My first Kit plane is done and almost ready to fly. What I mean by almost is that I have a slight engine problem. I am using a Super Tigre G75 ringed motor that I salvaged from my crashed Ultra Stick. I disassembled it and inspected all the parts for damage. Finding that everything was good, I reassembled it, coated it with silicone oil, and stored it for a few months while I purchased and flew a trainer. I brought it back into service for my tiger 60. It runs great accept for the irritating habit of sputtering and dying when transitioning from high speed to idle. There is only one location where it idles. If I move the low speed needle even a sixteenth either direction, it will not maintain idle upon restart. If I transition slowly, six to seven seconds, there is no problem. If I transition rapidly, as when at the top of a loop on the down leg, flame-out. Anything below half throttle can cause this reaction. I also need about a minute to warm the engine enough to idle properly. I ran one gallon of Omega 15% through the engine before the crash on the original glow plug. I installed a OS #8 glow plug when bringing it back into service and use the same type fuel. Should I go with a cooler plug? How about one with an idle bar? On-board glow? 30% fuel? A sludge hammer and then a quick trip to the hobby store for a Saito or YS? I really like this engine as it operated without these little psycho makers on the stick, but I am a little frustrated with the maiden coming this weekend.

Update:
I went ahead and flew it anyways and was not disappointed. Ran like a champ until I cut the throttle at the edge of the runway on landing, dead stick. This could get irritating. I also noticed that I had rotated the sprayer bar a little, so I will align it correctly before my next flight, possibly Sunday. Super Tigre states that the sprayer bar adjusts the midrange performance.

Spray bar can be moved off center just a hair either way .. I have a G.90 and it worked for me ... you will have to adjust the midrange screw again after the adjustment...make sure you do the top end first

First, there is no "midrange" screw. There's an idle screw and a HS needle. Set the HS needle first. Then, put a short piece of fuel tubing on the fuel inlet. With the idle needle closed, blow into the tubing while holding the carb throat to your ear. Open the idle screw slowly. When you can JUST hear air blowing through, you'll be within 1/8 turn either way of right.

Are you sure you got it reassembled correctly?

Be SURE the idle bar is where it was, using the screw head marks as a guideline.

Silicone? Outside or inside? Why?

Dr.1

Ah! The Clarence Lee method of resetting the idle. Works everytime.

Good luck.

Cheers,

Chip

Aerosol silicone lubricant as a rust and corrosion prohibitive, everywhere.

I am going to go along with the low end here. I have many different brands of engines and most low end settings are not more than a turn or so out---except my supertigers. All four of them are different size and they all have similar low end settings of around 4ish turns out which I attribute to the altitude.

Use that Blow in the carb method. I do, to get it in the ball park and adjust from their

...Fein,


This may be the cause of your problems.
Residues of silicon oils tend to settle on the glow plug element and create a scale-like appearance.

This masks some of the element's platinum from the fuel's methanol, which prevents it from catalytically reacting with it, to keep it hot. This is the whole basis of glow ignition.


...Driver,


The carburettor that ST engines come with, does offer the possibility to fine-tune the mid-range, by releasing the screws that hold the spray-bar assembly and rotating it slightly.

In most fuel metering carburettors, the low-speed needle (/disk/other) controls the mixture strength, from idle to about 75% throttle. In ST, the spray-bar adds this fine adjustment possibility, for a better tune.

Setting the sprayer bar straight down in relation to the carburetor bore did the trick. It again runs like it did when new. Now, if this thing will finish breaking in, I can fly like it is supposed to.

Take it slow, STs usually take a little longer than other engines to break in.

Dr.1

You can get a lot more out of this engine by removing the baffle in the muffler. Look down the exhaust outlet and you will see the head of a pop rivet. drill it out carefully and you will release a aluminum disk in front of it . The disk is a restrictor that was intended to keep noise down. ( It really keeps power down) You will pick up a lot of RPM's for sure.
The disk can be driven forward to the exaust inlet port where you will get the full picture. Using needle nose pliers you can bend and crimp carefully until removal is accomplished. Avoid scoring the inlet as it must fit the header pipe. This is easy to accomplish, will still provide ample pressure for fuel feed and really does not produce offensive noise.
I have a G-75 and a G-90 that have the treatment.
The G-90 is on my UCD 46 a nice match as the ST's are so light.

I am willing to wait to get this thing broken in correctly, but having to change HS needle settings every few runs because it leans out too much for my taste is a boor. By the way, I am getting 6 3/4 lbs of thrust with a 12x7 prop. At this stage in my modeling and piloting career, enough. I have almost a one to one ratio as it is, with the break in prop. My instructor brought it in to hover and shut up the local 3D'rs who said you couldn't hover well with a Tiger 60, and then pulled 100 mph+ runs down the flight line at ten feet. I like this plane, I like this engine, I love this combo.

P.S.
I soloed months ago, but Bob will always be my instructor. He is the kind that when he speaks, people listen, and everyone has him maiden their plane, even after they already did it a week ago.

Carb issues? Look here. http://www.supertigre.com/faq/product-faq.html#q22

I think that you are experiancing "break-in problems" which would explain the changes in the settings. These engines take a little longer than most to seat the rings and loosen up to run really well. Carb settings are part of that and will eventually settle down, I just had to reset my G-90 as the idle increased beyond the ATV adjust on the transmitter, it has about 3/4 gal thru it so far and is just starting to run really well (have an OS 7m carb on it ) I rather think the carb is really not the problem for your engine if it's not fully run in.
I had a G-51 that took almost 2 gals. before it stabalized, it became a good reliable screamer...