Compression failure Nikasil Cylinders

[bakfly]

Hi all,
After just 3hrs flying and trying to tune #2 .5 needle, the Aerovee Engine with Nikasil Cylinders developed a problem. We checked the ignition, retightening the cylinder heads and readjusted the valve clearance. Then we discover the problem was that three out of four cylinders did not have any compression. After taking the Cylinder heads and cylinders off on right hand side of the engine, we discovered apart from the cylinders are glazed already, one of the Pistons has partly lost its black coating. It looks like it has just flaked off. In addition to that it looks like that the Piston Rings has not been in contact with the Cylinder wall on some places, meaning that the cylinder is not perfectly round. I have not taken the cylinders off on the other side yet but I expect they will be the same. During ground engine test and test flying the Cylinder head and exhaust gas temperature never went above the maximum allowable temperature.
Does anybody had the same sort of problems with the Nikasil Cylinders and Pistons?

Regards,
Peter Bakker,
Sonex #1430, Aerovee 2.1

[mike.smith]

Before I first flew I had very low compression in one cylinder. Air was leaking from the exhaust valve. I rechecked the valve gaps and ran the engine a few times on the ground. When I rechecked, that same cylinder was nearly 80/80. I have about 52 hours on mine, and no issues.

[MichaelFarley56]

I'm sorry to hear this Peter. I'm at a loss as to what the issue may be.

I have around 130 hours on my Nikasil cylinders and have not had an issue with them. During my last Condition inspection in April, I checked the compression with the engine cold and all compressions were great.

[GWMotley]

If anyone remembers, I posted last year that I had to replace all my cylinders, some for a second time. I found that the cylinder head rim had become distorted and rolled over to form an edge which made it very very difficult to remove the heads. I have since switched to steel cylinders. While they are heavier than the niks, they added weight actually Improved the handling of the aircraft as I believe I was too neutral in CG. Check them carefully next time the heads are off guys.

[bakfly]

Yesterday, I took the left-hand side cylinder off. The Pistons and rings are looking ok but the cylinders walls are bad. The wall surface looks like it is bobbling/lifting off. It is sort of a rim running for the bottom to the top of the cylinders at the bottom side of the engine. I have to replace all the Cylinders and Pistons but I would never use the Nikasil Cylinders anymore.

[tonyr]

Hi Peter,

Sorry to hear your engine is having issues with the cylinders, a bit of a bummer at this early stage.
Sounds like a manufacturing defect.
Hopefully you can get it sorted soon and replaced with the standard stuff?

Cheers
Tony

[bakfly]

Good news, :D Sonex has shipped out a complete set steel cylinders replacement free of charge arriving at the middle of this week. Hopefully we can continue test flying next week. I would like to thank Sonex for a resolving this issue very quickly and satisfactory.
Cheers,
Peter

[Brett]

☺

[fastj22]

That is outstanding customer service. I've had two SBs on my plane that Sonex quickly shipped me replacement parts on their dime.
My only nit with them is the shipping cost of a replacement wheel pant. :o I kid. Ok, only slightly.