OS 91FX tunning problem
 

I just bought a brand new OS 91 FX 2 stroke for someone on RCU.
I have had MANY OS motors but this one is confusing me on trying to tune it.
The question I have is the high speed needle is remote twords the rear of the head mounted vertically
The low speed needle is in the front. I am getting no response ajusting the low.
To my suprize I screwed the low end in all the way and the needle fell through the carb???????
It did not stop like my other OS motors have. In the past with my other motors I would screw in the low,,, open 1 turn and ajust from that point. This needle screws in untill it runs out of threads. I needed a needle nose pliers inside the carb barrel to lift the needle to get the threads started back into the needle houseing.

After starting the motor the high needle is ajusted and motor sounds GREAT...... Lower the throttle and either the motor quits or hesitates. Ajusting the low needle has no affect.
Sometimes at a low idle the motor will idle for about 10-15 seconds and than quit.

What am I doing wrong???? I must say I never seen a low needle like this before.

Can someone PLEASE give me some advise???

Thanks much

Hoss

RE: OS 91FX tunning problem
 

If you try to screw the idle mixture adjustment in too far, it will fall out inside the carb. It gets installed from the inside. Please see page 23 of the manual for initial setting. You can also set it by looking into the carb and having about a 4-5 mm gap between the needle and the nozzle when the carb is opened to the full throttle setting and you look into it.

Starting off with the idle mixture set to "stupidly rich" works well. You start the engine at 1/4-throttle or so, advance to full throttle and get the high-speed needle set, and then retard the throttle to work on the idle RPM and mixture. Any idle below 2,500 RPM or so is considered "good".