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Lx 90 full pipe singer size

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Old 11-18-2017, 11:59 AM
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SACKRC
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Default Lx 90 full pipe singer size

On my lx 90 have a mac full pipe straight no muffler set at 14 inchs to first band.. stinger size .320 . The stock size was in the .400 range. At this size my back pressure was to low for proper fuel draw.
Engine is on a cermark alley cat. Reduced it to .320 ( which is your muffler size. Engine seems to over heat easily, fuel draw is good now. Using a 11/8 @ 15000 to 15500 rpm
When I'm airborn I set it on a slight rich setting , and after a few laps it will start to lean, but if not the perfect setting it will over heat and go lean.
thanks Rich B.
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Old 11-19-2017, 05:39 AM
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Are you launching it 1,000rpm rich of peak? These engines will not tolerate the sport engine mantra of "slightly rich".
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Old 11-19-2017, 07:26 PM
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Not sure, usually check max rpm and set rich by ear , have to check with tach thanks What about my stinger size?
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Old 11-20-2017, 08:44 AM
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Originally Posted by SACKRC View Post
Not sure, usually check max rpm and set rich by ear , have to check with tach thanks What about my stinger size?
I can't help with the stinger size as I've not had a .90, but my 56LX has a 7.5cc tuned pipe (ordered from Dub with the pipe) and the stinger has a small bushing pressed in to reduce the ID by about .030" or so. This is just a guess as I'm not home to measure it.

As for setting the needle - I suggest watching Dub's tuning videos on YouTube on how to find peak and set the needle valve on his engines. These engines unload a lot in the air and as such need a fatter needle setting before launch. I was told by Bob Brassel to set the needle for 800-1000rpm off peak for launch. If you don't have a tach, I would start out pretty fat on the needle so the engine runs notably rich and missing every so often and lean it down until it is just barely running clean. Also make sure you're using 15% nitro fuel - using less nitro requires a little less prop load.
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Old 11-20-2017, 06:25 PM
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How do I get Bob , he should have my answer. Thanks for your input. Rich b.
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Old 11-20-2017, 06:27 PM
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How do I get Bob , he should have my answer. Thanks for your input. Rich b.
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Old 11-22-2017, 10:28 AM
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For some reason, he doesn't sometimes get notifications that someone posted here. You could try sending a PM or Email through his profile page or call/email Dub Jett through his website - dubjett.com or I believe jettaerotech.com.
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