Evolution .46 troubles
 

I seem to be having some troubles with the Evolution engine on my Alpha 40 (RTF). First, you all should know the modifications I've done incase it makes a difference. My trainer wanted more leway on the needle adjustments, so I removed the set pins from both the high and low speed needle valves, I also removed the flywheel from the prop driver so I could run a two bladed prop/hub.

Now for my problem. When it's at max throttle everything is great. When you pinch the fuel line, it increases in RPM slightly and everything sounds good The problem is, it sometimes has trouble getting up to high speed when it's been at idle for a little while. The guys at the field are saying that it "loads up" too much. After I taxi it out on the runway and try to apply full throttle, it will stumble and struggle to get to max RPM. It does the same thing if I make a slow speed pass over the runway and then apply full throttle. It takes forever for it to get there. It's definitely making take-offs a little scarier than they need to be.

We messed around with it a bit at the field, and according to my manual my problem indicates that the low-speed needle valve is too rich. However, we tried leaning it all the way out at the field (all the way clockwise) and it still has the problem. When the plane is on the stand, it sounds like it's idleling fine, and if you continually rev it, the engine seems to do fine. It's only when I have it at low RPM for a while that this problem occurs.

Ideas on what to try next?

RE: Evolution .46 troubles
 

dont know anything about 2strokes. im a 4 stroker but it sounds like youre not geting presher to the tank. make sure there is no kinks in the line and it fits good. you may want to try puting a check valve in the presher line.

RE: Evolution .46 troubles
 

It certianly sounds like the idle is rich. Try doing the pinch test at a idle and see what it does. But if u leaned it out ALL the way.. Hmm.
-John

RE: Evolution .46 troubles
 

This info comes straight from the MFGR:

Open the carb 1 millimeter

Close the low-end needle

Open the low-end needle 1 1/5 (One and one fifth) turns.

That is where it is SUPPOSED to be set at the factory, but a few slip by that are not set correctly

RE: Evolution .46 troubles
 

Try it without a muffler and see if raw fuel is spitting out at idle. If it's just oil and no smell of raw fuel i'de go with the tank pressure checks and make sure the tank is level with the carb body as per instructions. 1 more thing u might check is the plug change it with a known good 1 and make sure it's the 1 recomended, and the compression.

RE: Evolution .46 troubles
 

When you adjusted the low speed needle, did you readjust the High Speed Needle? A fully leaned out low speed needle should stall at idle. To properly set the low speed needle, you MUST readjust the high speed needle before trying the transition test. If you fully leaned out the low speed, then your running totally on the high speed needle, and your high end is probably VERY rich. You'll need to richen up the low speed needle and lean out the high speed needle to get back into the operating range. One way to accomplish this is to do the following:

With the engine OFF, set the throttle open about the width of a needle. Now attach a clean piece of fuel tubing to the fuel inlet. Blow through the tubing. With the low speed needle fully leaned out, you should not hear any air hissing through the carb. Now slowly back out the low speed needle until you begin to hear air hissing. This is close.

Start the engine, full throttle, set the high speed needle to peak RPM less 300 rpm to the rich side. If you have access to a tachometer, use it to adjust your settings. Now perform the transition test. Use the results to make low speed needle adjustments in increments of 1/8 turn or less, and reset the high speed needle valve before trying again. Keep making small adjustments until the engine transitions smoothly with no hesitation.

Good Luck!
Brad

RE: Evolution .46 troubles
 

I had a similar problem with my Evolution motor - finally gave up and called Horizon Hobby's support line and they had me send the motor into them. They said that the carburator was bad, but since they didn't have any in stock, they just replaced the whole motor. Never had a problem with it since.