The Evolution engines all like to load up with unburned fuel. This seems to be the same from the .40 Alpha up to the .61. The 1.00 seems to do that but not many reports on RCU about it.

The one thing that these engines need are plugs hotter than the OS 8. Have you tried this yet?

I have heard that before too. Worth considering.

A3 plug, Rossi 3,4, McCoy-56/59, OS-F is sometimes a good alternative - hot plug with a protected element.

My Evo .46 surged also. Adjusted needles, changed plugs, tried everything.

Found a leak in the fuel tank at the stopper. Fixed leak; problem solved.

You don't have to pull the tank to check for leak. Pull the lines off the carb & muffler nipple, plug the carb line & suck on the pressure line. After 5 or 6 sucks, stick the end of your tongue in the line to block it. You should feel a vacuum trying to pull your tongue into the line. If not; you got a leak.

Shack

I did not read every post, but I scanned them real quick. I did not see that anybody had this suggestion. I had a .61 that gave me trouble for a year. It stayed nasty all the time I could clean it real good and fly one day and it looked like it had never been cleaned. It ran good for about a year. Then it got where it was untunable. It ran (to the best of my memory) as you are describing. I bought it straight from horizon hobby, but did not save my sales slip. When I moved back home I became friends with the LHS owner. He gave me a receipt for around the same time I bought the engine. I returned it to Horizon for repair. They sent me a new one and told me that there was a hole in the case somewhere. Even though I could not see it. They said it was very small.

If you could get a receipt (if you don't have one already) and return it to Horizon I bet you will find out yours has a small hole somewhere in it.

My new one ran fine by the way.

Good luck and let us know what you find out.
Alan

good call....

A flaw in the casting would cause the issue, and drive you nuts. Not something one typically looks for.

Something like loose fasteners on the backplate can cause something simlar too.

Often the effect is not seen until the engine warms up, or is running at power (pressure) where conditions cause the leak to get worse

You can get small cracks that are nearly impossible to see if the engine hits hard. They are around the mounting tabs a lot of times. They will never run well or predictably when this happens. Sometimes, you will find the cracks around the carb mount too.

Spiral72,

I solved the vent line plugging problem I was having by removing the muffler baffle plate. Horizon had said the engine ran fine after we sent it in, but the line plugged itself within 10 seconds of running full throttle. Removing the muffle baffle solved the problem.

http://www.rcuniverse.com/forum/m_68...tm.htm#6992949


I hope this might be helpful.

--Doug

Spiral

I have gone through all the problems you are having with a second hand Magnum 40 that I bought from a club member. It was a two year old engine. When I flew it on a new trainer it was surging in flight so I would tune it for optimum performance before flying and it would run good for 2 flights then sputter, surge, and sometimes die. Tried most all things you did while I had to wait for the O-RINGS I had ordered for the low and high speed needles. I had suspected this early on but the o-rings were backordered for some time. Once they came in and were installed the problems went away and the Magnum ran like a new toy. Still running it a year later. Hope this helps you.

Steve