Interesting topic but isn’t it time we moved on from these engines?
Our Cessna 150 fly about 450 hours a year. Actually as close to 449 as I can get before the annual. In the last year we have had two sticking valves on our o200s. We have no home maintenance and because of the nature of the work they do (flight instruction) we are not allowed to work on them. Fortunately they didn’t go tech away from base but its still a 120 quid call out fee to maintenance plus a 500 quid bill for a repair.
Also in the last year we have had 2 spark plus failures and a mag failure.
In this day and age should we really be having such problems?
Interesting topic but isn’t it time we moved on from these engines?
I wish, just the economics don’t work in favor of it. Not yet.
However, even though these engines are ancient low tech rubbish, they are so primitive that medium skilled people in the field all around the world can repair pretty much anything about them. Nothing about them is “high precision”. And the reliability is still not too bad but considerably worse than their reputation. One example is the Centurion which has a kind of a poor reputation for reliability compared Lycosaurus but if you look at the numbers, it’s reliability has been significantly higher for a many years now.
This on AVWeb refers to using dental floss tied to the valve stem to retrieve it….
That better not work! The clearance between the valve and valve guide should be so small that there is no space for dental floss. If that method works, you need a new valve and valve guide. Also it doesn’t really add anything on top of the magnet technique because you would still have to align the valve with a holder through the lower spark plug hole.
You have the two spark plug holes to work through, but much more useful is the exhaust port, when the exhaust is removed.
Removing the exhaust can be a hell of a job, especially on a turbocharged aircraft. I deliberately did not go down that route but two spark plug holes is enough to get this job done without too much difficulty. I promise you, the first time you get that valve back in, it’s a feeling of success almost second to none 
Nothing about them is “high precision”
Then can you explain to me why its 16500 pounds to get one overhauled?
Then can you explain to me why its 16500 pounds to get one overhauled?
It’s mostly cost for parts, about 2/3. The rest is a lot of hours to disassemble, inspect, assemble, test, paperwork. There are also considerable expenses for warranty, that needs to be in the price.
The cost for parts and machine work to overhaul an O-200 is roughly between $3K and $10K depending on how you do it. That assumes no major bottom end components need replacement.
I have seen a Lycoming AEIO-540 angle valve engine overhauled to new limits for $15K in parts and machine work.
The reason I’ll remain using air cooled, opposed, non-geared, non-turbo carbureted aircraft engines is because my existing engines will be kept airworthy for as long as I want to fly them for limited out of pocket cost. Nothing is perfect but they are definitely a major attraction to aircraft ownership for me.
Doesn’t an overhaul require
An IO540 is about $30k at a top shop in the USA.
An overhaul can be done with or without new cylinders, depending on the condition of the existing cylinders and the cost to overhaul existing cylinders within the specific circumstances and resources of the owner. NDT can be cheap, depending on the specific circumstances and resources of the owner. Parts cost money, the amount depending on where you buy them. 
It cost $15K for parts and specialized work to overhaul the AEIO-540 I mentioned. As an aside, that engine and the aircraft it was installed in was bought for $80K from an insurance company and sold for IIRC $170K, albeit with about $25K spent and at least a year of screwing around with the local FSDO. I wasn’t financially involved but it was interesting to see. For the owners it was just a way to make a little money and have some fun using their skills and the hangar they have anyway.
If I had the feeling that owning an aircraft required me to submit myself to a totally preordained and regulated business process, I’d sell mine. That’s actually one reason I like owning aircraft now, and have limited my involvement with new cars and motorcycles. Contrary to popular perception, at least for N-registered planes and particularly in the US, there is more scope for flexibility and creativity when dealing with aircraft, and a whole network of resources.
From @pilot_dar ’s post it sounds like removing the exhaust is key to getting the valves back in. So the “rope trick” is really there to avoid removing the exhaust. The Lyco exhaust stud nuts are very expensive and arguably should not be re-used.
I wonder if there is a tool which can pick up a valve stem through the spark plug hole, and push it back up into the freshly reamed guide?
Peter wrote:
The Lyco exhaust stud nuts are very expensive and arguably should not be re-used.
They are 20p each from LAS! Even the studs themselves are under a fiver. (Or does every nut require an EASA form 1 if you’re EASA regulated?)
