jolin

got a problem with an evolution 46 engine. On the ground it will run at full throttle about 10 seconds and then start slowing down. If I let it go it wil eventually stop sometimes and then sometimes it will pick back up. If I reduce it to half throttle it will run fine. The idle is fine and maintains a constant idle at about 2500rpns. The transition from idle to full throttle is fine. In the air it does the same thing. I have tried richening and leaning the high speed needle to no avail. Using the pinch test the RPM increases before stoping which would indicate to me the high speed setting is OK.

Any thoughts as to what the problem is. I've had two dead sticks landings and don't want any more.

tailskid

My Feedback: (34)

When doing the pinch test, your engine should speed up momentarily, BUT THEN KEEP RUNNING!

Jerry

w8ye

My Feedback: (16)

Do your pinch test the way you normally do with your original assumptions, but, do it when the engine starts to slow down.

Seems to be going lean.

May possibly be getting hot?

Enjoy,

Jim

2slow2matter

My Feedback: (1)

How could the engine keep running, if the fuel supply is pinched off?

How I always do the pinch test is to test the low speed needle. Run the engine up to clear the suds, then back to idle. after a second or two, perform the pinch test. Should idle up, then eventually die--given you don't let go of the fuel line first!

High speed needle should be not as tricky to set. Run it up and adjust it until it runs at peak, then back off about 200 or 300 RPMs and go fly. Sounds to me also like it's going lean. Could be a bubbling problem. Is your fuel foaming? Are there bubbles in the fuel supply line before it quits? This will cause a leaning effect, and cause the engine to die. Sometimes this is more pronounced at high throttle settings, because of the harmonics of the engine. Make sure your tank is well padded, and there is no foaming or bubbling of the fuel. Other than that, it is probably still a tuning problem.

tychoc

I had a similar problem, and for me it turned out to be a leak between the engine and the muffler. Once the engine reved up, the back pressure from the muffler escaped around the gasket and the engine didn't get enouth fuel at full throttle due to the loss of muffler pressure to the tank. I used red silicon to seal the muffler well, and the problem went away.

Worth checking into.

-tychoc

MrMotor

Check the fuel line between the remote needle and the carb or move the high needle onto the carb and eliminate the extra fuel line.

jolin

I may have stumbled onto my problem. I noticed some fuel leakage around the throttle barrel and throttle arm. When I took the throttle barrel out of the carburetor body I noticed from the blowup of the engine parts that there was supposed to be a throttle barrel spring that keeps play out of the horizonal movement of the barrel. There was no spring in between the throttle barrel and the carburetor body. I have ordered a new spring to take the play out of the barrel and hopefully that will take care of my problem.

I think it is a fuel starvation problem rather than air leaks. I'm not seeing any bubbles in the fuel line.

blw

My Feedback: (3)

That's good then. However, think about doing what MrMotor suggests once you get it running. I have 2 Evo engines and both had leaks in this area with the factory fuel tubing.

By the way, what fuel and glow plug are you using?

w8ye

My Feedback: (16)

When the barrel spring is missing, the mixture will change on you suddenly causing the engine to change speed.

Enjoy,

Jim

LuckyArmpit

Also keep on the lookout for this problem. I have the evo .46 in my Sig Kougar. After flying a while, decided to get her down into the landing pattern. Backed off on the throttle. But, throttle still seemed too high. Flew around a bit and tried again with same problem, it wouldn't throttle down. Landed it that way. It was a fast landing!!!! Problem is that the barrel wouldn't close. It would get to 1/3 closed and would not move any more. Even if you pushed the arm by hand, wouldn't completely close. Called Horizon. The guy I talked to said they have never seen that problem. They sent me a new carb. Glad because new carb is $36.

Dave...

paradise

Funny, I have one and I have a very similar problem. That low speed adjustment mechanism does not hold its position well....I think its sucks and I think that is where my problem stems from. Too bad. They are supposed to be nice engines. Mine is gone.

JustB

I had a similar issue, I could not get my 3 month old Evo .46 to rev above half throttle without dying, first thing I did was change the glow plug to an OS#8, The problem changed so I could rev up but it would not peak and kept "hunting" just would not rev up smoothly or predictably, I then compared the 2 glow plugs and found the original to be longer, I then tried the OS four stroke plug and Problem solved!!

Motor now peaks and transitions smoothly from idle to full and back.

A new problem is my exhaust muffler through nolt's head has sheared off and it seems impossible to get this separately.

Hope this helps.

blw

My Feedback: (3)

Look at it this way, a new carb for a .46AX would have cost you $51.99!!!

travwhit

Get you a 2 ounce bottle of versachem lion gasket shellac and seal the back cover, and muffler with gaskets plus this. It is easier and cleaner to paint this on with an artist brush instead of the one that comes with the stuff, but be sure you shellac the gasket to the muffler and let dry a few minutes before you paint the engine and other side of the gasket. when I take the muffler off now, (with a slight bump to unseat) the gasket stays intact and all I have to do is reapply the shellac. I had a Tower Hobbies .46 going bonkers with me and I did this, now it is happy and I am turning an 11X7 prop 11,500 RPM with unlimited vertical on 15% Wildcat! Super transition with maybe just a little rich at 3/8 throttle, but Idle, 1/4, 1/2 to WOT is fine. These overbored engines are a little tempramental if everything is not just as the designers intended, but if they are right they will spin a 11X7 or 12X4 prop with unlimited vertical.

Trav

speedair

I took the bafle out of mine and the engine run ok then. Also check to make sure there are no leaks between the engine and mufler

BlavkskylineR34

OMG I LOVE YOu this fixed my problem!

tyallen

its a leak somewhere. its either your exhaust is loose or there is a bad connection/hole in your fuel line or tank. i had a similar issue and thats what it was. also you might need to tune the low end needle. i searched online and found out how to do it and mine throttles up quickly now and runs great!

blw

My Feedback: (3)

This is a 2 year old thread, but many people don't realize that the low speed needle is usually the most important adjustment on 2 strokes just like 4 strokes.