubbles around the glow plug. If bubbles are present you need a new head.


BV
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Old 01-04-2010, 10:49 AM
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Default RE: Nelson 40 ss air leak?

Thaks guys, I will give your suggestions a try
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