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Old Oct 25, 2012, 06:27 PM
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RC_Feen's Avatar
Culpeper, VA
Joined Oct 2005
692 Posts
It's running!

Well got the OS GT33 fired up for the first time. Took awhile but finally got it running. Challenge now is getting these end points set. Burned a complete tank of fuel messing with the end points and still don't have it right. I have the needles set to default two turns out for L & H for rich settings. Running 25:1 now for the first gallon. A lot of oil coming out onto the ground or should I say I left a big black spot in the yard that I had to wash away with some soap and water. At WOT it's taching at 5500rpm. Is this normal for break-in running 25:1 ratio? Going to try tomorrow to work on the end points again and maybe get it in the air. Really don't want to try to maiden until I get the end points set right. As far as the throttle curve...I witched back over to AERO model on the Dx7 rather setting it up using HELI mode. Not sure if setting up the Tx for the airplane using Heli mode is possible or if I'm missing something with the throttle curve in AREO mode on the Dx7. Any feedback, pointers or tips would be helpful. I'm going to find out if I can get someone from our local club that has more experience setting up a gasser that could maybe help me out tomorrow or Saturday. Thanks!
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Old Oct 25, 2012, 06:51 PM
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winston mo
Joined Oct 2006
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Don't do it. There are no default settings. Tune that motor.
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Old Oct 25, 2012, 06:55 PM
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winston mo
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You also won't have to have a curve on your throttle if you have your servo arm pointed 1 position ahead of the 180 degree mark. The arm should be pointing off the narrow side of the servo with the throttle closed or close to it.
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Old Oct 25, 2012, 06:57 PM
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USA, TX, Spring
Joined Jan 2008
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Mine would not even start on 2 turns out. Thanks to racerman27410 I turned down both needles and ended up at 1 1/4 turns to get it to start and then continued tuning with the tach and then went by ear. At 2 turns out I flipped that prop 300 times and it never even sputtered....yea I dont know when to quit. Then I got on line for some help. I was going by the manual at the 2 turns but that is set for all altitudes etc. Mine does not leave a mess on the ground and I'm running at 25:1
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Old Oct 25, 2012, 07:15 PM
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Culpeper, VA
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Quote:
Originally Posted by kerwin50 View Post
You also won't have to have a curve on your throttle if you have your servo arm pointed 1 position ahead of the 180 degree mark. The arm should be pointing off the narrow side of the servo with the throttle closed or close to it.
Picture would be 100% helpful. Right now I have my throttle sub-trim at 0 and my throttle end points at L=100%, H=100%. I keep changing my throttle servo arm angle but not sure if my linkage is too long or too short to get the correct geometry. I could post a pic what my current setup looks like if that would help?

Quote:
Originally Posted by going4speed View Post
Mine would not even start on 2 turns out. Thanks to racerman27410 I turned down both needles and ended up at 1 1/4 turns to get it to start and then continued tuning with the tach and then went by ear. At 2 turns out I flipped that prop 300 times and it never even sputtered....yea I dont know when to quit. Then I got on line for some help. I was going by the manual at the 2 turns but that is set for all altitudes etc. Mine does not leave a mess on the ground and I'm running at 25:1
I hear yeah! I spun that prop this afternoon so many times I had beads of sweat rolling of my forehead. Would have thought I just jumped out of the pool. I'll re-set the needles tomorrow to 1 1/4 out and re-tach it.
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Old Oct 25, 2012, 07:20 PM
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winston mo
Joined Oct 2006
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I'll try an post a pic or find the diagram.
Your end points are fine for now it's your linkage that is probally what will need to be changed.
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Old Oct 25, 2012, 08:36 PM
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Culpeper, VA
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Originally Posted by kerwin50 View Post
I'll try an post a pic or find the diagram.
Your end points are fine for now it's your linkage that is probally what will need to be changed.
Thanks! If you have a measurement of your throttle linkage from end to end that might be a good start for me but each setup might be different!
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Old Oct 25, 2012, 08:54 PM
The Twisted Elf
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USA, NJ, Trenton
Joined Nov 2010
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Originally Posted by RC_Feen View Post
Okay cool! I have the piece on the belly with the v-slate pieces cut for ventilation and also were my vent line for the gas tank comes out. Like this:

that will work just great ,
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Old Oct 25, 2012, 09:20 PM
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Culpeper, VA
Joined Oct 2005
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Gas oil ratio

Well I think I may have found out why my OS GT33 was running so rich other than my 2 out from close L&H needle settings. So I mixed 1 8oz Lawnboy 2-cycle oil to 1 gallon of gas. Yeah....that equals 16:1 ratio! Not the 25:1 I wanted. No wounder I had a huge black oil spot on the yard from the exhaust! So I think I need to add another 1/2 gallon of my 93 octane non-ethanol gas to my mix and I should be at the 25:1 ratio I was intending to be at.
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Old Oct 25, 2012, 10:43 PM
3d NOOBular
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USA, UT, St George
Joined Aug 2010
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Quote:
Originally Posted by RC_Feen View Post
Well got the OS GT33 fired up for the first time. Took awhile but finally got it running. Challenge now is getting these end points set. Burned a complete tank of fuel messing with the end points and still don't have it right. I have the needles set to default two turns out for L & H for rich settings. Running 25:1 now for the first gallon. A lot of oil coming out onto the ground or should I say I left a big black spot in the yard that I had to wash away with some soap and water. At WOT it's taching at 5500rpm. Is this normal for break-in running 25:1 ratio? Going to try tomorrow to work on the end points again and maybe get it in the air. Really don't want to try to maiden until I get the end points set right. As far as the throttle curve...I witched back over to AERO model on the Dx7 rather setting it up using HELI mode. Not sure if setting up the Tx for the airplane using Heli mode is possible or if I'm missing something with the throttle curve in AREO mode on the Dx7. Any feedback, pointers or tips would be helpful. I'm going to find out if I can get someone from our local club that has more experience setting up a gasser that could maybe help me out tomorrow or Saturday. Thanks!
What prop are you running on that thing? 5500 rpms sounds pretty weak even on a really oil-rich mixture. I think you are SUPER rich and going to build up a ton of carbon on the top of your piston and you are going to foul your spark plug. If you pull it out now it probably already is. I'm guessing when it is tuned properly you are going to see numbers around 7000-8500 rpms on an 18x8 prop. I'm guessing more toward the 8500 number than the 7000. You may also not be opening the throttle all the way I guess. Hope this helps.
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Old Oct 25, 2012, 10:59 PM
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Culpeper, VA
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Originally Posted by brathanke View Post
What prop are you running on that thing? 5500 rpms sounds pretty weak even on a really oil-rich mixture. I think you are SUPER rich and going to build up a ton of carbon on the top of your piston and you are going to foul your spark plug. If you pull it out now it probably already is. I'm guessing when it is tuned properly you are going to see numbers around 7000-8500 rpms on an 18x8 prop. I'm guessing more toward the 8500 number than the 7000. You may also not be opening the throttle all the way I guess. Hope this helps.

Running the 18x8 break-in prop and the throttle is hitting the mechanical end stop unless when I put the new carb arm I didn't put it on right to where I would get the max opening/throw.
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Old Oct 25, 2012, 11:35 PM
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USA, UT, St George
Joined Aug 2010
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I can't imagine it only turning 5500 rpms at full throttle... how is the throttle response? You should be getting really fast throttle response as well as a lot more rpms. I think it's just a tuning issue. That engine should pull like a freaking little mule.
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Old Oct 25, 2012, 11:42 PM
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United States, NC, Greensboro
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Hard to believe you even got it running with the needles that far out and that much oil in the gas.
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Old Oct 26, 2012, 12:05 AM
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Culpeper, VA
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Originally Posted by racerman27410 View Post
Hard to believe you even got it running with the needles that far out and that much oil in the gas.
I can't even tell you! A lot of throttle trim..sub trim..re-positioning throttle servo arm. I was all over just trying to get it to fire. As soon as I finally got the gas to the carb and the first spark I was back and forth....First gasser learning experience I guess. Still learning and if was easy why would we do it?
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Old Oct 26, 2012, 01:20 AM
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United States, NC, Greensboro
Joined Dec 2006
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Originally Posted by RC_Feen View Post
I can't even tell you! A lot of throttle trim..sub trim..re-positioning throttle servo arm. I was all over just trying to get it to fire. As soon as I finally got the gas to the carb and the first spark I was back and forth....First gasser learning experience I guess. Still learning and if was easy why would we do it?
well at least you are getting your starting arm in shape!
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