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Yes we have had 2 engines replaced. It was a waste, they are in excellent condition. I've been using parts from one.

We are now on an oil analysis program and are scoping cylinders instead of doing tbo. But if they have problems or start to show signs of high wear, we will swap out the engine.

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Hi Corey,

So long as the engine passes the on condition inspection which is nothing more than an annual there is no reason to dump an engine. I have friends with 3k-4k hrs. on their engines.  No use scoping cylinders either. Cylinders are nikasil and are so hard it takes a diamond hone to even touch them. If you're using 100LL then it may be good to have the piston tops cleaned and maybe the heads worked on to get rid of the lead around the valves and guides and then the gearbox.

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The areas of concern are valves cupping or valve seats wearing, which is a good idea to scope the cylinders to see if they start doing that, and keep up with the gearbox maintenance too. It's just a quick job to do while you pull the plugs.

As with any recip, those valve stems are the real weak point to just running on condition forever. Pretty much everything else that I can think of off the top of my head can be detected as a failure in progress. Eventually those stems are gonna let go. What I don't know about rotax is if they give suddenly, or stretch and become noticeable first.

On lycomings, there were a few valves that had that problem. They would break suddenly.

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Corey, are you aware of any valve problems on a Rotax that were not related to having air in the lifters, or using leaded fuel?

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Ho Corey,

You should never see valve cupping in a Rotax. The valves are super hard. Armor coated. They are not even one piece at MFG, but two pieces welded together. You can not do a valve job on them because they are so hard. So all they would ever need is some cleaning especially after using lots of 100LL. The guides may need reaming due to lead and the seats recut. 

If a stem on a valve were to break you would know it instantly. That has happened on a couple worldwide, but is very rare.

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What I am saying is, I would prefer them to slowly give way. That can be detected before failure. Sudden failures are very bad. I don't like sudden failure modes.

Scoping a cylinder also gives a bit of info on cylinder health. Just like looking at the end of a spark plug. I had one that was starting to use a bit of oil. Scoping cylinder 4 told me everything right then, oil ring needed replaced.

It only takes me a minute to look inside. Could probably even just do this every couple hundred hours and not miss a thing.

It is quite unlikely to find anything, I agree, but that can be said about pretty much every inspection.

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