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91hz with #61b carb

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Old 07-18-2017, 07:57 PM
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Default 91hz with #61b carb

I recently removed my mixture control valve (29085510) from the carb. I then removed the second part of the mixture control valve which was held into the carb rotor by the small o ring. Upon assembly, I noticed that the second part of the mixture control valve (with the one small O ring on the end) has a slot machined opposite to the o ring. Does this line up with the opening in the larger part of the mixture control valve (with 2 o rings) ? Also, what position should the throttle be at when you insert the mixture control valve into the bore of the carb housing? Do these parts have to be timed or indexed to one and another? I guess in short, I'm asking what is the procedure for installing the mixture control valve into the side of the carb housing? The first attempt resulted in the throttle lever being too tight to move. I noticed that after I loosened the mixture control valve stopper (27681340) the throttle lever instantly turned normal. I placed the small washer onto the side of the carb housing so it is between the mixture control bracket and the carb so that when you tighten the screw it doesn't crush the control valve by creating a stop by bottoming out. Thanks in advance.
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Old 07-19-2017, 07:20 AM
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The small part that goes inside the mixture control valve should have a slot on one end that will key into the main carburetor rotor. This insures proper alignment when you put things back together.

The insert is put into the carb rotor before you install the rotor into the carb.
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Old 07-19-2017, 07:49 PM
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Ok, thanks Bax. I got it together and it works perfectly now. Any ideas as to why the Engine dies when I stay inverted for 2 or 3 seconds from an inside loop? If I continue on round the engine doesn't die. I already changed all fuel lines, filters and most importantly the clunk lines inside the main and header tanks. Also made sure that they don't hang up on the end of the tank from being too long. Thanks again in advance.
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Old 07-20-2017, 06:50 AM
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It will most certainly be a fuel-feed problem. It cold also be a problem with the airflow if the engine is cowled. You can get "funny" airflow when the attitude of the model changes, and that can cause mixture/fuel-feed problems. You may also need to check to see that the fuel tank isn't too far from the engine. You may also need to make sure that the tank vents properly when inverted and that the fuel pickup stays submerged in fuel when inverted. That's also a common difficulty...if the pickup's not submerged in fuel, the engine will quit from fuel starvation. Lots of things to check and work out.
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Old 07-20-2017, 09:48 PM
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Yes, I also agree that it's leaning out. Since I never had this issue before, I'm thinking that it may be the length/routing of the external fuel lines. Also yes, good point about not ruling out the vent lines. I am determined to find the problem by fixing 1 thing at a time so I know which one of many potentials that it was. Thanks again for your wisdom Bax, it's very much appreciated.
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