Steven H

I have been pulling my hair out trying to get this g90 running right. Now I'm sure I have the low speed needle way off. It seems to be running ay rich at low speeds and lean at high speeds. I can hear a metal to metal clicking noise at lower speeds and at certain RPM's it seem to be causing the radio system to glitch. I am about ready to pull it out and try something else. I have another older Super Tigre and have had similiar luck with it. What am I missing? Is there some trick to Super Tigre's that don't apply to other engines? Any and all suggestions would be appreciated.

Thanks,

Steve

ThumbSkull

My Feedback: (57)

Sell the ST, buy an OS.

Desertlakesflying

My Feedback: (28)

Make sure the fuel nipple on the carb is pointing directly at the rear engine mount hole, then adjust from there.

Most people think Super Tigers are junk when they can't get them tuned because of that one simple thing.

It works on every single Super Tiger 2 stroke every time.

NoOneFlysAtMyClub

My Feedback: (32)

One of the best carbs ever designed.

If you give up, I will pay shipping to get it off your hands!!!!!!

Really though, don't give up.

Go to Super Tigre's web site for tuning tips.

If you need more help, ask specific questions here and help will come your way.

pe reivers

The ST90 needs an OS-F plug. No other will do, or it will stop at the most inconvenient moments. And yes, do point the fuel nipple to the rearmost hole on the mounting lug.
Sometimes there is a small burr inside the fuel passage of the spray bar. Clean it out from the idle needle side. Drill size to do that is 1.2mm.

Bax

My Feedback: (11)

Here's how you adjust SuperTigre carbs...it works for ALL of the engines.

http://www.rcuniverse.com/forum/m_1579985/tm.htm

That's how we do it.

You don't necessarily need the O.S. Type F glow plug unless you're using fuel with a 0%-5% nitro content. The large SuperTigre engines (2300 and up) can benefit by one, the smaller ones, not necessarily.

rc34074

My Feedback: (5)

G90 Tuning:

Is the G90 in a cowl? It needs to have plenty of cooling- the rule of thumb I use is to have twice as much outlet area as the head area/diameter - but this is for temperature not over 95F - I don't fly if its hotter than that!! Also, the fuel tank centerline needs to be within 3/8 inch or less of the same height as the carb needle valve and the tank needs to be within 6 inches or so of the back of the engine to get good even running, unless you use some kind of pump or regulator to bring fuel to the engine.

I have flown many (8-10 or more) super tiger g90 engines and do not have any carb tuning problems, but I figured out how to tune them. I use a fox long idle bar plug when breaking them in, and then go to an OS "F" plug. I use 10% fuel but some say they run well on 5% fuel or lower - but I have never tried them on 5% fuel. You should use fuel with some castor in it to protect the engine if you have a lean run/stoppage due to overheating the engine. I think they are easy to tune once you learn the right procedure, but then I have been running these g90s for quite a while .

If you use a muffler other than the one that came with the G90 such as a pitts mufflers (bisson or slimline) you need to pinch the outlet tubes down to get good back pressure - you need to shoot for about the same outlet area that the original STG90 muffler has. Getting the same back pressure lets you tune the carb to get even running throughout the throttle range.

To tune the carb - first you need to get them broken in, which takes an hour or so of running at high throttle with the carb set rich at both the high and low ends, as the instructions say. You gradually lean the high end as the engine breaks in - but be sure that if the engine starts to die to drop the throttle to richen the misture to keep it from dieing lean - this won't really hurt them if it happens once or twice but repeated lean stops will eventually damage the ring and the bearings. Once you have the high end running well you can start going to lwer throttle settings to set the idle. I consider my G90s to be running well when they turn an APC 14-6 prop 10,000 rpm or above.

Then you start leaning the low end until you get a nice idle at 2400 rpm or so. I fly my G90s when they will idle for 30 seconds or longer and still throttle up with no problem with the Fox long idle bar plug in the engine at this point. I keep them a little rich like this until they have run another hour or so in the air. after this hour I change the glow plug to an OS "F" plug and lean the idle down a little at a time - when I get them fully broken in and tuned right they will idle for 2-3 minutes at 1800-2000 rpm. I don't try to idle my engines any longer than that. of course, the high end will get leaned down too - set the high end so with the engine a full throttle the engine doesn't slow down when you pick up the plane and point it straight up for 15-30 seconds.

Also- you need to let them warm up before takeoff - I start mine and run them up to full throttle with the glow starter on it. Then I check the high end setting by pointing the plane straight up. At lower temperatures you need to richen the high end compared to higher temperatures (the air is denser).

Hope this helps.

Ed

Steven H

Wow!

Thanks for the great suggestions everyone. It looks like I need to pay more attention to proper break in procedures. I will set aside some time this weekend to get some run time on it. It also looks like I have it underpropped with a 13-6 Zinger. I have the engine installed in a Lil Toni ARF. So eventually I will want a prop with a pretty steep pitch. Suggestions?

question: Is it possible to mount the high speed needle pointing down? It really messes up the looks of the Lil' Toni sticking straight up out of the cowl. If it is more hassle than it's worth I will just forget it.

also: Any ideas on the glitchyness?

thanks again,

Steve

rc34074

My Feedback: (5)

It is very important that the carb inlet is about the same height as the tank centerline. If the tank centerline is too low the engine will have not pull fuel very well. the two centerlines should ideally be within 1/4 to 3/8 of an inch, with the tank just a little lower than the engine centerline when the plane is level and horizontal. This doesn't matter too much as the plane maneuvers so don't worry about that. Anyway - It is usually a good idea to mount the g90 so its is in its side so the exhaust port of the engine is pointing at the ground (with the wheels on the ground too of course ). Different mufflers will have the muffler tubes coming out at various directions - are you using the original muffler? This orientation of the engine gets the engine pretty close to the height of the tank. Then you need to adjust the tank height to the height of the carb inlet. Sometimes this means modifying the plane structure. that's what exacto knives and spare balsa/plywood etc is for - to fix the design of planes so they work properly the way they need to be to suit your engine/tank setup. I do that with nearly every plane I buy.

Ed

pe reivers

Bax, the link links deeper, and the answers in your FAQ are not so very ST specific.
If you treat a ST like just any glow engine, you are in for a big disappointment. Lots of nitro will blanket some user mistakes, but not all. I have run ST engines by preference as long as I have build model glow airplanes, until I discovered the MVVS line in 2001.
My fuel:
2% nitro, 1% acetone, 18% oil, remainder methanol. More than 2% nitro is a waste of money.
The ST engines need to be set up correctly. If you do, they will serve you well.
Idle:
For a rough start, remove the carb so you can look at the almond cutout in the spray bar. At full throttle, the idle needle should reach about 1/2 way the almond.
Then close the throttle with a 0.8mm hairpin inserted in the barrel. Place a piece of fuel line on the carb nipple, and find theidle needle settingwhere the line will just about admit air when you suck on the line. Any opening of the drum beyond the 0.8mm should produce a rapid flow increase. This is the basic setting of the idle needle from which to start tuning.
Full bore:
Fit the carb again and adjust the idle stop to 0.8mm (see idle), fuel nipple pointing to the rear lug.
start engine, and adjust full throttle just clean running off four stroking.
Close throttle to stop and wait until engine settles. Then pinch the fuel line. If the engine speeds up, close the idle needle slightly (1/16th of a turn! Not more) If the engine sags, open the idle. You may need small idle needle corrections before you can reach the 0.8mm stop.
Now check throttle response.
If the engine stumbles, close the needle very slightly.
If the engine gasps, open the idle very slightly.
Final adjustments should be done with utmost care. 1/32th turnincrements will work wonders. More, and you will overshoot the targets, and you never will get it right.

The whole process, once mastered, takes about 5 mitutes.

MikeMacDonald

I just stole this excelentbit of writing,hopeyou don't mind Best Wishes Mike!

the Wasp

My Feedback: (1)

this site can be really screwy at times. when I first replied the site showed only 1 reply, at that I replied without looking at the date the OP posted, my bad

daveopam

My Feedback: (9)

One of your first post talked about a rattle. If the muffler you have is the one with the flat back it has a disk inside that can come loose. I had a few do exactly that. Usually it will make a black residue on the plane from the metal shavings. The fix is easy. Put a screwdriver in the exit of the muffler and break the disk all the way loose with a hammer. Then you can go in through the opening in the front where it mounts to the exhaust stack. Grab the disk with a needle nose and twist, This will fold it partially and allow it to be pulled out through the opening. I had to do a few of them this way. It didn't seam to make any difference in performance although I suspect there is a little less pressure coming out of the nipple.

David