Your problem is impatience! There are probably multiple settings that are not quite right, and your inexperience is causing you to chase the problems. You need a methodical approach to tuning that an experienced ear will really help you get through. Get your hands on a tachometer to make this easier.

New motor, new glow plug, new fuel, you can probably rule those out as problems.

First, get the motor running, and with the glow igniter attached, get it up to full throttle. Now remove the igniter, and adjust the HIGH speed needle for peak RPM and then back it back out (richen the mixture) until the RPM drops about 300-500 RPM.

Now that the motor is up to temperature, and the high speed needle is set, bring the throttle back down, and adjust your THROTTLE trim to about 3000 rpm.

Now allow the motor to sit at idle for about 30 seconds. Now pinch the fuel inlet line and listen carefully to the engine. If the engine rpms rise slightly, your low speed needle setting is slightly RICH. If the engine just dies, the low speed needle is lean. Release the fuel line before the engine stalls. Slowly raise the throttle to full for a few seconds to clear things out and warm it back up, then bring it back to idle. Let it set for another 20-30 seconds at idle, then punch the throttle to full. If the engine hesitates then goes to full throttle, the LOW speed mixture is RICH. If the engine sputters and dies, the LOW speed mixtures is probably LEAN. If these two tests give you inconclusive results, just guess if its rich or lean.

Now, turn the engine off by putting your finger over the carb inlet or the kill switch on your radio (don't use the throttle trim yet).

With the engine off, make a SMALL adjustment in the LOW speed mixture screw (its the one inside the throttle arm). The adjustment should be 1/8 turn or less. Its very easy to completely miss the optimum setting if you make to large a change.

Now restart the engine, and (this is important) reset the HIGH speed needle for peak RPM and richen to 300-500 RPM below peak. Did I mention this is important? Now repeat the tests as before. Is the engine behaving better or worse? If its better, keep making adjustments in the same direction until the engine will go from idle to full throttle without hesitation. If you cant tell if its better or worse, keep making adjustments in the same direction until you can tell.

The key is to make only one adjustment at a time, and then see how its performing. The good news is that once you have the low speed needle set, you probably won't have to touch it ever again.

Good Luck

Brad

dangerous act placing finger over a carb with the engine running maybe bkdavy don't like his fingers

Run it with the glow driver on if you have to.
You want to run several tanks through the engine on the ground to break it in.

One of the first things I did was to toss the limiter thing into my flite box. It was set wrong!
Then try to set up the mixture, the engine needs to be broken in, mine needed to be.
One of the first things I did was to toss the limiter thing into my flite box.

Don't sweat making it purr it will. If you can not lean the engine with the set screw inside the throttle barrel I have a few things for you to check.
Check that you are getting full throw from you servo, full open full closed. If you are and still cannot lean the low end very slowly
crank you cleavis adjustment so you open the throttle just a hair. Then set the screw to closed Make sure that the screw you are turning is inside the throttle not the one above it that is the retainer high-end stop.

Do not under any circumstances try to adjust you low end with the engine running you will lose a finger it is to close to a prop!
If you want to stop the engine just pinch the fuel line make your adjustment then restart. It is a pain but you will get it with some practice.

Well, it turns out the most simple solution is the one that worked. I tried all sorts of things in the beginning and started trying to adjust the low end needle and just made things worse. Then I received a call from Bill, a.k.a. 'the_madgenius' who led me through a series of instructions on how to get this engine performing how it should. Well let me tell you, I followed his instructions and it was actually quite easy to fix.

First I returned the low speed needle to it's original position. Then I closed the high speed needle fully, then opened it 2 and a half turns. I started the engine, opened the throttle up and tried to get it up to full throttle. It was still running quite rough and coughing and spluttering and it took the engine a while to increase in speed. With throttle open completely I then started slowly closing the high speed needle. Immediately I could hear and feel improvement. As I kept closing it gradually, the RPM was increasing and at the same time it was starting to run a lot smoother. Previous to this Bill also explained to me how to listen out for the change between four cycle and two cycle. Eventually I could hear it starting to kick in to two cycle and the improvement was phenomenal. It was actually running normal! No vibration, no more symptoms that I previously mentioned, and it sounded great! Anyway I started to listen out for peak RPM, then went back the other way just a fraction.

What I get now:

The idle is smooth and slow without shaking. It throttles up really well. There's no fluctuation in RPM. And, its very very responsive which feels great!

The only problem I'm having now is the top 1/4 or so of the throttle does nothing. But from idle up to 3/4 throttle it is perfect. After that when I open the throttle fully I don't see any more difference. I'm guessing it just needs a little bit more tuning - that part I couldn't get perfect but I might leave that to the pro's next week. For now the best part for me is that the problems I was having before are gone and it now sounds and feels like a normal engine.

The difference is huge compared to how it was running before. Also the problem I was having when i removed the glow starter is gone. There's no difference when I take it off, it still runs the same.

Thanks Bill you are a legend, I followed your instructions and got the result I wanted.

And also thanks to everyone else here who has helped me, I've learnt heaps from this!!

You guys are great!

Chris.

No more dangerous than trying to adjust the high speed needle with the engine running. Approach from behind the engine. This is a good way to cut the engine, particularly when you're trying to tune it. I prefer the throttle cut switch on the transmitter, which doesn't affect the idle trim, but if you don't have that option, covering the carb works quite effectively. Once you have the engine tuned, you can go back to using the idle trim switch.


Do you mean 3/4 throttle on your transmitter? I suspect you do. The throttle servo is probably forcing the barrel into the stops at 3/4 travel. This can normally be adjusted by the "end point" adjustment on your transmitter (if it has one). It might also be referred to as the "volume' in the transmitter manual. Adjust it until the full throttle position on the transmitter just pushes the throttle barrel against the stop. Improperly adjusting this setting could lead to premature servo failure, and unnecessary drain on your battery as the servo tries to force the control arm against the stop.

Brad

you don't tell a learner to choke the motor it is a dangerous practice.if he can't adjust the high speed needle he should get a experience person to do it

Yeah I've kinda figured out I don't want to get my hand that close to the prop. The high speed needle is close enough for me, for now at least. Thanks for your concern davo.

no worries I kind of thought that you like your fingers

I beleive the correct way to turn off the engine is to pinch the fuel line before it reaches the carb. If you are at idle it may take a few seconds. That way you don't have to count your digits and pray that you still have them all.

very true

I'll have to say that I have had my stupid moments. When I got my start in aircraft modeling, control line, to stop a Cox .049 you threw a rag into the prop. No fuel line to pinch. Then I got a Fox .35 stunt. First time I tried to start it with fingers. The prop came around and bit me. It hurt enough that I used a screwdriver handle from then on. I didn't have anyone to talk to about the hobby so I learned averything the hard way. Once I had the engine running and was watching dirt going up the fuel line toward the carb. Without thinking I stuck the screwdriver in the prop. The prop survived, I got away with a few scratches, and it hurt like hell. I didn't think to either pinch the fuel line, or to pull it off the carb, but knew it was way too close to stick my finger between the cylinder and prop.

If the throttle body still moves from 3/4 to full don't worry too much about there not being much more power after the 3/4 mark because when you get to that point the engine throttle response is not linear

which means?