Okay........I pulled my DA-50 from EF Yak and it was running like a top on a stock muffler. I put it in an EF Extra with a tuned pipe (MTW RE2).

I started it today for the first time and let it idle for about 4 minutes per DA's instructions to seat the teflon coupler between the header and pipe. All was well. I loaded the plane up and headed for the field. When I got to the field the engine would not run more than a couple of seconds at a time and then would die I went all around with the needles trying to get it to run. I got it to run up a little one time but it had no top end (bogging very bad and would not come up) When I transitioned back to the low end it ran until I shut it off to lean the top end. I tried to reset both needles to 1.5 turns out and put a new plug in it with no with no results. When I got home I took the regulator switch and Lion battery out of the picture and bypassed them by hooking a NiMh battery straight to the ignition to make sure it was not any of that. It would hit on choke just like normal. I would turn the choke off and it would start and run for a burst and shut off. The weird thing about the whole thing was sometimes it would start and run for a second or two and then almost like backfire and then run backward.

Gap between header and pipe was set at 1/8th inch per Bill at DA.


Any help would really be appreciated.
Thanks
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It may sound crazy but have you checked to see if the pipe or can is blocked? If it is it will only run until pressure builds up in the pipe. About the time you say this one runs.

Al.....thanks for the response. It appears that the pipe is flowing. You can see that there is smoke coming from the exit stinger on the pipe after the engine fires. There was a few times today that it almost sounded like the timing was off and it would back fire sort of and smoke would really roll out of it. Man my arm and back are tired after that today. I must have turned that prop 1000 times.

Thanks again for the help

You have my deepest sympathy, been there done that. That's about all I can offer buddy as I don't own a DA. Got a DL but that's the only thing that came to mind when I read your post. Sorry, I'm sure the other guys will jump in here and help you out though. If I can come up with any other suggestions I'll be sure and post them.

With oversimplification, your engine only needs three things to run. Compression is easy enough to detect leaving only fuel and spark. Get a new sparkplug and comfirm that is sparking, you could still have a bad ignition module though. Check fuel delivery, you may have to disassemble the carb to look for blockage.

Put your old exhaust system back on and try running the engine again. One would assume the problem is focused on the new pipe system, but this will confirm there nothing else funny going on. Maybe something has failed conicidentally when you changed the exhaust.

Rush

Try rolling the header out of the way, then put the stock muffler back on and see happens.

I do not think the MTW R2 is the culprit. Something else happened along the way.
The pipe is develloped on a DA50, together with DA.
I am currently testing a MVVS 58 with the R2 tuned pipe. The engine previously had run with canisters, but it is still not run in.
Header length 40 cm to start with. running 3W prop 24x10.
No tweaking of needles yet; It started up right away, idle and throttle response rather OK, idle seems rich.
played around with short full throttle bursts for about half a quart.
Refueled with 2.5% oil mix
Started up again, warmed up for a minute, and went to full throttle for rpm measurements. (6150), but engine sagging. returned to idle immediately and stopped engine after a minute.
closed idle needle 1/4 turn, and opened up main needle half a turn.
Idle, and throttle response OK. Warmed up, went to top rpm. 6650, still sagging, so went down to fast idle again.
Subsequent throttle-ups all showed 6650 rpm. I did not wait for the sagging before going back down to fast idle. the engine clearly needs extra running time with the increased power level.
This is to show, that very little tweeking is needed. My engine however is larger, which makes the setup more critical. Your DA should tune sweeter.

Typos edited