rctmpilot

So I've got an old Morris Hobbies Su-Do-khoi with a Super Tigre .61. We had some trouble getting it tuned up initially, but after some fiddling, we got it winding out like a champ. Idle to full throttle many times with no problems. But every time i take off, ill get up a hundred feet or so to start playing and it kicks out. Every time. Doesn't matter how long i let it idle, or full throtle on the bench. As soon as i full throttle in the air it dies. I did some searching and it seems like a problem that some have had, but i never really found any solid answers as to why. One guy put a Tower Hobbies carb on his and it pretty much settled out. Any other opinions? Anybody else have this problem? It seems like a real strong engine, and i hate to give up on it. I do have a MDS .61 in reserve, but thats dog eared for my Ultra Sport 60 that i'll be finishing up this winter.

And if the carb is the problem, is there any tweeking i can do to it, or is replacing it the only option? And if so, can anyone point me in the right direction to get one? Sorry for all the questions, but this one has me and the guys at the field baffled!

Phil

1QwkSport2.5r

I think most problems people have with Super Tigre engines has to do with using the wrong fuel and glow plugs in them. Most of them don't like much nitro and usually need hot plugs. The Carburetors are easy to set if one understands the way they should be set. The process is a little different than most typical 2-needle Carburetors. I set the main needle with a pinch test - at WOT, lean to peak then back off richer until there is a slight rise in rpm. Set the idle needle for a low reliable idle - 2,700-3,000 is reasonable. Lower than 2,700 tends to not work well in my testing. Adjust the spraybar if the midrange is rich. Small incremental adjustments to a long way in my opinion. If the engine has less than 2 gallons worth of runtime on it, it probably isn't broke in well enough and will likely need a richer mixture. None of mine behaved real well until I got 1-2 gallons through them but mine were all made in Italy.

RCPAUL

My Feedback: (1)

Have you tried an OS f plug?

paul


i love STs!

rctmpilot

thanks for the replies. I'm hoping to get a chance to work on it tonight when i get home from work, and I'll give that a shot. And no I havent tried a diferent plug, but my Father in Law has an OS f that we'll throw in.

rctmpilot

ok, another question which is probably pretty silly. Is there anywhere i can find an exploded diagram of the carb and engine for this? I havent got a lot of experience with glow engines (I have a GMS 40 that i have yet to get running right, I believe thats a junk remote needle valve, but thats a different headache for a different day, and an OS .70 4-stroke that has always run like a champ) and I'd like to have something to reference when i'm working on it. I did a quick Google search but couldnt really come up with anything.

1QwkSport2.5r

Here's the parts list of the newer G61 carburetor. The S61 is very similar though the idle needle holder and needle is slightly different.

http://downloads.hobbico.com/evpl/su...1-exploded.pdf

rctmpilot

Thanks!

aspeed

Some good reading. http://www.supertigre.com/faq/product-faq.html#q22 I couldn't just copy the two related paragraphs but the whole thing is a great educational waste of time. Other carbs may work, especially the smaller bore ones. Then you lose power. The Supertiger carbs are fine once you get them figured out. I find they like a stream of oil coming out to make them happy. I have got better at deadstick landings, so they are good practise? I don't fly low over the bushes anyway. Learned that one a long time ago.

Bax

My Feedback: (11)

Usually, if the engine quits after a short period of time, the most common reason is a blocked vent. The engine draws fuel and a vacuum builds in the tank because the blocked vent won't allow air to replace the fuel drawn. Eventually, the vacuum is strong enough to prevent the carb from sucking fuel out of the tank. The engine leans and dies.

If the engine is overall too lean, it will quickly overheat and quit.

If the fuel pickup in the tank is too close to the rear of the tank, the engine will quit on acceleration...usually this happens at the beginning of the takeoff roll, but can happen any time you accelerate.

You need to do some careful detective work. If the engine will run "all day" on a test stand but not in the airplane, it's not an engine problem in, and of, itself. You have a problem in the airframe/engine/fuel system combination and need to thoroughly go over it.

Mr Cox

Sounds to me like it is simply set too lean.
Set it richer on the ground and try again...

Granpooba

My Feedback: (5)

Ditto ! Have run many Super Tigre engines in my life and found that they like to be leaned then turned back to be a little on the rich side. Don't ask me how I know this, but I have learned the hard way.

BillS

Solution for rich mid range.
I have been able to reduce a rich mid range by using an open '90 degreeT' between the muffler an the carburetor. The solution is repeatable and very little trouble.

aspeed

An open 90 degree T would be really just running on suction then.? Maybe just a slight bit of pressure from the muffler, and a bit of oil spray on the motor ;-) I don't think I am quite getting it.

BillS

My homemade manometer seems to indicate the same top end pressure as a 'NO T' system. I have not noticed any oil spray on the engine. And yes I was surprised. The homemade manometer also indicates pressure at idle. Takes only a few minutes to test and the 'T' can be removed if undesirable.

I am not selling anything. A 'T' costs a dollar at the hobby shop.

aspeed

Think of all the tens of dollars you could make :-) I will have to try it some time. I suppose opening up the outlet of the muffler would give a similar effect. Less back pressure. It would be permanent though, if it doesn't solve the rich mid range.

BillS

It is a five minute experiment that I found to only affect mid range.

jaka

Hi!
You are probably setting it too lean! You have to hold the plane straight up (nose up) and then set the engine a little rich.
Use 5% nitro fuel and an OS 8 or Enya 3 glow plug (there are many others that work equally well but those two are the old stand byes).
Carb is as every other carb that uses two needles, nothing more nothing less. But...you can also turn the whole fuel intake orifice ,and that way alter the way the engine responds, but do not do that!!! The carb functions just perfect as it comes.

Another probabillity is that the engine is worn out and thus isn't as good "air pumper" as a new engine is.
How is the piston to cylinder fit ?? Is it worn .then.the engine cannot pump air/fuel the way a new engine can and thus stops in the air.

1QwkSport2.5r

You're off-base in regard to the midrange adjustment (spraybar) as some engines do require the adjustment. Some engines work fine with the factory spraybar setting and others need adjustment whether for breaking in or certain props. I had to adjust the spraybar on an ST S90K for a leaner midrange during its post-bench break-in because the midrange was so sloppy. After it had 2 gallons of fuel through it the midrange ended up being too lean necessitating putting the spraybar back to being straight in. My ST S29 never needed the midrange adjusted as it worked fine from new. Not saying it's 100% wrong to not adjust it, just saying its not right to say you never adjust it period.

a70eliminator

Your engine requires much more fuel when under load (in the air flying) vs. reving it up on the bench, perhaps your fuel tubes got pinched a little coming out of the tank, or lines themselves, maybe the in tank clunk is gummed up, overall I think your engine is starving for fuel when under a load, try another tank or go over all your entire fuel system.

computermonkey

My Feedback: (90)

What glow plug are you using in the engine. In my 90 I've tried several with the Thunder Bolt R/C long idle bar being the best on 0% (summer) 8% (winter) fuel.

I had trouble when I take off hit full throttle and climb it would give a small stream of white smoke then die, but this glow plug took care of this.

1QwkSport2.5r

You need to use long reach hot glow plugs and set the needle richer than other engines. I set my Tigres about 500-600rpm rich of peak using a tach or the pinch method. I quit having stalling problems from too lean of a needle setting. ST carbs seem to have finer threads on the needles than other carbs so the usual 2-3 clicks isn't enough.

computermonkey

My Feedback: (90)

I've used OS, Enya and Merlin's glow plugs. The Thunder Bolt R/C long idle bar has worked the best in all types of weather temperatures and fuel combinations.

captinjohn

Computermonkey, I agree 100% Merry Christmas & a Happy New year !

1QwkSport2.5r

I've never had much luck using idle bar plugs in any normal 2-stroke engines personally so I never recommend using them. Usually idle bar plugs hinder performance a tad bit but likely not enough to matter.

Baffle piston 2-strokes and 4-strokes they work great in my experience though.

Merry Christmas folks!

computermonkey

My Feedback: (90)

Hello 1QwkSport2.5r

One of the issues I've seen with Super Tigre's beside people not knowing about the mid-range fuel adjust and using to high of nitro is the schnuerle ported engines are bad about fuel squinching the glow plug.

With these problems address they are every bit as powerful, long lasting as any other engine out there and a whole lot lower in price.

Merry Christmas