I never thought about leakage around the throttle barrel. I wonder if a light coating of epoxy inside the part where the throttle moves would cure it. You'd have to wiggle the throttle back in there, but once you did and worked it a bit so it moves smoothly it would be sealed fairly well. Maybe that's also why my old dirty engines with all the brown castor residue run so well. They are sealed up from air leaks!

Anything that would permit the rubber boot seal to do it's job will certainly help.

I'm wary about applying epoxy to this area though, and the center part of the seal contacts the rotating part of the drum that affixes to the throttle lever.

It may well be that the engines I have that do not exhibit any problems have a better boot seal, though in some cases I've tried swapping in brand new carbs to see if there is any improvement.

Dunno... but it seems like there is something ST is missing in it's design to eliminate the low/mid problem altogether.

The "half moon" fix works like a champ on several aflicted engines I have.... but I know all I'm doing is leaning out an overly rich low end, favoring better transitions.

I didn't mean putting anything on the boot. I meant inside the carb body to tighten up the fit between the throttle and the body. Even if it makes the throttle a little draggy, any standard servo can still move it. Just an idea though.

I have a super tigre 45 and having been wanting to buy a different manufacturer's carb for this engine. Please provide the details on the Perry carb. I have had 3 of the ST engines over a long period of time and have finally determined that they all are built the same and with the same problems. The money saved in buying one of these engines is quickly lost in frustration (I am a dead stick expert because of this engine). Hopefully,  the other carb is at a reasonable price. After much time of tinkering with this engine by myself and a few experts, it is beginning to become a reliable engine but it still does not idle right. I now tolerate a high idle and kill the engine by squeezing the fuel line. The high idle has occasionally caused me problems getting the plane to slow down enough for a good landing....Thanks

The Perrys have been around for a long time. They are known for being very user friendly, easy to tune and consistent. One will set you back around $40.

That said, I've owned two Super Tigres and once they were broken in, they gave me no trouble. As long as there is no air leakage I can get a reliable idle with my G90 around 2500 rpm (slow enough to not pull the plane) and good throttle transition.

I'm assuming the following:

- You've extensively checked for leaks and replaced the fuel tubing.
- You have your clunk 1/4" off the back of the tank or MORE
- There are no fuel flow obstructions and you've tested flow
- Your pressure nipple is clear and the tank is hooked up correctly.
- Your mid range transitions are now good as well as your high end.

Given that, I would suggest you employ the "fix" that I mentioned in a prior post above, showing the "half moon" cutout...

This is easy to do.

You've richened the low end to get a good midrange, but this over richens the low end causing the engine to bog down at times on the ground ( requiring a higher idle to keep running! ) and it will produce deadsticks in the air.

Filing out the half moon will lean the extreme low end solving the LS problem.

You need to do this...

1. Check to see exactly how many turns you have the LS needle set.
2. Remove the throttle barrel body and clean it.
3. Use a small circular file to start cutting the half moon groove.

The intent is not to have that half moon all the way down the opening. Rather file it at about a 30-45 degree angle opening up only the extreme low end.
Also don't make it too large, you want the barrel to close when the throttle is fully shut ( however note you'll have to re-adjust your end point travel to move the throttle LOWER than before ).

4. Clean and re-insert the barrel frequently to check your progress... making sure NO flakes get into the carb.

5. Re-install and start the engine. Adjust the throttle travel to achieve lower RPM's... the engine may seem to idle still faster than before at your current throttle settings ( if it does you've succeeded! ), so you'll need to set even more low end travel.


If the above fails ( it's much easier that it sounds ) you can always opt for the Perry Carb.


It is a good idea to run up the ST engines before you fly, to allow them to come up to operating temperature.

Once they are up to temp they will idle unbelievably slow for a 2 stroker.

Engines designed for the European market are made to run on no nitro. European fuel has no nitro. The Supertigres were designed in Italy. They shouldn't need more than 5% to run correctly.

Yes, I run mine almost exclusively on 5% w/o any problems.

However no matter the above "fix" was still required on some ST engines.

Though ST was originally of Italian design and manufacture, the Chinese plants took over some time ago and there were many modifications done to the engines.

I doubt that as such they are "designed for the European market" with the Chinese production.

Hobbico/Tower is the biggest seller of these engines and now owns ST AFAIK.

I think that I will try the 5% nitro in my engine...I have used 10% and 15% in the past with best results with 15%. The instruction booklet that came with the engine states that 0% to 15% will work fine. My ST engine is now on a  plane that I don't fly so often anymore and I am now enjoying the OS four strokes engines on my other 2 planes. If I could buy a good carb for $40, I think that I would do it. All of my ST engines have had air leaks around the low speed needle end. The new one that I just bought has a high speed needle that you can turn at will and it has little effect on the performance of the engine and yes I put the tubing over part of the high speed needle adjustment to possibly prevent other air leaks. I am hoping that I can do a google search for where I can buy the Perry carb. Thanks</p>