I have a ST 2500 on a Patric Ultimate that won't idle or transition worth a crap. I sent it back to ST and they replaced the carb. Still dosn't run right. Any suggestions on replacement carbs? Any suggestions for a strong running motor for the Patric Ultimate?

Hi,

What fuel are you using?

Red Max 15%

My ST 2500 wont run for crap unless I use the low oil content fuels made specifically for larger ST engines. Have you tried any of them? I currently use Omega Super "T".

I fly a 20 lb Byron Husky on mine with no problems

I haven't tried anything but Red Max but I will. It's worth a try. I appreciate your advice.

The "Big Tigre's" don't like any more than 10% nitro and 10% oil. Try the special blends for them as recommended. I put an OS 7D carb on mine - could never get the stock one to work. Also found a metal chip under the head sealing ring courtesy of the factory! Good luck.

Hall

There is a new SuperTigre support forum. You may want to consider moving this thread there for better results. There is already some interesting reading on large Tigres there.

Cheers!

Galen

I also replaced my two 3250 carbs. One has the OS 7D and the other is a Perry. Both work equally well and the engine now runs and transitions great.

You got to use the fuel blend for the Super Tiger,I belive it uses 8% oil and 10%nitro.I used to get it from Byron.I don't know who would make it now.

I`m using 10% Klotz with 90% straight methanol - no nitro - in both my ST3000 and ST4500 with no complaints. Both motors have their original carbs.

Alan W

It's not the fuel that's causing your grief.

It's the CARB. PERIOD!!!!!

I know. I have 2 big cats. A ST2500 and a ST3000.

I have run different fuels in both of them at different times. This was before I broke down and listened to the guys who told me too buy the OS 7D carb. You see; I'm stubborn. I was convinced that I could get the engines to run, if I would just tweek the needles the right way, or if I tried a new fuel, or if I tried a new plug, or a different plug, or a different fuel.

ALL BULLS**T!!!!!!!!

I finally got tired of fighting it and went out and bought two brand new OS 7D carbs. My problems went away faster than a fart in a hurricane. And I'm not lying or pulling your leg.

One other thing to consider: If you have the engine mounted inverted, your going to have problems. The engine will never idle well and it will burp, fart, wheeze, cough, and gurgle on transition. Try adding on-board glow, if you must mount it inverted. Or mount the engine just slightly off-center. This will move the glow plug away from the bottom and prevent fuel from "pooling" up around the plug and drowning the engine. With the engine mounted inverted, the plug is dead center on the bottom of the head, and it becomes flooded and cools off quickly. This causes the burping and farting and often the dreaded deadstick on final approach.

I am currently running Omega (pink) 5% fuel in the ST2500. It runs just fine. It turns an APC 16-8 at 8300 RPM. And I fly at exactly 5973' above sea level, where the air is thin. Engines lose about 15-20% power at this altitude.

I am running Cool Power (green) 15% in the ST3000. It runs just fine. It turns a Zinger 18-8 wide blade at 8600RPM and a Zinger 20-6 at 8000-8100RPM. Sometimes I will run Cool Power 10% if the LHS is out of the 15%. The engine doesn't run any different.

And by the way: Higher nitro makes the engine run COOLER. Not hotter, as most people think. I have put a temperature sensor on the head and the glow plug, and measured temperatures with different fuels.

Nitro is kinda like the octane that is in the gas you run in your car. Higher nitro, or octane, makes the fuel burn SLOWER; therefore creating a longer burn on the compression stroke. This makes the actual combustion process cooler; because it burns in a larger space. It burns in the entire cylinder, rather than just in the top of the head. This lowers the pressure of the explosion, which lowers the heat.

The reason that higher nitro gives you more power, is because it does burn longer. It produces the power slower, but more consistantly and for a longer period of time on each stroke.

Just get an OS carb. or another suitable replacement, and you will be happy.

Hope this helps.

Well Mr Rcpilet it may be Bull***t to you living in mile high city but here in Florida at sea level that carb works perfect *AS LONG AS YOU USE THE PROPER FUEL*> We have half a dozen of them runing with the stock carb, And one is upside down in a Pica Spitfifire and even that one runs great >*WITH THE PROPER FUEL* Nuff said.

MR. rcpilet... I have the same carbs that came with it... No problem with mine... Maybe you just had some bad carbs on your motors... It's all the fuel.... Mix your own and your good to go... ST wouldn't install a freaken carb that doesn't work.. Sorry but they have been in business for way too long to scimp out on the carb... .. And like the old saying goes.. If you change a new carb, Why not change the head, Sleeve, crank, case while your at it...
So it leads to this.. Get the right fuel and you won't dead stick the thing no more.. Simple.... I run no nitro in mine and it's fine.. I also run it a little rich I never had a dead stick yet from my 2500, 3000 and 3250's....I have 7 of them there the best.. Well almost.. L8ER.. That's my 2 %

ST is no longer. Part of the reason is that they made great ARF engines. It took much tinkering to make them right. The Big ST have had carb problems for years, don't think so?? Look at the "suggestions" GP has on their web site for making the ST2300 run right. BY the way if you get one right its a VERY GOOD engine.

I agree with you.. But From what I've seen at the club.. There's about 10 maybe 12 of these motor.. 2500, 3000 , 3250 and even the 4500 and I found that when poeple star the the right fuel right away and break them in ( wich is more then a gallon of fuel)
There bullet proof and do run reliable... One guy converted one to gas.. It runs ok... now I have no ideal if they changed the carbs for different years or not , Maybe that's why... I do agree some run like a bag.. you have to spend some time with these..
And I'll tell you something, Most poeple buy these motor's used..
And when they do the carb and the motor has been taken apart and probably put back together wich is no problem to to but you get a couple guys that don't know what there doing and let them take the carb appart.. Well... o-ring is gane after that... Any ways... I have luck with mine and so does a few other poeple that I know... It's all fuel And I'll stick be that..