While your waiting on Twinman to answer I'll put in my 2 cents.

I had a Super Tiger .90 in a TF P-40 inverted.

1. Ran totally stock including carb.
2. Ran 15% red max fuel
3. 13.5x8 Graupner prop
4. Ran great, started easy, (mine would flood easy so look at your plumbing set up to see the tank center line).
5. Used a hemostat to shut off fuel when shut down because fuel would siphon out due to tank level.

My experiences with the stock carb is wrought full of nightmares and successes. Else where in RCU I have posted comments on using the OS 7D carb and the ST .90. From what you describe I would say you have an air leak someplace within the carb meaning check the needle valve orings, check the carb seat (use medium thread lock to get a good seal from carb to block) clean the carb and make sure your not fighting dirt or foreign objects and filter your fuel into the tank from your fuel bottle and again from the fuel tank to the engine. (and use and install a new plug whether you think you need to or not)

Set the carb to the stock setting, I think there used to be an owners manual posted on the supertiger site a long time ago. I had one floating around someplace but probably gave it away. Once the carb is clean and back in stock configuration start the motor up and document every detail you can about how many times you prime how many flips ect. Tune the carb according to the manual and start the low end procedures i.e....start, tune bring throttle down to idle punch full throttle see if the engine stumbles or if it sags ect...

Once you determine where you are in the low end tune move the low end needle in 1/32 movements. Any more than that and you will pass the sweet spot.

The reason I document all my procedures is to compare when you finally get frustrated and yank the motor out and place it on the test stand and run the engine again. the comparison between your install and the test stand will tell you if you have problems with your install. IE tank centerline, plumbing problems (fuel lines making too tight of turns, pinched lines ect.)

Many people will not or do not have the patience to do all this. They usually run down to the hobby shop and buy an OS sell the Sup .90 and from then on bash supertiger. But tuning the OS .61/.90 FX is basically the same you need to know where you are in the tuning procedures and the only way to do that is document your efforts.

The stock carb is a good carb and the newer versions are better, but sometimes the install can make them a little difficult to tune on the low end. Many people say I can get mid to top end and weak or unreliable idle, or I can get a good idle to loose mid range and be well below peak RPM on the top. They do not seem to be able to get both


Just my .02 cents worth.

JDS