Franco2fly

I went through it fairly well, but you raise some good questions WRT the fuel lines maybe having a cut.  I'll do another thorough inspection and maybe just replace all the fuel lines since that's cheap.  What about the glo plug?  Really it comes down to do the idlebar or not.  What's the
current feeling on bars?

What bedevils me most is I can start it on the bench, run throttle up and down, Hold the nose straight up advance to WOT, all the traditional tests.  Then back it down to a very nice 2900 RPM idle, move the trim up so its at 3200 RPM, Pick the whole sheebang up walk to the flight line, and move the throttle forward and it dies.  I repeated this at least 3 times and couldn't believe it was doing this.

Finally, the 4th time after letting it heat up a little more, I got in the air, and then started hearing the drop in RPM's at 3/4 throttle, I backed off a bit and landed.  Sure enough, I put it on the bench still running, and with it running at 8400 RPM it just quit with the tank about 1/2 full.

At least the Airframe fix I came up with proved itself.  I installed two braces on the stab like the ME-109 has, and I also fiberglassed the joint.  That piece is solid, now I just need reliable engine performance.


Thanks for the tips.

KKKKFL

Sport_Pilot

This is an ABC engine so it should be broken in enough after three tanks of fuel. Sounds like a fuel delivery problem to me. Air in the lines. Unersized fuel line. Clunk that has fallen off, air leak at the stopper allowing pressure to drop, IE things like that.

That could be as simple as a rich idle mixture. However it could also be due to one or more of the above.

That would happen if you had a hole in the clunk line at about the half tank level.

Franco2fly

While I'm in there checking/replacing all the lines I want to go to a brand new glo plug.  What should I ask for ie High temp/lo temp Idle bar, no idle bar.

Thanks for all the tips.  One thing I don't like about the installation is the level of the carb in relation to the tank.  Since it's inverted the carb sits below the halfway point of the fuel tank.  To offset this I have routed the fuel lines up over the motor mount bracket such that the fuel feed line at one point is higher than the bottom of the crankcase which now is top while glo plug is bottom (typical inverted mount).  If I didn't do this, once the tank is full it would just drain out the carb on the floor..  I'm concerned with how long the fuel lines can be without effecting the pickup.


KKKKFL

Bax

My Feedback: (11)

DO NOT run the engine at 75% throttle for breakin. Only run full throttle at a rich setting for breakin. Run the engine at full throttle with the mixture set to where the engine will just stop breaking back and forth from low-pitched exhaust note to the high-pitched exhaust note. If the engine will sustain running at full throttle when leaned to just rich of peak RPM, run it there. When it can run out a full tank with little change in the needle setting, you can then retard the throttle and work at finding the idle RPM and mixture. Many problems are caused by trying to get a too-low idle. Anything below 2,500 RPM is good. Sometimes, a little higher, depending upon the propeller.

It's not possible to give you an actual temperature or temperature range for your engine. The specific temperature is determined by too many factors. There is only one way to determine at what temperature your engine should be run. You have to run it first and then find out what temperature the engine reaches.

Make sure your engine is operating properly with the performance you expect. Use the exact setup every time...fuel, exhaust system, plug, measurement location, and so forth. If you change anything, the temperature will change. Once you have the engine running the way you want it. Take your measurement. This is your starting point. You will have to take measurements over time to find out how the weather affects it. As the air temperature and humidity change from day-to-day, the operating temperature will change. Eventually, you'll find a temperature range that you can work with.

Engine temperature is not an absolute number for setting your engine. It is only a guide, and can help alert you to potential problems. The only sure way to make sure your engine is running correctly is to see how it's running. An engine can be operating at "correct" temperatures, but not running well.

Finally, use any temperatures you read about, or people tell you, as rough information. The only useful numbers are the ones you actually measure when your engine is running correctly. If your engine is running correctly, then what you measure is correct, even if some else says it's too high or too low. Don't worry about the differences. Each engine is in a unique installation with a unique set of circumstances, so there can be wide variances in engine temperature.

Franco2fly

Thanks Bax, that sounds like very sound advice.
I'm going to start by running it with all the cowling OFF. This after I inspect/replace all fuel lines.  Now what's your recommendation for the plug best suited to ST .61?  Go with the idle bar or not, high temp or lo temp plug.  Gonna stop by the LHS and pick up a length of New tubing, and would like to get a couple plugs while I'm at it.


KKKKFL

Sport_Pilot

Running the lines up then down does not affect the tank height issue.  It only makes for long floppy lines which can fold over from G forces and lean the engine out.  You will either need to lower the tank, raise the engine, or add a regulator. 

Franco2fly

The lines are not that much longer and are tie-wrapped so there's no flop.  Having the feed line higher than the top of the fuel tank just prevents the fuel from dripping out.  It maybe adds an inch to the overall length.  Lowering the tank is not an option, the engine is inverted, this places the carb near the bottom of the aircraft.  Raising the engine is not an option.  The prop would not come out of the cowl correctly centered.  That leaves Regulator.  Don't know what one of these looks like or where I could get one, sounds complicated.

The situation is confounding because I can start the plane up and do all the normal tests, Low to high transition is good with no hiccups, High speed is good initially, Idle is right where you would want it.  Go to WOT and pick it up, point the nose skyward. Not a bit of change in the RPM (I actually expected that it would pick up a bit as the fuel flow would be a little harder hence leaner).  This I intrepret as "Its running slightly rich".

Did all this at the field yesterday, and as described walked the 20 feet to the flight line and tried to take off, when the engine quit.  Didn't even start to roll (No fuel slosh to the rear).  I felt so stupid cuz I repeated this 4 times in about 5 minutes.

Once in the air the RPM sag and subsequent return scared me enough not to fly again, but to only bench test and those results were all over the place with the bottom line being I could NOT get the plane to run an entire tank of fuel.  It does sound like Break-in issues, and I sure did not like the way the Temprature bounced around so widely.  The engine seemed to be running very HOT, but there does not seem to be any significant friction that I can feel hand turning the engine.

Changing out the fuel lines, replacing the plug, and running at full throttle for a tank without the cowling to allow for best cooling is my plan of attack.  Just need to know what folks recommend at the best Glo plug for a SuperTigre ABC engine.


KKKKFL

Propworn

My Feedback: (3)

First of all is there enough cooling? There should be about twice the exit area allowed for air leaving the cowl as entering. Try a McCoy MC14 plug it’s the best all around 2 stroke plug I have found. Hanger nine used to sell it as their brand high performance 2 stroke plug. Make sure the tie wraps around the fuel tubing are not pinching the tubing and restricting fuel flow.

You can set all carbs initially in the following manner. Seems to work for both 2 and 4 stroke engines that have opposing low and high speed needles. Does not work for air bleed carbs. You can even do this with the carb off the engine.

If the carb has a cats eye opening in the spray bar make sure it is facing down.

Back the low speed all the way out so there is no interference with the high speed.

Slowly turn the high speed in until it stops (DO NOT FORCE IT) then turn it out no more then 2 1/2 to 3 turns.

Finally to set the low speed needle insert a 1/16 drill bit or wire into the carb throat and close the barrel until it will just hold the drill or wire in place. Again do not force, use just enough pressure to keep the barrel open that 1/16 th. Now put a small piece of fuel tubing over the inlet nipple and start to blow through the carb while turning in the low speed. When you reach the point where no air is passing into the carb then back the low speed out until you can just detect the air leaking into the carb. This is the initial set up of your carb put it back on and run the engine. This setting will be rich but make only small adjustments at a time. High speed first then set low speed for smooth transition and idle.

Dennis

jaka

Hi!
OS 8 Or Enya 3 or 4. Those are the old stand byes! But there are many other plugs that works equally good, like Rossi 3 or 4 or Nova Rossi 4 or 4A.
Have you mounted the tank according to the "tank mounting rule"?
And are you sure it doesn't leak?

Franco2fly

Just got back from the LHS and I picked up an O&S 6 (hot) and and O&S 10 (cool) and a Fox idle bar..

There is double the exit as entrance air, I might expand this a bit more.  No lines are pinched, but I am concerned that there might be an air leak somewhere, a cut or a nick, and I do want to visually inspect the clunk again to make certain that its ok (Pretty sure it is since motor ran with plane doing a very large slow loop and no engine change noted).  I do suspect the plug,  Last time I ran the engine in the back yard it seemed to perform ok. but I'm sure I didn't run it at full speed for the entire tank, I did notice the RPM changing at the mid range, but just attributed this to limited break-in time.

Experimenting with plugs after ensuring that there's no air leaks will be a big step forward. And running without the cowl on will also allow visual inspection.

I'm pretty sure that the needles are close to where they should be.  I used the Super Tiger Spec sheet directions for setting, but I have to say I like that one where you blow on the tube with the carb only "CatsEye" open.  I wish I had some reference to what a "Typical" head temprature should be.  The big EAA biplane with a ThunderTiger 1.20 head temp runs at 212, however the fins do stick out the side of the cowl, so there's more cooling.  The Zlin, on the other hand has the motor totally enclosed.  Generous air scoop on the front and a hole bigger than a standard 10 ounce coffee cup back where the nose wheel exits. (I'm thinking of enlarging this).  will post results of the next test . 

I want to thank all that have given ideas and tips.  This plane will be fun to fly now that I have the Airframe issues sorted out.

KKKKFL

ec121

My Feedback: (2)

Put the engine on a stik type plane and run it upright for a while to sort it out. A 60 sized stik from Value Hobby or Texas RC planes isn't all that much. I got mine from Value for $105 inc. shipping. They are a little more than that now. Sounds like a fuel supply/ air leak or mounting problem if it runs OK on the test stand. Another thought is fuel foaming on run up. The vibration in flight may be foaming the fuel but not on the test stand or when it is being held.

Franco2fly

Its not fuel foaming, I can see the tank since it extends back into the cockpit, the tank is shrouded in foam rubber.  I would go with air leak but for one thing.  It initially runs fine.  Just starts all this hiccup stuff after 3 or 4 minutes. 

KKKKFL

Propworn

My Feedback: (3)

Foaming fuel is not as common now as most fuel suppliers use an antifoaming additive. If you still find the fuel foaming use an old trick of adding a couple of drops of original formula Armorall to a gallon of fuel.

Dennis

flybyjohn

My Feedback: (2)

I am now thinking it might just be mixture settings. You said that you can start it and then when you put it on the runway and run it up it quits. If you leave it where you start it and let it idle for a minute or two maybe three and then run it up, will it also die. It took me a long time to dial in my carb but now it will idle for the whole tank if I let it and then transition without a problem. I like to test it in pits for at least a full minute of idling without touching it and then see if it will transition. I think that if you get the spray bar pointed straight down and tune the idle to idle for a long time and still transition afterwards, you can then turn the spray bar a bit to make it a little better in the midrange. I think the idle is out just a little bit and it is either loading up at idle or running right on the lean end and when you give it air it dies from too much or not enough fuel. As far as the engine gaining and loosing rpm by the amount you state in the midrange with no input by you then I don't know. I think you are on the right track to take off the cowl and get it running/flying right so that you can see if anything is obvious.

Sport_Pilot

The fuel going down to the engine will weigh more than the fuel goint to the top of the loop so this will not stop the fuel from flowing.  If it does not drip out it may be an indication your low speed mixture is too lean and closing off when you do the throttle cut.  Closing the throttle against a too lean low speed needle will mash the low speed needle into the spray bar on many engines and is not a good thing, may even be the source of your problem.

1QwkSport2.5r

The Super Tigre carbs dont have the same issue as many other carbs in regards to the low speed needle getting mashed into the spraybar. Both needles point at one another in the spraybar.

I think the majority of the OP's problem is a combination of not enough proper break-in time, and improper carburetor setup. To narrow down any faults in the airplane, I run the engine up on the test stand under controlled conditions. Tank centerline dead even with spraybar centerline, felt clunk or sintered clunk, a fully balanced prop (hub and blades), and a tach. On my ST engines in particular, I peak the main needle to absolute peak rpm. Set the idle needle for low idle, 2500 for ringed and probably 2800 for a tapered bore. If transition is rich, I adjust the spraybar in small increments, with the fuel inlet fitting eventually getting aimed at the engine mounting lug front hole. Once it has plenty of fuel/time on it, I reset the spraybar so its straight in. My S90 would throttle very rich in the midrange until it had 1.5-2gallons on it. The spraybar needed to be set with the fuel inlet pointing right at the mount lug to get a clean reliable transition. Now it runs really well with the spraybar straight in at 2 gallons, transition is clean and smooth now.

Tapered bore engines usually require less fuel and time to break-in well enough to fly, but some need a little more TLC before they behave well enough. Don't use a lot of nitro, ST's don't like much nitro. 10% being max, 5% is better IMO. My .90 tolerates 5%, but will not run for poo on any more than that.

Franco2fly

Here's a update on my ST .61 ABC and inverted in the nose of a Hobby King Zlin-42



full side:


On my way home I stopped at the LHS and purchased some new fuel line, as well as 4 different plugs, I got O&S #6 a hot plug
O&S 8 a mid range O&S 10 a cool plug as well as the trusty old idle bar favorite Fox plug.  Once home, I unbuttoned the cowl and inspected all lines, also listened and looked at the clunk inside the tank.  All this passed inspection, so I changed out the plug going for the #10 which was the coolest.  I fueled up a full tank (More on this later)  Fired it up.with the Cowl off.  At first it was running right at that point were its not quite screaming, just into the rich side.  I adjusted the needle valve turning it a little less than a quarter turn and it broke into clean 2 stroke screem turning about 11,900 RPM.  I backed the needle out just a tad to where it was closer to the rich side, this was a few clicks and no more.  RPM dropped to between 10900 and 11,100.  Now I let it run, and watched as the head temp rose.180, 190, 210, and settled at about 215 to 217.
It stayed here and with the new plug (the #10) ran just fine down to where there was about an 1/8th inch on the floor of the tank.  I tested Idle at this point and it would reliably idle at 2700 RPM.  I could drop another 200 RPM but could hear some ticking or knocking.  At 2900 RPM there was no knock and it idled well.

OK, so now I had ground truth with regards to the temp and a decent run, and was certain of Fuel lines and routing.  Running with the cowl off I also noted that at Half tank, the spray bar is right in the middle, so tank height is not an issue.  I re-installed the cowl re filled the tank, and restarted the motor.  This time, since the engine was already hot, the Temp came up quickly.  Before re-installing the cowl I took the dremel cutting wheel to the area where the nose wheel comes out.  I enlarged the air exit such that it is now a square opening 2"x 3.5".  The head temp continued to rise past the 212 degrees noted without the cowl, but settled in around 220 to 225 when running WOT.  At Idle the temp drops down to 212, and at 8000 RPM it only rises to 217.  (It was about 78 degrees outside in the shady front of my garage where this testing took place).

My conclusion:  The plug was the core of the problem, with in-adequate cooling contributing.  A full tank will run the engine at WOT for 9 or 10 minutes.  This is probably more than I need as I rarely fly WOT the entire time.  My feeling is that 3/4 of a tank is more than enough and this drops the fuel level to where it is closer to the optimum level.  Obviously, the real test will be "How does it behave under flignt conditions?"

I'll post a few words after Saturday, my next flying opportunity.

Again I want to thank all those that supplied tips and tricks, I'm sure it served the community well


KKKKFL

Franco2fly

Update from the weekend:

This airplane no longer exists!  Its a heaping Pile of Sh.....  

I was able to run 2 tanks of fuel with out so much as a tick off beat.  Ran one tank at Full throttle, second tank run mostly high, some idle. Ran smooth...  Saturday, fired it up at the field, did all the nose high full throttle test, Idle, high speed medium.  All went well.  Then took off, first 2 minutes engine ran smooth, did loops rolls High G turns, everything perfect.  A couple of low passes, throttle low to high transition perfect.  At about 4 minutes into the flight, I started setting up for landing, turning to down wind and at a fairly low 100 feet, All of a sudden the engine FROZE, I mean dead just plain quit.  I tried to drop the nose and get into a glide, but didn't have enough altitude, and it stalled and spun in totally destroying wing and nose.  At the crash site, I saw that there was about a third of a tank of fuel so it wasn't starvation.  Throttle was at 50% for the previous minute or so, and running around 6000 RPM smoothly.  I have never had an engine just quit like this.  This plane is from Hobby King and it is the last one I order from them.  There were multiple problems with the kit. Weak points everywhere, I had to fiberglass the Stabilizor area, Glass the motor mount area, constantly repair the Nose gear mountings, the Nose gear strut provided did not fit.(too short), the original fuel tank had a crack along a seam and leaked further compromising the integrity of the wood in the nose. (replaced with Dubro tank), I got all the airframe issues corrected only to have engine problems.

The one thing I did see that sums the whole experience, was the back plate of the Super Tigre where it says "Made in China"  What a POS.


KKKKFL

flybyjohn

My Feedback: (2)

I am sorry for your plane loss. It is always hard to come home from the field with one less plane then you went there with. However, please don't throw the engine away. I have built most of my planes from scratch with used or economy engines and if you are thinking of getting rid of the engine, I would be happy to pay you for the shipping and perhaps a little for the engine depending on how damaged it got in the crash.

1QwkSport2.5r

Many people have had good luck with the chinese tigres, but I'm not convinced. Its not to say they're bad, but I trust the italian engines. My S29 and S90K have been good engines once well broke in. The S29 was the better mannered of the two, the 90 needed 2 gallons to transition good with the spraybar straight in. Until it got to 2 gallons, the spraybar had to be tweaked quite a bit.

Sorry to hear about the crash. Its always hard to crash anything. I lost one of my RC Cars to a radio failure runaway. Hit a curb at about 50mph and turned the chassis into a taco. Sad, it was one of my favorites...

Franco2fly

It was pretty soft dirt so the only damage was an ear of the muffler stack.  I had previously purchased a Non ABC Chinee ST and that one gives reliable performance.  I never liked the fact that right out of the box, there were times when I could not turn the engine over past TDC.  It always gave me spilcus that the engine would just quit, and this was usually when running at mid range throttle settings.  This last time, I had a New plug, new lines, Checked the clunk in the New Dubro tank, new fuel.  I had run two tanks at the field the previous Wednesday, Ran another tank on Friday, all with no problems.  Before putting it in another plane I would need to run this engine for at least half a gallon constantly or continually for a good hour running WOT.  Then see if it can run reliably at half throttle.


Thanks for the condolences.


KKKKFL

Franco2fly

Maybe its the gas...  I just cannot get a reliable run out of ANY SuperTigre.  Two weekends ago I purchased a plane with a .91 Tigre, Thought I had it running good in the dirveway, Good idle down around 2750 solid transition running a 13/6 nylon prop, Top end tach'ed out around 11100 at full tilt, so I backed it off three clicks 10900 on the ground.  But here's something I just don't understand.  Pinching the fuel line it would immediately die.  No increase, just stop....  No matter where I put the needle valve it always did this.  I tried flying it and as soon as the plane left the ground the rpm increased slightly, ran for enough time for me to get some altitude, thankfully, but then died so I had to "Deadstick".

On the ground, despite running two tankfuls, it did the same thing.  What is it telling me when a pinch immediately kills the engine?  I have tilted the spray bar from straight down the throat to a slight tilt maybe 15 to 20 degrees.  This doesn't seem to make any difference.  I have changed the glo plug, now using an OS #6 "cool" plug, this seemed to help the idle but what I want is the engine to run a tank of gas while in the air.

Any tips or ideas welcomed.

As a final note, I got so fed up, with this nitro experience, I installed a gas DA-20 in the plane.

KKKKFL

mike109

G'day

I have a Super Tigre 51 which was behaving very similarly to yours. It still had the original ST plug in it. It would idle happily and rev out to full revs but as soon as I took it to the flight line and advanced the throttle it would stop. No amount of tuning made any difference. In desperation I put the only other plug I had into it. An OS F four stroke plug. It was a different engine. It would run, idle, transition and hold full power. So I flew it. It was MUCH better than before but not totally convincing so a couple of weeks later I bought some Enya #3 plugs. I put one in and it was an even better engine. It was perfect. Low idle, great transition, good top end and it would empty the tank.

I did the same thing with a friend's OS 75 AX and another friend's poorly running inverted ASP 91 four stroke. The Enya #3 may not work in all engines but with low nitro (we were using about 10%) and in the engines I have tried, it is a great plug.

Mike in Oz

Franco2fly

Enya #3 its on my list...  sounds like plug issues are the area to focus in on.  Can you do a pinch test and tell me how it responds.  According to everything I've read this is the best way to get the needle valve spot on..  it goes like this.

You fire up the engine, turn the needle until the engine max's out. now back off two clicks. It should be just below full top RPM's as you listen.  Hold the plane upright, and it breaks into full top RPM.  OK now back on the deck.  Pinch the fuel line. the engine should immediatly pick up to full RPM, release the pinch and it should drop back into your previous setting.

This same procedure is used to set the idle, but the increase in RPM on pinching the line is a little slower.

With mine, the instant I pinch the fuel line the engine STOPS, I mean instant quit.  I cannot get ANY SuperTigre to follow this.  I am using 10% nitro, which is actually high by European standards but its what's available locally.

Moving the spray bar has made no difference.  What's worse is that even when I get it running on the ground, I still am anxious to put the plane in the air since the engine will start to "Unload" somewhat.

KKKKFL

jester_s1

Franco2fly, your situation sounds like a classic "too lean" setting. I understand you're a tad rich of peak with the plane sitting still on the test stand, but that may not rich enough for that engine with that fuel in that plane with that tank. The engine let you know on the ground that it was too lean by dying immediately when you pinched, and then in the air when it unloaded it died from being lean. Do you recall if it was hot when you picked it up after the deadstick? If you have a tach, start around 500 rpm rich and see what you get. You're a little underpropped (not badly, but ST .90's are very torquey engines) so you're probably unloading a lot in the air. You may find that for optimum power in flight you need to be 800 rpm rich or more. A couple of other tests to do before flying in addition to the pinch test is to point the nose in the air and listen to the rpm. If it increases to peak you're at least very close to the optimum setting, but if it stays the same you're too lean. You should be able to hear a slight and consistent increase when you point the nose up and then hear it come back down when you go horizontal again.