Align 91 - Idle Screw

[ZzEther]

Should I touch the idle screw on the 91? My engine needs the trim up quite a ways to stay running. So much that the clutch is engaging a little.

Does it affect the whole range? Is there a reason not to touch it? I've read different opinions. I cleaned my carb today and I'm headed out tomorrow to tune this baby, starting from scratch. Should I start with the idle screw on the bench to get a good idle or skip it?

[ualdrivr]

Most of the time there is no need to adjust the idle screw on the motor, the manufacturer does a good job setting it up. Just set your middle and high needles where they suppose to be and crank her up.

Is your throttle linkage setup right? I would make sure that the mechanical setup is correct.

[ZzEther]

Is your throttle linkage setup right? I would make sure that the mechanical setup is correct.

Throttle linkage is real good, like 95 and 105. Everything is fine but the idle. It won't just sit on the bench and idle all day, it will slowly load up on itself and die. I either have to rush out to the flight line or turn the trim up until the clutch is engaging. Would be nice if it would just sit there purring.

Btw, I don't think it's the clutch, this is the 3rd one in it. My buddy's engine will sit and idle all day and at a much lower RPM than mine. It doesn't load itself up with fuel and die out.

[canbarelyhover]

i would just do the pinch test to make sure your mixture is ballpark, then set the trim to get good idle speed and go fly. remember that idle can act goofy on the first flight of the day until the engine warms up a bit. don't get too hung up on the idle. remember all the fun of tuning is upstairs anyway! :thumbup:

[mystar60]

I would agree with the rest of the posts regarding the stock idle screw setting. Generally you do not have to touch it. Just follow the tuning guide flow chart and ALL needles should end up correctly.

What I would reccomend is to have your throttle end points the same. I would reset them to 100% and then adjust the linkage at high stick as to not bind and full throttle barrel opening.
Check out this post from Ron Lund and it will explain everything more clearly.

http://www.ronlund.com/throttle.htm

Kevin

[ZzEther]

Well thanks for the help guys, I left the idle screw alone. I also installed another .2mm shim in the head. I put the needles back to factory, hooked my carb smart servo to a spare channel so I could tune manually in the air and got to it.

The mid needle is still at factory settings and using the radio to adjust the high needle I got it to where it will almost go UP in rpms when I do a full punch out. But it came down around 225 degrees so I'm going to back off a couple clicks and call it good, or maybe richen the mid needle a click or two. In multiple stationary rolls, where I used to really be able to bog it down, it just drops a tad and stays there, it hangs right with me.

Anyway, she's running beautifully and guess what...it idles! Good call fellas, cya next time.


:noteworthy

[Helico-pteron]

Well thanks for the help guys, I left the idle screw alone. I also installed another .2mm shim in the head. I put the needles back to factory, hooked my carb smart servo to a spare channel so I could tune manually in the air and got to it.

The mid needle is still at factory settings and using the radio to adjust the high needle I got it to where it will almost go UP in rpms when I do a full punch out. But it came down around 225 degrees so I'm going to back off a couple clicks and call it good, or maybe richen the mid needle a click or two. In multiple stationary rolls, where I used to really be able to bog it down, it just drops a tad and stays there, it hangs right with me.

Anyway, she's running beautifully and guess what...it idles! Good call fellas, cya next time.


:noteworthy
You were originally rich and that is why it kept dying. Now you have the high needle leaned out which does change the amount of fuel going to the carb. This in turn allowed you to keep idle at lower RPM.

Now about the mid needle, you are still rich and that motor is still sleeping. I think you may be trying to compensate by leaning the main too much. That speeding up you hear doing punch outs is the carb leaning out, which is bad. So, back off about 4 clicks and start adjusting the mid needle. This is a harder needle to get right, but once it's in the sweet spot,:YeaBaby:.

[ZzEther]

That speeding up you hear doing punch outs is the carb leaning out, which is bad. So, back off about 4 clicks and start adjusting the mid needle. This is a harder needle to get right, but once it's in the sweet spot,:YeaBaby:.

It's not actually going up, it almost feels like it could if it wanted to is more what I was trying to say. The rpms do go down but not a lot and they just lock, no matter what I do to the bird they stay put.

I will take your advice though, if we ever get flyable weather in this state again! I'll back off a little on the main and start coming in on the mid needle and see how she feels, see what the temps look like. Thanks for the input! :Bang