CARB ADJUSTMENTS

It is assumed here that if you have a new engine you have already run it at low rpm (4000 maximum) at the rich setting as explained in the instruction manual; this rich low-rpm setting should be used for 15-20 minutes. The final carb mixture settings can then be done as explained below, however 40 - 50 minutes subsequent run time (after the intial 15-20 minutes on a new engine) will probably be necessary to get a final setting with a low idle rpm..

The objective is to get the leanest possible low-speed needle setting such that the engine does not quit when you quickly advance from lowest throttle idle to about 1/2 throttle, and also will not quit when quickly advanced from idle to full throttle. Remember - you are adjusting the fuel mixture setting with the low-speed needle to get reliable operation - you must not consider adjusting the low speed needle to set the low-speed rpm. The value of the idle rpm is set with the throttle stick on your transmitter full back and then adjusting the throttle trim on your transmitter - initially don’t try setting this too low or else the engine may quit because the engine is getting too little of the fuel-air mixture and not because the mixture is wrong. Set the transmitter trim for about 2200-2400 idle rpm speed for a new engine (or whatever value you feel is reliable). After about 40 minutes time on a new engine I can usually get a good reliable idle of about 2100-2300 rpm with some variation between engines; this is enough time on a new engine to carefully begin flying. After 2 or 3 gallons of fuel you should be able to get a new engine to run reliably a bit lower rpm in the 2000 rpm range and still accelerate to full throttle without quitting. However, the throttle and idle performance will depend on your prop, fuel, and how carefully you set it up the needles. Most models will land quite well with an idle rpm in the range 2200-2500 so don’t get too ambitious trying to for a super low idle speed.

From Satio's web site
(b) Low-Speed Mixture: The low-speed needle should already be set about right (ie somewhat rich) for new engines as they come out of the box. If unsure about the initial setting adjust the needle so that the top is flush with the throttle arm level; this is good starting point for all engines except the Saito-30. For the Saito-30 turn the low-speed mixture all the way in, then turn it out 4 1/2 turns; this is a good starting point for that engine.

For the following procedures a tachometer is highly recommended although not absolutely necessary for setting the final carb mixture settings. If it is your first four-stroke engine you should get a tachometer. before you go any further.