Replacing Nikasil Cylinders

[sonex1084]

I originally built my AeroVee with the nikasil cylinders but need to replace them due to problems others have previously reported. Unfortunately Sonex is currently out of stock with the Mahle cylinders they currently sell and don't know when they will get a new supply. I found other vendors who sell Mahle 92mm X 82 mm cylinders but I see more than one item number for the same bore and stroke. One vendor sells 98-1993-B and 98-1995-B. The product descriptions are identical. I also see the the same item numbers from different vendors with the notation for thick wall. I really want to use the same cylinder Sonex sells. If anyone has the information from the Sonex supplied cylinder, please pass it on. I would greatly appreciate it. If anyone has any words of wisdom or advice, I would appreciate that also. Thanks, Matt.

[XenosN42]

Good luck removing the Nicasil cylinders from the heads.

[sonex1084]

Good news for me. I got a message back from Kerry. In case anyone else in the future needs the info, Sonex carries the 98-1993-B designation. The 98-1995-B is actually for 94mm pistons (not our size).

[Scott Todd]

I am nearing first start on my Onex. It has Nikasil cylinders. Why don't I want them? Should I replace them before the first start? I searched here and got 6 pages of people saying not to use them but I never really got good reasons why. I reached out to Sonex and am waiting on an reply but I suspect it will be a more politically correct answer than what I'm looking for.

[sonex1084]

Hi Scott, You probably chose the nikasil cylinders for the same reason I did, the lighter weight. Like you I also read the good, bad, and ugly comments about the cylinders. Some folks had a really bad experience with them while others have been using them for several hundred hours and haven't had a problem. I had the cylinders. so I was determined to use them.

I am currently in the phase 1 flight testing phase, so the engine doesn't have a lot of time yet. The first 10 hours were great. Engine temps were coming down and power was excellent. I was really happy. The engine was breaking in nicely. Then I began to notice a problem. My oil/air separator is not plumbed back to the engine. It collects oil like a catch can. After an hour flight I began draining 2 to 4 ounces of oil from the oil separator. At the 10 hour mark I re-torqued the heads and was surprised at how much I had to turn each nut to tighten them to the proper torque. I flew for a few more hours in case the oil loss through the breather was just a break-in issue. Then I did a leak-down test and found air was escaping through the breather tube on two cylinders. I didn't test the other two after the result of the first two.

I decided to remove the heads and cylinders to have a look. I found the cylinders were glazed and scored. I had heard that some nikasil owners found their cylinders had started to mushroom at the heads. They also were surprised by the amount they had to re-torque the heads. Luckily, mine were not mushroomed to where it was difficult to remove the the cylinders from the heads. There wasn't that much time on the engine, so I really don't know if that would have been a problem for me. Now, I don't know if my problems were because of flaws in the nikasil cylinders or because of my flaws in the break-in process. Sonex no longer sells nikasil cylinders so I have no choice but to replace them with steel. The representative I spoke with at Sonex recommended not using nikasil.

This info probably doesn't help you much to determine if you should switch. I read about the possible problems and still wanted to try the nikasil. I just had to try them and hope I was one of the builders who didn't have a problem. But then again, maybe the issue was mine and not the cylinders.

Good luck and have fun on your first flight. I'm looking forward to hearing about it.

Matt

[Scott Todd]

I didn't select the cylinders. I inherited the project from a dear friend that encountered medical problems and had to sell it. This is my third AeroVee. I built one 15 years ago that I still fly in a small biplane. I briefly owned another one on a used Sonex. I sold it after a few hours.

I don't know all the issues but if it may be a problem with disassembly down the road, I would rather replace them now before its even ran. I don't mind the weight, especially in the nose.

[rtro461]

I have the same issue. I have the Nikasil cylinders in a still yet to be assembled Aerovee 2.1 I picked up for my Sonex build. The engine build is not started so I am just watching what is said about Nikasils.
Is this a flight safety problem or a maintenance problem? Has any Nikasil equipped engine stopped while running in flight or on the ground? Or is the issue that the head becomes difficult or impossible to remove after a number of hours? Is this a problem with all Nikasils or just a few?

[XenosN42]

I have the same issue. I have the Nikasil cylinders in a still yet to be assembled Aerovee 2.1 I picked up for my Sonex build. The engine build is not started so I am just watching what is said about Nikasils.
Is this a flight safety problem or a maintenance problem? Has any Nikasil equipped engine stopped while running in flight or on the ground? Or is the issue that the head becomes difficult or impossible to remove after a number of hours? Is this a problem with all Nikasils or just a few?

I had the Nikasil cylinders installed in the AeroVee in my Xenos. I had the same issues the previous posters described. First, when you retorque the heads you will notice that you'll need to tighten the nuts an excessive amount. That is because the cylinders are deforming where they are in contact with the heads. It will be difficult to keep your valves properly adjusted.

After some number of hours, 40? 50? 60? who knows, the cylinders will have deformed enough that they will be difficult or impossible to remove from the heads.

Does it affect all the Nikasil cylinders? I honestly don't know for sure, but I'd bet the answer is yes. I know there are builders that have used the Nikasil cylinders for hundreds of hours. Ask them: have they ever removed the heads? Also ask yourself: why doesn't Sonex sell them any longer?

It's not a flight safety issue IMO. They cylinders won't explode, it'll just be next to impossible to keep the valves properly adjusted.

You'll have enough to keep yourself busy during the 40 hour flight test period. I'd recommend that you save yourself aggravation by spending a few bucks now and buying replacement cylinders.

[WesRagle]

HI Guys,

I know nothing about this but ... I ran across this over on "homebuiltairplanes".

https://www.homebuiltairplanes.com/forums/threads/nikasil-cylinders.34635/page-4#post-602638

Posts near the bottom of the page are interesting.

Wes

[mike.smith]

My Kitlog site has information about what many (most?) of us were seeing with the Nickasil cylinders. The fact that Sonex doesn't make them available anymore should tell you something. My advice = don't use them, and/or replace them. If you do fly with them, DO OIL ANALYSIS EVER OIL CHANGE!!

http://www.mykitlog.com/users/display_l ... 380&row=57