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What engine?

lycon built my o 200 and so far i like it better than expected really smooth
shawn

How close is it to TBO? If two are bad, how are the other four? I haven't seen people have much luck replacing one or two cylinders, unless there was something wrong that hurt them like a vacuumn leak or similar problem. Usually if two are worn out, the other four are right behind.

A mechanic I worked with years ago thought One Stop Cylinder Shop in california did a pretty good job.

John,

I have had numerous conversations regarding Continental cylinders and the age of same with some pretty knowledgeable folks.

Their theory to explain why we were changing so many cylinders on IO 520 engines was that we were re-using cylinders. The point is, it becomes virtually impossible to track just how old a cylinder is after a few re-ups.

So, my recommendation is this: If you KNOW those cylinders are pretty new (as in they came with a new engine and you can track their history) you might have them overhauled.

That said, recently, in at least some cases, NEW cylinders have been only slightly more expensive than an overhauled one. Don't know if that's true for the engine you describe, though.

In any case, if your cylinders are old, or of unknown age, you might consider new cylinders instead of overhauled, and sell what you have, or exchange.

MTV

Cylinders quite often will hold good compression up until the point the rings wear thin enough and lose tension, then your compressions are gone. So, you could replace two and have two more go bad in 100 hours or less.
On another note, Continentals are notorious for having inconsistent compression checks. In other words one will test real low, but if flown around the pattern and re-tested, it will be fine. Have these cylinders been running low comps? Have you had another test run?
If in fact two are bad, I'd replace all six. It's unlikely in my opinion that if all six are of the same age that two are worn out and the other four aren't.
Tried telling my Father that years ago after he lost a cylinder on his Mooney. He had it replaced, and lost the second one while hard IFR. I guess it's not fun IFR in a three cylinder Mooney

Hi jmtgt,
no idea what the right answer is... but, FWIW... I do have a fair amount of time in a Lycon O-360 cub and a Lycon (topped) O-520 Bird Dog. Both get worked hard and both put a smile on my face everytime I get in them.... that's the route I will go when mine is ready for an o/h.
Take care, Rob

John, is it leaking thru the exhaust? The weak link on at least the smaller Continental engines (O-300 & below) seems to be the valve guides, esp on the exh side. They wear, let the valve rock around, and pretty soon it doesn't seat worth a darn & your compression readings go to hell. Doesn't seem to affect the way they run though, in my experience, at least until they're really down there (like 40/80).
I think the geometry of the rocker-arm to the valve stem is not quite right, and the rocker-arm puts a side load on the valve stem leading to this valve guide wear. On the other hand, the weak link on the Lycomings seems to be the cam & followers rusting & coming apart. Ain't nothing perfect.
Yours might just need new guides, but then as long as they're off you might as well go for new rings, hone, etc. There's an AD on the 200/300 series cylinders about rocker-arm shaft boss thickness, a lot of older factory cylinders's get red-tagged on that one. Don't know if it's applicable to the IO-360.

Eric

Lycon, great folks, real quality, first rate customer service.
The historical difficulty with the valve train on these things (older Continentals) are the main culprit. Typlically, the cylinders/pistons/rings are good but the older jugs had a problem with guides and seats because of it. According to "Those In The Know", this fault has been corrected for a few years. If that's the problem with yours, you could have them OH'd with after market parts, or buy new which will be about the same price and new is, well, new.
There's a lot of factors here too, hot or cold check, blowby in crankcase or exhaust and then there's the service buliten from TCM with revised parameters for the xx/80.
Of course, the biggest problem is that you only fly 5-6 hours a year........

Hi John,
Check prices for a rebuild or exchange from One Stop in Oceanside, Ca and Tim's Aircraft Engines in Long Beach, Ca. Both have rebuilt cylinders in stock and can quickly ship to you.