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Old Feb 17, 2012, 10:59 PM
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Andersoneric04's Avatar
United States, WI, Madison
Joined Feb 2012
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tuning low end needle

Hi guys I recently bought a Super Tigre 51 ringed airplane engine. I have slowly leaned my high speed needle through a half a gallon of 18% oil / 10% nitro. It's currently about 5 clicks rich from max speed. Now I'm in the process of tuning the low speed needle because the engine bogs down when "hammering" to WOT. I've slowly leaned the low speed needle a full turn from the factory setting. A full turn seems a bit extreme to me but I'm only familiar with tuning heli engines so I'm asking you guys for help. After leaning the low speed needle a full turn the engine has "decent" response when going from WOT to idle and back to WOT. However, if I let the engine idle for appx 10 seconds and punch it to WOT the engine bogs down so much I'm afraid it could quit. Should I continue to lean the low speed needle? Will this improve as the engine is "broken in?" Will leaning the low speed needle increase the lowest speed the engine can idle at? Thanks in advance for the help. I'm really excited to get this bird in the air!
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Old Feb 18, 2012, 07:15 AM
Registered User
Jacksonville Fla.
Joined Mar 2007
2,214 Posts
I adjust the low end first...some do the high end first...I pinch the line from the needle valve to the carb closed...I'm looking for the engine to continue to run for 3 or 4 seconds then it will rev, (because it is leaning out) and start to die..release the line....adjust the high end to max speed by ear richen it a 1/8 th of a turn or so....let ti cool and re check the low end....now let it idle for a couple of minutes and advance the throttle...don't slam it up but advance it within 2 seconds...it should advance without stumbling.....if it loads up and ..bogs the lean the low end....if it stumbles like it isn't getting fuel richen the low end....
If the motor gets worse after any adjustment put the last adjustment back where it was
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Old Feb 19, 2012, 12:16 AM
TigreJohn
United States, CA, Corona
Joined Aug 2008
996 Posts
Hate to disagree with Jetmech05, but his tuning procedure in total is not the best method.The high speed needs to be set first. The high speed needle controls to wide open throttle fuel flow to the engine. The low speed needle restricts the fuel flow at mid-range and idle where less fuel is needed.

Take a look at the "...set/tune your engine" at the top of this forum for this forum for good advice.
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Old Feb 19, 2012, 10:46 AM
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Jacksonville Fla.
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notice I said to recheck the low end after you adjust the high end
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Old Feb 19, 2012, 09:40 PM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
Joined Jan 2005
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It really should make no difference which you do first but I do the high end out of habit. I beleive also....when tuning.. the breakin is done at the upper rpm ranges with cooling between hence beginning with the high speed needle first. But if you have an engine already broken, it shoulidn't matter which you begin adjusting first as they aren' dependent.
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Old Feb 19, 2012, 11:51 PM
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downunder's Avatar
Adelaide, South Australia
Joined Sep 2003
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For Super Tigres, adjust the high speed, adjust the low speed (best done with the pinch test giving a slight rise in revs before quitting) then adjust the mid range if it stumbles on transition. Mid range? Yep, ST carbs have a mid range adjustment by loosening the 2 screws on the side of the carb and rotating the angle of the fuel nipple. Rotating it slightly down richens and vice versa (assuming it still has the factory setting).
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Old Feb 20, 2012, 12:34 PM
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Andersoneric04's Avatar
United States, WI, Madison
Joined Feb 2012
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Quote:
Originally Posted by downunder View Post
For Super Tigres, adjust the high speed, adjust the low speed (best done with the pinch test giving a slight rise in revs before quitting) then adjust the mid range if it stumbles on transition. Mid range? Yep, ST carbs have a mid range adjustment by loosening the 2 screws on the side of the carb and rotating the angle of the fuel nipple. Rotating it slightly down richens and vice versa (assuming it still has the factory setting).
Thanks for the great insite. I leaned the low speed another half a turn and it runs great
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