I noticed there are couple of lines running through the cylinder wall of my DL50, see the picture. What could cause them? Scratches left by a bad ring?

The compression on the engine is OK, but not great. When comparing with another DL50 at our flying field, that engine's compression when turning the prop CW is the same as mine when turning the prop CCW. Since compression at CW should be much ore stronger than at CCW, my DL50 is compression is weak than the other one.

Any comment?

They look like they're from manufacturing or assembly. I'd say you have it documented here now, run it, if it runs good don't worry about it, if it doesn't and you bought it in the USA send it back. If you bought it from China you'll learned why it's better to buy from a dealer in the USA.

Looks like they might have been made by a machine tool as it was removed or inserted in the cylinder, or something dragging behind the tool. A small knife blade could do similar if someone was trying to pick something out of a cyinder for some reason.

Not bad though and likely won't have any effect on the engine's performance. Just use a good oil and mix ratio and forget it.

Hi,

If you ran a little higher oil ratio, the ring seal would be better and you would not see any loss of performance. Try 40:1 rather than say 50:1.


Elson

When cylinder was honed, the marks could be from parts of the hone that may have broke up from hitting a sharp edge. Hard to tell for sure in the photo. Capt,n

Thanks a lot for the feedback.

Since most of these lines are across the wall instead of vertical, I tend to agree their impact to the performance is small.

I originally thought there is a sharp point on the ring and when the piston is made moving up and down (slowly), the sharp point scratched the surface.

BTW, I have checked my DA50 and found no such lines across the cylinder wall.

No worries, just go fly it and enjoy.