Super tigre carburator adjustment
06-22-2016, 04:28 PM
#1
Super tigre carburator adjustment
A friend of mine gave me his Super tigre 60 to get running after sitting up for a number of years. After a through cleaning it started right up. With the carb set to high idle it seemed to run just fine. After a little warm up I moved the throttle to wide openand the engine respounded and was screaming. Aquick throttle down and the idle was again satisfactory. Here is the problem !!!. Adjusting the needle valve has no effect on the engine speed. I even screwed the needle out all the way and as fuel ran out the end where the needle valve was it still ran at top speed.( lean condition). Nothing I could do would richen the engine. At first I thought it was a gummed up carb. But a second cleaning and double checking the tubes confirmed no blockages. I thought about just leaving it as is because it would run fast and idle good. As I transitioned from idle to high speed I noticed that the mid range was so lean that the engine would lean out and die. After checking out the low idle screw and re adjusting I could get it to idle again and noticed that the high end was now richer. This got me to thinking that the problem was in the correct correlation between the low speed needle and the high speed needle. After several tanks of gas and adjusting and re adjusting both needles I can now get the engine to run rich and the high speed needle works just fine as well as the Idle. THE DARN ENGINE STILL LEANS OUT AND DIES AT MIS RANGE.Help, any suggestions.John Castronover
06-22-2016, 06:18 PM
#2
Where is the discharge orifice (commonly called the "cats eye" aimed in the carb currently? It should be straight in (facing the crankshaft when installed). When adjusted either way from straight in, it typically means the fuel mixture in the midrange. A beautiful feature of those wonderful ST carbs. I love them very much.
06-23-2016, 10:29 AM
#3
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J, deliberately set the LS needle rich , then set the HS needle about 200 rpm rich from peak, now set up the LS needle for best transition and idle If the LS needle is too lean it will make the HS needle unresponsive. Always favor the transition over a few idle rpm.
06-23-2016, 11:01 AM
#4
The way I set ST Carburetors is to set the LS needle for a low reliable idle - less than 3,000rpm is ideal. Set the HS needle to your desired setting, and check throttle operation. If the midrange is rich, adjust the spraybar angle in small increments until the midrange is satisfactory. Usually you will have to readjust the needles between adjustments as the spraybar orientation affects the influence of both needles. This is how Pé Reivers taught me to do it.
I don't recall off hand what the initial setting of the HS needle is (3-4 turns out sounds about right though), but the LS needles initial setting should be set less than half way across the cats eye as viewed from the bottom of the carb with the throttle barrel fully open.
I'm not trying to step on your toes, Dave.
I don't recall off hand what the initial setting of the HS needle is (3-4 turns out sounds about right though), but the LS needles initial setting should be set less than half way across the cats eye as viewed from the bottom of the carb with the throttle barrel fully open.
I'm not trying to step on your toes, Dave.
06-23-2016, 11:21 AM
#5
If I could ad to the good advise above. The fuel nipple should be pointed at the front motor mount bolt hole for the slit to be aimed correctly. Secondly, you did not mention prop. 11x7 or 12x6 is what is used most of the time. The other thing I would check is the O ring between the carb and block. You could have a leak there. If you still cant get it there are many ST60/75&90s out there. Used carbs are cheap.
David
David
06-23-2016, 12:55 PM
#6
If I could ad to the good advise above. The fuel nipple should be pointed at the front motor mount bolt hole for the slit to be aimed correctly. Secondly, you did not mention prop. 11x7 or 12x6 is what is used most of the time. The other thing I would check is the O ring between the carb and block. You could have a leak there. If you still cant get it there are many ST60/75&90s out there. Used carbs are cheap.
David
David
Again, not trying to step on toes here.
06-23-2016, 02:27 PM
#8
06-23-2016, 03:09 PM
#10
My flying has changed so much since I had a bunch of Tigre's. Back then we would turn and burn with a sport plane or warbird for 8 minutes and then land. Midrange did not mean a lot. Now I am hardly ever full throttle. The good ol days were much easier :-)
David
David
06-23-2016, 03:12 PM
#11
. One of these days I'll get back down to the flying field and fly some 1/2a stuff. 25,000rpm that's kinda slow. Haha.
06-23-2016, 04:58 PM
#12
The default position is with the fuel nipple pointing towards the rear mount hole. The ST instructions say that rotating the nipple towards the front mount hole will richen the mid range mixture by bringing the slit in the spray bar towards the front.
06-23-2016, 05:26 PM
#13
So the moral of the post is - pull the carb off and look through the bottom to see where the spraybar is and for that matter where the idle needle is set. The OP may as well start at square one and "reboot".
Last edited by 1QwkSport2.5r; 06-23-2016 at 05:29 PM.
06-27-2016, 05:09 AM
#15
For the car guys, airplanes are the dark side. For the airplane guys, cars are the dark side. I guess I'm the black horse of the forum..?
06-27-2016, 07:36 AM
#17
My Feedback: (11)
Here's the advice we've been giving for years about ST carbs:
To properly set up your carburetor, there are a few steps...
Make sure the spraybar is set so that the fuel slot is pointed straight down the center of the carburetor. You will have to look through the carb from the bottom, with the venturi opened to full. Loosen the two screws next to the high-speed needle valve to rotate the spraybar so that the slot is centered.The idle needle can be seen in the slot of the spraybar. It looks like a piece of wire that has the end squarely cutoff. It should be less than one-half way across the slot when the venturi is opened to full. The high-speed needle should be opened about 2-1/2 to 3 turns out from closed. All of these settings are very rich. You'll have to start the engine at about 1/4 to1/3 throttle.
Once the engine starts, advance the throttle to full. You can then lean the high-speed needle until the engine is running just rich of peak RPM. When you have the high-speed needle set, you can retard the throttle a bit and use the idle needle to adjust the engine. Retard a bit, and adjust. Keep doing this until you have reached the desired idle RPM and mixture. Remember, since we started out with an intentionally-rich setting, the idle mixture will have to be leaned.
Finally, the midrange can be adjusted by rotating the spraybar a hair. Just loosen the two screws next to the high-speed needle and rotate the spraybar just a tiny bit. Either direction is OK. This will help you get a good transition and midrange.
To properly set up your carburetor, there are a few steps...
Make sure the spraybar is set so that the fuel slot is pointed straight down the center of the carburetor. You will have to look through the carb from the bottom, with the venturi opened to full. Loosen the two screws next to the high-speed needle valve to rotate the spraybar so that the slot is centered.The idle needle can be seen in the slot of the spraybar. It looks like a piece of wire that has the end squarely cutoff. It should be less than one-half way across the slot when the venturi is opened to full. The high-speed needle should be opened about 2-1/2 to 3 turns out from closed. All of these settings are very rich. You'll have to start the engine at about 1/4 to1/3 throttle.
Once the engine starts, advance the throttle to full. You can then lean the high-speed needle until the engine is running just rich of peak RPM. When you have the high-speed needle set, you can retard the throttle a bit and use the idle needle to adjust the engine. Retard a bit, and adjust. Keep doing this until you have reached the desired idle RPM and mixture. Remember, since we started out with an intentionally-rich setting, the idle mixture will have to be leaned.
Finally, the midrange can be adjusted by rotating the spraybar a hair. Just loosen the two screws next to the high-speed needle and rotate the spraybar just a tiny bit. Either direction is OK. This will help you get a good transition and midrange.
06-27-2016, 07:37 AM
#18
06-27-2016, 11:17 AM
#19
Senior Member
Even the car guys separate themselves into glow versus electric , then at my flying club they separate into glow, gas, electric and heli. But we are all in this together and I myself aint predjerduuce .
06-27-2016, 12:04 PM
#20
