tale spin

I'm running a Super Tiger 90 on an edge 540. I bench ran the engine as specifide by the manual. It ran like a champ. I mounted it on the plane and went to the field to fly. Started up and idled fine and ran fine. took to the air and flew for a few minutes, throttle back to half engined loaded up and tried to die on throttle up. got back to mother earth.
reset carb and idle screw. ran fine on ground went back in the air same results. ran on ground at idle would load up. reset idle screw and main jet still same results. checked engine for leaks and also carb and fuel tank all was tight. Has anyone had this problem going rich in the air?

SPLIT S

I don't know how this may apply to you but while I was running in my S.T. G51 the high speed needle started moving on it's own. Careful inspection showed that one side of the spring steel that the knurled part of the needle rides against wasn't making full contact with the needle. Vibration was causing the needle to rotate counter clockwise causing the engine to richen. I removed the needle and adjusted the spring steel - engine holds it's setting fine now.

Hope this may help,
Dan

Dave McDonald

My Feedback: (19)

Both of my ST 90 engines had the same problem. They run fine at idle and wide open, but tend to load up rich at half throttle. No amount of tweaking with the carb was able to cure the problem. Even tried an OS 7D carb with no improvement.

waynem

My Feedback: (58)

The super tiger 90 has an ajustment with the carb. center that rotates. Loosen the two screws that hold on the side of the carb. and rotate. I dont know which way to turn the center but, it adjusts the mid-range.It takes very small movement. Wayne M.

Dave McDonald

My Feedback: (19)

Yep, tried all that too, but it didn't cure the problem.

joey_snaproll

My Feedback: (32)

Maybe try a hotter glow plug. if you switched carbs it has to be somthing else.I run a os f four stoke plug in my TT120 and works great.
I have a few ST 90's and they run great.I know I changed those glow plugs too.The one thing I had to do with one was to put a little loctite on the low end screw setting it was very loose too loose and I could see that viberating out.After I put the loctite on let it dry and turn the screw to free it ,the setting stayed put .

Joe

Deadeye

I have a ST 75 that has the same problem. Piece of junk carb. I use mine as a paper weight, and a reminder to NEVER buy another Super Tigre.

Ed_Moorman

My Feedback: (1)

What is the diameter of the carb base that fits down inside of the crankcase?

The reason I ask is I had the same thing happen with a Tower .75 I bought. I tried a carb from one of the SK 90s I have and it fit perfectly and it cured the lean mid range. I ordered a new SK90 carb for $29 and it, too, works like a charm. This has only been on the bench, but I have run the engine at several different mid range carb openings-varied a few clicks-for a timed 60 seconds, then popped it to full power and no hesitation, no loading up. It will idle for 60 seconds, then snap to full power at that low end setting, too.

I did have to shorten the base of the SK carb a little. The Tower carb is 1/16 shorter. It does have 2 O-rings, one is down in the crankcase opening so it sealed for the test run. After I received the new SK carb, held it up to a sanding disk and shortened it 1/16" Fits perfect, now, and seems to run perfect, too. In the photo, the SK carb on the lower right is off one of my .91s. Note the shiny base is longer than the Tower carb. The SK carb on the left was the one I ordered and has the base sanded down to match the length of the Tower carb.

The SK & Tower base is .59 or 15mm. I also checked an old ST carb I have and it is 15mm. I can't say what the Chinese ST carb base diameters are, but I would suspect they are the same.

[link=http://www.kangkeusa.com/skengines.htm]SK Web site[/link]

I think the ST carb I have it one from an old ST 2500 or 3000. These engines came with a crab from the 90, as I recall, and used a split sleeve to size the crankcase down to fit. I, and a lot of other early giant fliers, used to use OS 7D or ASP 1.08 carbs on all my big Tigres, so changing the carb out on an ST is not new.

flapper

Hi, had the same problem with my G90 where it would just start to run excessively rich after a few minutes. I found the inner thread on the high speed needle had stripped and would just pull off the threaded part on the needle valve assembly. It appears the needle valve was moving out.

I have no idea why the thread would strip the way it did. Vibration maybe? I purchased a new needle valve assembly and is working great. I had about 100 plus flights on the engine (same plane!) but would never have thought I would have this problem.

Try winding the high speed needle valve out a bit and see if it will just pull off over the threaded part. You may have the same problem.