I've got a new DA50 in an Extra 260 and the engine runs for about 2 minutes and then cuts.

It had a total of 10 minutes running time now and every time it dies close to 120 sec into the flight.

The prop spins when the plane is coming down, so it seems that there is NO compression. The compression does return as the engine cools down.

Whats the best way to fix this. Has anybody else heard of this problem before?

Peter

1. run it a little richer
2. go down in pitch size by 2 inches until broken in
3. do you have the recommended oil% in with the gas?
4. cut an air escape hole in the rear of the cowl to allow the hot air out
5. Is the compression OK when the engine is cooled down? if not, take the muffler off and look in the exhaust port, if the piston/ring is scored and grooved where it goes up and down in the exhaust port... send it back to DA

1. The engine is running quite rich.
2. Its only a 22x8 Menz that is on there. If I go down further the engine will rev to high
3. Using 30:1 BP mineral oil, same fuel used in another DA50 setup and runs fine there
4. The cowl has a BIG hole cut in the back. There is plenty of air flow there
5. The compression is good when the engine is cold, just when the engine run it gets very hot.

Peter

If the engine is overheating and losing compression it is running lean.

It could be rich on the low needle and too lean on the high needle.

It's lean. I don't know how many times it has been run this way but the odds are better than average that the ring is history if it has been done a lot.

As Silversurfer says if it's been toasted several times to the point where the prop will windmill round when the motors stopped chances are there will be some ring if nor barrel damage[]

do you have a DA manual? try setting the needles at the factory recommended settings ... be careful not to tighten them in too much, then back out to the recommended # of turns and try that

Also check ALL of the socket head screws in the crankcase and the ones holding the cylinder down and the carb on and make sure thry are not loose which will leak air

I have a DA50 in a Top Flite P-51 mustang. It didn't get as hot as yours but it did get quite warm. A fellow club member suggested getting more air going to the carb from the firewall so the motor would not be ingesting hot air which could contribute to leaner running. I opened up the airscoop under the wing and cut matching holes in the fuse to allow the fuse interior to become pressurized when flying... then I opened up the hole in the firewall behind the carb to 1.75" dia. This definetly helped. I don't know how to do this in an EXTRA.. but I'm passing the info along anyway

I'll join the club and say it's too lean on the high end. Possibly to the point of the cylinder and ring being toast. You could go back to factory settings but I do not think it will do much good. Maybe even check all the bolts

The weird thing is, I just ran across a brand new one this weekend on a WH Edge that was very close to the same symptoms you are seeing, but no dead sticks and head temps in the 165 - 170 degree range. When cold, it had tons of compression, when warm, it felt as though it had very little, it started like clockwork, but the prop would not windmill and it was turning an MSC 22X8 in the 6800 -6900 range and it was rich as shown by the head temps. I'm wondering if the newer ones have a clearance issue between the ring and cylinder. I have two Da50's in the low 3000 serial number range and neither seem low on compression after warm, even when they were new

Bill,

Reading your post, that particular engine sounds more like a ring that hasn't seated for some reason, or even possibly stuck in the lands extremely early in the life cycle. That same condition could also be true for the engine that satrted this thread, but unfortunately I don't think so.

This is an excellent point for RCIGN, D. Hanson, and Preivers to shed some additional thoughts.

Hard to see all that way to Cape town but 22x8 MenzS is a BIG load on that engine
my off hand guess is overloaded --due to prop load - lean mix- restrictive muffler- low oil% -poor cooling flow
any or all of these
PS it is almost IMPOSSIBLE to over rev the engine - ideally you prop it to run at least 6500 on the ground easily -no matter what the prop used.
running easily of a mix which will easily four cycle , is important to do
Once you have established that full throttle can be made to run rich and lean by shifting high speed needle - you are on your way to being in correct rpm for the prop

My (wild) guess:
1) has been working too hard, too soon
2) on a lean top end mixture
3) causing ring sticking when hot.
4) cooling may be very marginal, if the cowl remnants deflect the air from the cylinder

It may also be a broken ring, but then cold compression is bad.
I take it that all bolts have been checked?

Pat,

The engine in question is on it's 5th gallon on 32:1 ashless. The pilot is a pretty decent, but fairly new gas pilot. He asked me to look into it and help him tune it better. The numbers I quote were after I leaned it. It was 4-stroking allo the way through the transition when I first started. It may have been run a bit lean at first but according the this person it was at the factory settings the whole time which would cause an oil buildup on the ring

I did mention the ring being stuck and we did pull the exhaust off and on that side it looked good. The plug was very close to being fouled due to how rich it was running previously but after 6 pretty hard flights the plug was coming around and the engine was running like one would expect a DA to run. It just felt weird flipping the prop to start it

You say the engine feels weird when you flip it do's it have any compression when you turn it backwards as speaking from previous experience this usually indicates a ring stuck in the land[]