I have a Saito 80, OS F plug using Performance Plus 15% fuel, APC 13-8. The engine has about 3/4 gallon through it. When the top end is adjusted properly (3 or 4 clicks rich) the idle must be richened considerably in order for mid-range to not be lean. When idling this rich it will run for15 seconds or so then die rich. In this state the idle must be set high enough so that I have to chase it around on the ground. If the idle is leaned so as to idle properly, the mid range is lean. Another fellow in our club has the identical problem with his Saito 80 and has been wrestling with it for a year with no solution. Any thoughts?

Switch to a 13x6 and all will be well, the airflow velocities through the carb are too low with that much prop, this makes the fuel draw too low so you compensate by setting the high end overrich at full throttle. Then when you go to part throttle where the fuel draw improves it is too rich. If you really need to load it that heavy, it needs a Cline regulator. You're sort of asking it to be a 100.

....I sure wish i had the answer to your problem. I
had the .80 in a Cub, and played with it for years
and never could get it to run right. Just like you, I'd
get the high speed set perfectly (just a tad rich) and
get a "happy" idle...and it would NOT transition
properly....most times it would "pop" and die. When
I did get it running half-way decent, and in the air. If I
throttled back, like in a spin....99 times out of 100 it
would die and deadstick.

I tried on board glow...no help. I had a perry occilating
pump on it for awhile, and it seemed to help, till the
bracket broke a couple times from the vibration.
Finally, after about 8 yrs (I'm not kidding, I'm pretty
stubborn) I yanked it out, and put in a new Magnum .91
4-stroke. I loved the plane. PROBLEMS SOLVED ! Same
fuel tank, same fuel lines, everything same.

I haven't touched the adjustments or the plug all year.

Dave.

I have a saito 80 on an extra 300 can't stand the thing so I am going to put a ys 91 on. The saito will be on the bench for a while.

Finally seemed to have solved the problem. Looking at the low speed needle valve, when leaned properly it actually was sticking into the spray bar a short way. After filing about 1/2 mm off of the low speed needle valve in the shape of a point at about a 45 degree angle the engine is now a *****cat, transitions and idles perfectly. Since I had nothing else to use I did this by inserting the needle valve into a hand drill and spun it on 220 wet/dry sandpaper with a little oil. All on the same 13-8 prop, which by the way is one of the suggested props listed in the Saito manual accompanying the engine. Since I had already replaced this engine in my 4*60 with an OS91 I will be using it in a Sig Hog Bipe under construction in, hopefully, the near future.