SkyPilot101

It does sound like a fuel delivery problem, is your tank mounted in the stock location behind the firewall, or did you move it back toward the C/G? Those small evolution engines don't have a fuel pump, and have to be set up on muffler pressure, just like a glow job. Thinking of that, how's you muffler to tank pressure line?

bayfield16

My Feedback: (2)

The tank is located just behind the firewall in the stock location. I had a pitts style muffler on the plane at first but put on the stock muffler to see if the pressure to the tank was the culprit. There was no change in the behavior. The engine is mounted 90 degrees to the right. I have tried turning the plane so the head is straight up with no change in the problem. The tank outlet lines are directly in line with the carb. My initial guess was the regulator but with a new carb comes a new regulator. I also pressure checked the fuel system with no leaks. The crazy thing is that it runs great when the plane is level. Revs up when pointed up and stalls when pointed down. Double checked the clunk etc. By the way the change in engine rpm starts as soon as I start nosing up or down, no hesitation. Thanks for the thoughts. I may take the engine out and mount it on a test stand with a different tank to see what happens.

cymaz

Thanks for that, I'd be very grateful

ahicks

My Feedback: (2)

Bayfield, have you tried going back to the starting carb settings, especially the low speed, using the procedure in the owners manual?

AA5BY

Bayfield.... are you certain that the tank is secure and not shifting forward when pointed down and in the process pinching of either the pressure or fuel feed line?

AA5BY

I will try to get some measurements tomorrow.

bayfield16

My Feedback: (2)

Thanks AA5BY and ahicks for the ideas. I did reset the low end as the manual instructs with no change. I think I will start "playing" with the low speed needle to see what happens. The tank nose goes into the hole in the firewall, is mounted on foam with velcro holding it in place. I also built a bracket at the rear of the tank to keep it in place. I also took the regulator apart to see if the little piston was moving easily, it is. I agree that it seems to be a fuel delivery issue but just haven't been able to trace it. My next step will be to put it on a test stand. Thanks again for the thoughts...

josephcraig

Bayfield16,

Was you able to get your 15cc figured out?

bayfield16

My Feedback: (2)

I've put it aside for the time being. I have a new tank and will try that next. Thanks

josephcraig

I have several gallons through my 15cc.I never tried the nose down test.Always up test..Sullivin makes a really good stopper kit with allen screw.Thats what i use plus two plastic tie straps on each fuel line.Fuel problems was a pain for me on the 10cc.I had ordered a gas stopper and it was labeled as gas stopper,but it wasn't.You know what happened next.

JoeyCoates

I have a question for you guys. I am going to put either the 10cc or 15cc engine on a Sig Kadet Senior that currently has a RCV60 on it right now. While the RCV is a neat engine, it really does not have a lot of go at all, and flying the Kadet off water is pretty sketchy right now. It will do it, but not by a whole lot and if the water is smooth (calm wind) I have to work it to break suction and get in the air. So with this being said, I have been leaning towards the 15cc as there should be ample power, but would the 10cc be enough? I am not trying to have unlimited vertical or anything like that, it is a relaxing flyer, but I certainly to not want to replace one power deficient engine with another! I think it has a 10oz tank in it right now which would be replaced and plumbed for gas, and I believe the weight is similar for a whole kit 15cc and the RCV as the RCV is kind of portly. What do you guys say?

cymaz

15cc. Having not flown off water. Think of flying it as throttle management with a slightly bigger engine. You won't regret it.

bayfield16

My Feedback: (2)

Well I put on a new tank and still have the same problem with the Evo 15cc gas engine. I spent an hour on the phone with Horizon and they suggested all the things I have already tried. Bottom line, it was an experiment to go that small on a gas engine and I've given up on the engine.

josephcraig

I'm sorry you have had these problems with the engine.I'm curious..Have you flown the engine yet,cause I never have lifted the nose on my plane before.If you have a good flying field,I would fly it on level flight and keep it high altitude until broken in.

drose1644

Need help! I have an Evolution 15gx, using a 13x6 break-in prop, with 20:1 fuel. I broke it in on the ground, per the manual; then went to the field for it's first flight. Hard to get my .52 size Pawnee Piper off the ground, RPMs only about 8,150. Got a lot of advice from the field, came home and tried several things. Going to 25:1 fuel mixture only added about 100 RPMs. I did put a Pitts style muffler on, which took it up to 8,800. I was using a .65 size torpedo style; I can't fit the larger muffler that came with the engine. Very curious how the muffler can make that much difference. All three (original, Pitts, & smaller torpedo) have the exact same outlet size, as measured with my micrometer. Also, I started my fuel adjustment at the 1 & 1/4 turns out, per the manual, but it tunes out at about 1/4 turn out. And while it starts great at that setting when hot; you have to open it back up to at least 1 turn out in order to start it cold. I really need to get much further up to 10,000 RPMs in order to get enough torque; any ideas??? Donnie

josephcraig

Have you tried changing your low side needle both ways?

drose1644

No; the indications in the manual representing a need to go more lean/rich with the low speed, aren't evident. I'll try that, can't harm!

drose1644

Pete, not sure if you saw this post; I misplaced it under another sub-thread. Sure hope you can help. I have an Evolution 15gx, using a 13x6 break-in prop, with 20:1 fuel. I broke it in on the ground, per the manual; then went to the field for it's first flight. Hard to get my .52 size Pawnee Piper off the ground, RPMs only about 8,150. Got a lot of advice from the field, came home and tried several things. Going to 25:1 fuel mixture only added about 100 RPMs. I did put a Pitts style muffler on, which took it up to 8,800. I was using a .65 size torpedo style; I can't fit the larger muffler that came with the engine. Very curious how the muffler can make that much difference. All three (original, Pitts, & smaller torpedo) have the exact same outlet size, as measured with my micrometer. Also, I started my fuel adjustment at the 1 & 1/4 turns out, per the manual, but it tunes out at about 1/4 turn out. And while it starts great at that setting when hot; you have to open it back up to at least 1 turn out in order to start it cold. I really need to get much further up to 10,000 RPMs in order to get enough torque; any ideas??? Donnie

josephcraig

Donnie,
Go back couple of pages on the this forum and click his name and private message will come up.You can send him a private message and it may get him quicker..

josephcraig

Donnie,
Was you able to get rpms up?

hessian123

Does anyone have experience with the new 15 and 20cc engines with Pumper carbs? I have one of the 20GX2 and I'm not sure what to do with the pressure port on the muffler. I thought with the pump I wouldn't have to pressurize the tank.

Dooz

There's a line that runs from your tank to the carb (fuel inlet), then one that runs from the carb to the crankcase (is that the one you mean?). If that's the one, your Viton should run from the carb to the crankcase (around the "E" of evolution).

hessian123

No, actually, there is a fuel barb on the muffler, just like you'd see on a glow muffler. The crankcase port was already connected to the Carb with tubing when I received it. Maybe I'll just try plugging the port with some jb weld.

jspauld2

Hessian,

You are correct in that you do not need to use the port on the muffler. We included the port on the muffler in case you wanted to run a smoke system with this engine. You can plug the port if you do not plan on using it.

Jimmy

hessian123

Thanks Jimmy. You guys may want to amend the manual to say something about this.