I am currently trying to get a Super Custom 56 to throttle correctly. I have set up the fast running needle for max revs and now am trying to get the secondary needle adjusted so that it will throttle up smoothly from a fast idle.

What is the correct procedure for doing this? Should I start from it being open X turns and then start closing it down 1/4 turns at a go? or is there a better way of doing this?

Thanks in advance

Ron, if it will idle now that's a good place to start. Keep in mind the low end is a little harder to set. The reason
is you don't get imediate results as it takes longer to burn the fuel out of the crankcase at idle. So make small
adjustments and wait 15 seconds between each one. First try and figure out if your rich or lean.
If it is rich it should lose RPM when you take the power sorce off the glow plug. It will then pick up
RPM when the hot shot is reattached. If it is lean it will die soon after it starts and get hot after two or three attempts. I am going to assume it's rich. Most are, as the factory sets them rich for breakin. All you need to do
is close the needle 1/8 turn at a time untill it will idle without the hot shot and without getting overheated.
It should idle several minutes with no problems. Make sure you kill the engine while adjusting.
If you can get it to idle without getting hot and without the hot shot changing the idle you should be
right on. Try this and let us know what happends. later daveo

OK,

I've got an engine (OS .46FX) that idles quite well with no noticeable drop-off when the glow-plug power is disconnected, has decent top-end, but stutters badly and occasionally dies in transition if you just jam the throttle on. I know I've read the description for how do do this adjustment, but I can't find it.
Any help?

Kfarlee

You may be a little lean on the low speed needle valve, try opening it 1/4 turn at a time until it will transition from idle to full power.

Jerry

Jerry,
If your RPM drops off when you remove the glow driver you are ready for a new plug. The platinum oxidizes and interferes with the catalytic action between the platinum and alcohol.

Kfarlee,

I just bought an O.S. 46FX too. Mine does the same thing. The manual tells you how to determine if you're rich (white smoke comes pouring out once the engine clears out) or lean (absense of smoke altogether). Mine is rich and I need to adjust it also. I thought I'd wait till I have run it for a while so it's through it's break-in period. One thing that bothers me is that the engine could quit if I hit the throttle to hard while I'm flying, and then may have to make a bad landing. It hasn't happened yet but it could. The next time I fly, I'm going to lean out the mix just 1/8 of a turn and see if it improves. O.S. is being safe with their settings but it could take out my plane instead of their engine.

Again, the manual has the instructions to set this. I agree with the guy who said to wait a long time between adjustments. Very good advice. It could get way out of wack doing one after another. Mine is pretty close but needs an adjustment.

Make one adjustment at a time. If you make two together you won't know which one caused the problem. Start from scratch with the owners manual. The people that make the engine usually, but not always, know best.

Yeah and even if the manual isn't right, if you don't follow it, they can void the warrantee. I followed what O.S. said for run-in. I also followed the rest of it (leave the engine rich for 4-6 flights). Gradually make it less rich after a bunch of flights. It runs great. Also I adjusted the mixture like they said and was perfect. I think their manual is pretty good (46FX).

I’m not familiar with a Super Custom 56, but here is a typical procedure that works for most two strokes.

To set the high speed needle, start the engine with a fairly rich setting. Open the throttle all the way. Lean the mixture until the RPM peaks and begins to drop off. (If you go too far and the engine quits, back out the needle about ½ turn and restart.) Peak the RPM and back off a little. You want the high speed setting to be a little rich of peak.

To set the idle mixture, retard the throttle until the engine is operating as slow as it will idle, which may be pretty fast if the adjustment is very far off. Pinch off the fuel line. If the engine dies suddenly, the idle mixture is set too lean. Richen the idle mixture and repeat. If the engine gives a burst of speed before it quits it is rich. Lean the mixture a little and repeat. As you approach the proper mixture, the engine can be set to a lower idle without stopping. As the idle speed is reduced, repeat the procedure until when the fuel line is pinched off at idle, there is a slight increase in RPM before the engine dies. The final test is if the engine accelerates smoothly from idle to full throttle.

There are two types of idle mixture adjustments. One adjusts the fuel flow and is generally a small needle with a screwdriver adjustment opposite the high speed needle and centered in the throttle arm. The other adjusts airflow through a bleed hole and can be located on the throttle body. The needle type turns clockwise to lean while the bleed type turns counterclockwise to lean. If you think the engine is badly out of adjustment, you can get in the ballpark as follows. If it is a needle type adjustment, attach a line to the fuel inlet and close the throttle completely. Blow gently through the line and close the idle mixture adjustment until you can’t blow, then open it a little. If it is a bleed type, look in the hole and adjust the screw until the end of the screw covers half the hole. These procedures will get you to a good starting point.

After you have made these adjustments, with the throttle wide open, raise the nose of the plane vertical. If the RPM sags, richen the high speed needle until it runs smoothly then just a tad more. The nose up attitude lowers the tank well below the intake and tends to lean the mixture. As the tank empties it will lean it a little more. It probably won’t be necessary to change the idle mixture.

Finally, don’t expect to get a dependable idle down too low. Somewhere on the order of 2000-2500 rpm is reasonable.