I have the .61 evo and everything is fine except the engine idle,it is way too fast.Do i slow engine speed down with the black set screw on top of the carberator ?.
Thanks

The black screw on that engine just holds the carb togehter really... it CAN limit how far the carb barrel can close, but if its set correctly it will allow the barrel to fully close which shuts the engine off. (and thus that screw SHOULD not limit how low the idle can be)

The screw you have LABELED as the idle adjustment is where you adjust the idle... Hmm... should be obvious.

It is possible for hte stops built on that carb to be preventig you from adjusting for best idle... But with the adjustment centered between the stops... you should be able to make it idle better.

Most engines will refuse to have a stable low speed idle until they have been "broken in" some. give it several tanks to a couple of gallons of fuel useage before you worry too much about getting the low speed idle adjusted "perfectly." (its never perfect on a 2-stroke... you have to tweak it a bit with weather changes.)

I loosened the allen screw on the blue collar and turned the screw but it didn't seem to make any difference,i set it back to it's original place.I overlooked something,the screw on the servo might of slipped but i can change the idle that way,the engine is running too fast to adjust the low speed but with the tx i can slow it down enough to almost count each point on the prop,well not that slow but it runs pretty smooth,i can still kill the engine that way.
Thanks

* no way am i gonna turn that screw unless i know what it does*

Sounds like you are [:@]PURPOSEFULLY [:@]trying to adjuste ANYTHING EXCEPT the correct (properly labeled on your own picture[>:]) thing for adjusting the idle.

By this time you should have the adjustmends so far out that the engine maker's factory rep would have problems.[:'(]

I'm done.

When i get it all whacked out of adjustment ,i'll take it down and let you adjust it.
j/k

It sounds to me like you're just not closing the carb enough. You should be able to close the carb to the point where the engine runs so slowly that it will quit. The idle adjustment screw has very little to do with RPM, it is a mixture control, not an RPM control.

Well it's good to see you randomly crap on everybody not just me.

I have no idea where your town is... if its reasonably close... bring the plane to the Temple Modeler's Airfield, outside Moffat, TX (on hywy 36, 11 mi from I-35) on Wed after 4:00pm (any wed.) I'll probably have it adjusted correctly within 5 min.

(still making too many typos...[&:])

As Minn said, the small screw with the arrow pointing to it is the idle mixure screw, not idle speed screw.

If the engine idles reliabliy and transitions well, then it's fine, don't mess with it. From your question, I'd say leave this one (and the limiter device) alone, it's not your "problem" at all.

However, if you can't get the idle speed down slow enough, the black unlabaled screw in the picture will often stop the barrel from closing all the way.

Here's how to check. Disconnect the throttle linkage from the carb. Now, try to close the throttle with your fingers (engine NOT running here, btw). Look down the carb throad. Is the barrel fully closed? Or did the throttle arm hit against something that prevents the barrel from closing all the way?

If the barrel can not close all the way, back out the black unlabeled screw just a little bit. Now try to close the barrel again. If the throttle arm moves freely, and the barrel can be fully closed, you've got it right.

Note: some carbs have two screws on top, like in the picture I'm attaching. I don't think the Evo carb is like this. But if you do have a second screw up top that isn't visible in your picture, the screw you can't see is the one you want, and the black one in the picture just holds the barel in the carb. If you only have 1 screw up top, then it's a combination screw that both limits the carb travel on the low end, and prevents the barrel from falling out. OS carbs (at least the old ones) use a combination screw like this. I think the Evo is like this too.

Ok, so if you can close the barrel all the way with out the throttle hooked up, now hook up your throttle servo and check the movement the servo gives it. When the throttle trim in the full down position, and the stick full down, the barrel should be totally closed. If it's not, adjust the linkage (or ATV/End points/servo travel on the TX if you have it) until the throttle does close. Now move the trim to the full up position, with the stick still full down. The barrel should open enough for a solid idle that will be good for acrobatics and such. Somewhere in between will usually be your lowest idle that the engine will run at.

Also, keep in mind that new engines don't idle as well as ones that are well broken in. And smaller engines don't usually idle as well as larger ones. So you shouldn't expect a new .46-.61 to idle much below 2krpm out of the box.

forgot the picture.

I just lifed this picture from Horizon's web site. There is only one screw up on top of the carb. That screw, the black one, will both hold the barrel in the carb and limit the barrel travel. You'll want to back this screw out just a hair until the barrel can be closed fully.

I guess I have been doing it wrong all these years, I've always adjusted the idle RPM with the throttle trim on my tx. Silly me![X(]

Yes, once the engine and airplane are set up to allow that to happen, that is how you do it. But some engines do (or did) come out of the box with the throttle stop screw set so that the servo (or your finger or anything) could not move the throttle barrel all the way closed. So you could wiggle the stick or the trim lever all you wanted, all you'd get is a stalled servo, the engine would not cut off or idle below a certain point because the carb would not close enough.

And that's why i said i would take it to you but it's almost impossible to take it down on wed as i live east of Dallas on IH 30 ,by the time i got there it would probably be dark,say,wanna install some lights for flyiing at night ?.One day i'll go down and buy you a drink (coke but not spirits) and i'll let you fly it,AT NO CHARGE,after you adjust the carb ,tomorrow i think i'm going to a swap meet as i need to buy something,have no idea what but........

Sunday... (this Sunday) appx 12:30 to dark I'll be at the field. (I expect dark about 8:00 pm)

The club pot-luck picknick is at 1:00. Combat competition (club rules... club members only) will have thier rounds spaced between other flying from about 2:00 to 3:30. Open field aside from durring combat rounds. (flying is allowed while others eat... but its not recommended that you eat and fly at the same time. )

http://home.hot.rr.com/taeromodelers/aero1.html there is a map to the field on the site.

Put a little beer in the tank. That engine will run like a dream. O WAIT! I said that wrong.

Put a little beer in YOUR tank and you'll dream about a good running engine.

Is that the reason you have "crashed a few ?".

Ok,after i readjusted it so the rpm isn't running wild,i done it by adjusting the rod going to the servo,it is much better,what i havn't done is adjust that dreaded black screw since i didn't know what it does.I did the pinch test on both high then low and it's running great again.
What i did find out is if you let the engine run to slow at idle it will stumble while reving it up and yes it's true,they might run perfect today but tomorrow is another thing,maybe sluggish.
Yes you can adjust the idle on the tx with the throttle trim,i do it that way myself,and i can still kill it that way.
It's been raining almost all night,i called the fly-in and it's also been raining but since it's AMA sanctioned,they still have to show up but the swapmeet is probably gone.[]