I have heard of various, easily resolved issues with the larger ST engines, some of which I'm considering for my G3250 that I just bought and installed in my Goldberg Extra 330 77".

I have run about 4-5 24oz. tanks through it, the first 3 of which were with standard Omega fuel, super rich, and the rest of the time was in the air with Omega ST fuel. I can't seem to get past the engine leaning out in the air. I start it out really rich on the ground, no where near its peak RPM, and then in the air it sags out, especially during high alpha and high G maneuvers. The fuel tank is up as high as it can go.

I know it is still breaking in, and it's going to lean out, most likely, as it does so. However, I would like to be able to fly with it in the meantime. I've thought about putting a VP-20 pump on it, since I have one readily available.

Please, no Super Tigre bashing here, okay? I like Super Tigre engines and have always found resolutions to any issues I've had, and they usually run just as well if not better than their competitors who charge an arm, leg, and first born for less HP!!!!

That being said, your suggestions and input are welcome. =)

Some things to consider: How old is your engine? Italian or Chinese production? Does it have the insert inside the carburetor to reduce the opening? What muffler are you using? What size fuel line are you using (inside and outside of the tank)? Did you start out with very rich low-end and top-end settings and set the high-speed first and then work on the low-speed?

The answers to these can affect how your engine runs.

I blend my own fuel. No nitro 10% Klotz oil. Use an OS#8 plug.

Good luck

Keithw

I would start by increasing the volume of fuel to the engine. Do this by using the larger fuel line. You will also need to get the next size up brass tubing for the tank. The stopper and back plate can be drilled out in the tank. I also drilled out my clunk and removed and drilled out the nipple on the carb. Mine was not leaning out but these things increased the performance and reliability of my engine. BTW I run Byron ST fuel an OS "F" plug a Zinger Pro Series 18x6 prop and a Bisson Pitts style muffler.


David

Bax,

The engine is a brand new, Chinese product, that I just purchased from Tower. I do not see any sort of insert inside the carburetor. I am using a Bisson Pitts-style muffler designed for that engine. I am using standard (medium?) size silicone tubing. I started out with the factory setting on the low-end and very rich on the high end for break-in and I have since leaned out the low-end about 1/2-3/4 turn and the high end I've leaned so it runs smoothly but quite far from its peak RPM, and it still leans out in the air every time, especially during high-G maneuvers.

Many times, the low-speed needle comes set too lean from the factory. The "factory" settings on almost any model engine cannot be considered to be in any way reliable. You have to work with them. With SuperTigre engines, you MUST start out with a too-rich low end and a very rich high end. Get the engine running and up to full throttle. After 3-4 24-32-ounce tanks of initial running, you should be able to lean the engine to just rich of peak RPM. THEN you reduce the throttle and work on the low-speed needle.

Going lean during a flight is usually a symptom of a slightly-lean carburetor setting. On SuperTigre engines, if the low-end is too lean, it will affect the high-speed setting. When first starting to work with the engine, there's no such thing as a too-rich low-speed needle setting.

Your fuel tank may be too far from the engine, and the fuel tubing may not be large enough. We use large silicone line and and large brass tubing inside the tank. We usually have to replace all the tubing in the tank to get the larger stuff to work.

Great advice Bax, thank you!

I was just taking the fuel tank apart a few minutes ago and found a slice in the fuel pick-up line next to the brass tube leading out of the tank. Methinks that may have contributed to the problem...

I will use what you told me when I go out tomorrow to try and fine tune the engine. If I'm still having problems, I'll go with the larger fuel line and brass. If it persists after that, I'll be in touch =)

Thanks again.

-Pat

Check your tank location, if the engine leans with positive Gs then its too low. Reduce prop load or install a venturi sleeve for better fuel draw.

Keithw,
Golden words, the only difference is plug, I use OSF.

Flying my Yak-54 last evening. Crankshaft broke in flight on my 3250. Lost prop drive, prop, spinner. She got alittle tail heavy but got down with no damage. RPM went to 1,000,000. Think I will buy OS 1.60..

My friend is flying a Su-26 with a St-3250 converted to alcohol. He has done this with all his St engines (he uses 3 ST3250's right now and a 2300). I will find out from him about the conversion and more details. His motors run incredibly well.

Don D, are you within the 3 year warranty on it? Or, most likely, you probably just past it the day before that happened... =( Murphy's Law.

mtwister, please give me some details on that conversion, I would be very interested to hear about how he acquires and mixes his fuel and what is involved mechanically. Also, how is performance affected?

I have "Been There, Done That" on a 3250. I tried all that clunk drilling, large fuel line, spray bar turning, glow plug , pump/cline, proper fuel stuff and did not do a darn thing and was a waste of time, money and effort to solve the problem at hand. The simple fix was a carb change. Now doing all that stuff would probably make the engine more efficient but IMHO would only mask the initial problem at hand.

So, I took the plane out yesterday and flew several times, each with a miraculous dead-stick landing that probably took a year off my life for each one due to heart damage...

I had our resident 2-stroke expert helping me. We got it running nice on the ground, and each time after a few minutes in the air it would start to sag out and die. This time it didn't matter the flight attitude, maneuver, etc. It seemed to be leaning out after about 3 minutes each time. We'd richen the top end a couple of clicks on the ground, start it up, and then it would be running a little rich. We tried leaving it running a little rich, and then it would again lean out after a few minutes. We tried adjusting the low-end, we richened it up and leaned it little by little until the throttle response was smooth.

The airplane is a Goldberg Extra 330 77" (about 1/4 scale). The cowl is very open in the front and there is an additional large opening under the exhaust stack.


---Cyclic: What carb do you recommend? The Perry carb?

I use the ASP 108 or ASP 120 carb as it is very economical. The Perry carb is also a good choice.

Keithw

Hi!
It is unfortunate that you are experiencing trouble with your ST-3250.
I don't have that engine myself, but I do have extensive experience with ST-3000 engines, which are identical apart from bore and stroke.

The leaning out problems you experience in-flight could be due to fuel starvation, overheating or simply the fact that the engine has not been broken in yet. Do yourself a favor and give the engine a couple of hours of bench time. STs takes a long time to break-in. Typically I use at least a gallon of fuel before installing the engine in an aircraft. As you have noticed it is time (and money) well spent.

BTW, during the break-in process, large SuperTigre engines require fuel with a minimum of 15% oil content by volume. It is only AFTER the break-in that low oil content fuel should be used. In the manual it is recommended to run the engine on the 15% oil fuel for at least two gallons’ worth. I agree wholeheartedly with this. Three to four tanks may be enough for other brands, but NOT for the large STs.

As Bax wrote, make sure that you use large diameter fittings and fuel tubing for your fuel system. If you don't already have it, install an OS F glow plug.

The big STs generate a lot of heat and efficient cooling is a must. Make sure that the cooling air is directed through the cylinder fins.
Block the air inlet opposite to the one where the cylinder is. It doesn't contribute much to cooling, but may restrict airflow due to too little difference between entrance and exit surface area.

The Bisson mufflers provides relatively little back pressure so you could try to block or restrict one of the outlets in order to generate more muffler pressure to the tank. I do that with my ST-3000s to good effect.

I have not found it necessary to change carburettors on any ST of mine. They do take some time to get to grips with, but after that they work perfectly.

If you don't have it here is a link to the [link=http://www.supertigre.com/manuals/supg0268-manual-v1_1.pdf]ST-3250 manual[/link]. Read it and follow it religiously.

/Red B.

I am having the same problem with my GB 330 I have an OS160 installed and it will lean and die at about 3 minutes into the flight. I have tried the same remedies, large bore tubes and a short run. I did find that the needle valve was vibrating to a different setting in flight so stabilizing that helped a bit. Richening the low end helped. The desighn of the plane puts the tank axis below the carb on a side mount set-up. this probably is a major part of the problem. A pump might do the trick here or use of a header tank.

I went to the SuperTigre site and followed its instructions for break-in with respect to the G3250, (link is on Tower's website) and conducted the break-in according to their instructions. I figured that it was more up-t0-date than the manual that came with it since it addressed specific issues regarding this engine.

I have replaced the fuel tubing with large diameter tubing, although the fuel nipple on the carb is so narrow in diameter that I have my doubts about whether or not it will help unless I bore it out, like some have mentioned. I'm hesitant to do so, since there really should be no need to make such alterations to stock equipment, but I'll keep it in mind...

I pinched the tube on one of the exhaust outlets of the Bisson muffler.

With these changes in effect, I'll report on the difference it makes, if any. I do have a VP-20 pump ready for use; however, using the backplate mount, I would not be able to use it on the backplate. I may be able to find a different place for it, such as on the front of the crankcase, but it will need to be altered to do so. The pump is not wide enough and one of the fins on the front piece of the crankcase interfere. I could just screw it onto one of the screws and see how it goes, but my fear would be that it would loosen and the screw would fall out.

no report\??? p-diddy\??

Oh wow, I had forgotten about this thread, sorry!

I tried the pump, I tried the large fuel tubing, I tried pinching off one of the exhaust tubes. Eventually, I gave up on the big ST and converted to a 40cc gas engine from BCMA. Now, I was told I would not notice much of a power increase, if any, but that was certainly incorrect!

Sorry, I tried pretty much everything and eventually decided that I would just take a loss and sell the engine on Ebay. I do miss being able to start on one flip, but it's all a trade off... Fuel is much cheaper now =)

Good luck to everyone else out there who has the big ST's. As far as I can tell, if order a ST, you have a 50% chance that you'll get a nice running engine out of the deal. That's been my experience thus far, after having had four of them.

----------------


Now that the Tigres are being made in China with lower labor costs, etc., how difficult can it be to upgrade the entire engine line with carburetors that are better optimized for these engines? Do away with the oversize carbs and provide something that will pull fuel adequately from a normal distance. That extra 300 rpm that is generated with the oversized carb is just false advertising anyway. What good is an engine that spins faster with the nose level, but doesn't have sufficient fuel draw to fly leaned out enough to realize those extra rpm? I would like to see carbs designed for alcohol fuel that have their own built-in diaphragm pum and regulator system. Something smaller and lighter, possibly modular, that can be used on engines as small as a .46 to .53. It can be done and easily at that.

I've been in the hobby for nearly half a century. I remember when Super Tigre engines came with great carbs. The easiest solution would be to abandon the old designs and to rebadge Sanye, or another brand of GOOD carb, Not GMS, and get on with selling these great engines.

Fully half of the folks I've talked to about ST engines have had problems over the past decade or more. All of them cannot be idiots. If the price is increased another $20, so be it. At least folks would have usable engines without having to be an engineer in order to make the present carbs work. It makes no sense to destroy a brand's reputation just to make a few more dollars in the near term.

HEY!!! I had a NELSON Q40 with a ST4500 carb on it and it ran great!!!! Idled at 4000rpm and 27,400rpm on the top end with a carbon 7.4 x 8 prop. I don't see what the problem is here?[sm=shades_smile.gif] I have ran big bore Supertigres for years. Yes the O.S. 7D is a great replacement carb. I have had no problem with the stock ST carbs but have incorporated a Perry/Conley VP-30 pump and a Electro-Dynamics EDR-103 Glowlite on-board digital glowdriver. 0-5% nitro and 15% Klotz KL-100 lube. FOX R/C LONG w/idlebar ( thanks Duke!!!) or O.S. F glowplugs. Absolutely no problems but now that I have written this comment I will probably have nothing but problems! The NELSON story is absolutely true!

The problem:
Super tiger S3000 had the same carb as the S90K with 9mm venturi bore = good fuel draw[sm=thumbs_up.gif]. The G3250 has a gigantic 12mm bore and thats the main reason for it being more difficult. Big bore carbs. are good for very high topend but not for normal sundayflying mostly at the mid throttle.
If one makes a sleeve that reduces the bore to 10mm I am pretty sure the engine will not have any fuel draw problems and the midrange gets much better as a bonus.
Replacement carbs:
OS7D or Mag108 carbs are good for this engine. Both need an sleeve to fit in the crankcase.

It you use a tuned pipe this engines makes the same power as a modern 50cc gasoline engine and a whole lot more than most 50cc chainsaw conversions.

I went through two st3250's and followed the on line instruction on break in and went to large fuel lines and still had all kinds of high end trouble. I finally broke down and spent the 350.00 for the 35cc 2.13 Cu. Inch OS engine and it runs very nice in the same plane and fuel system that burned out two st3250??? I love my smaller ST engines but everywhere I go I hear the same horror stories about the 3250.

I regret having purchased the ST3250 in the first place now that I've tried gasoline-powered engines. I think that when you get into the 1/4 scale or bigger planes, it usually just makes sense to buy a gas engine. You spend more in the beginning, but the fuel is cheap and burns more slowly. Either that or buy a Moki, if you must have a glow engine.

I've had four gasoline engines now and all have been powerful and reliable, (except the 40cc, which has suffered some odd mishaps, but I digress...).