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Need Engine repair advice

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Doing my 9th annual inspection and looks like I have a burnt exhaust valve on Cylinder 6.
Lycoming YIO-540-D4A5 purchased through VANS. Has about 900 hr on it.

Last condition inspection #6 compression was 76/80, (all cylinders were 76-78)

Current compression all except #6 still in 76-78 range. #6 was 25.

Took this picture with a boriscope.Image_2023-02-26 16_01_34_708.JPG

Never really done any engine work before, and getting a local A&P involved to help me, but from my research so far it appears that it is a quite burnt exhaust valve. Articles I have read say if valve is GREEN is NO-GO and the cylinder needs removed and valve replaced, not just lapped in place.

Just want to confirm that before pulling the cylinder.

Also does anyone have a good source for replacement cylinders. pilotshop, aircraft spruce, etc don't seem have them in stock.

Or would you normally pull the cylinder and then send it to an overhaul shop and wait for it to be returned? Or other options?

Normally would you just replace the cylinder, or also the piston assembly.
 
I would just replace the valve.
Inspect other parts (valve seat, valve guide, piston/rings, etc) and replace only if their condition warrants it. My two cents.
 
Hey Bill,

I would check with the local maintenance shops in the Atlanta area. One of them might have the proper tooling to replace that valve. You’ll still need to remove it but it will be cheaper and faster than sending it off or waiting for a new one. You should hone the cylinder, replace the rings and get new gaskets while it’s apart.

Are you still an active skydiver? D13620 here, haven’t jumped in about 15 years.
 
New cylinders are pretty much unobtainable right now, so that kind of closes off one of the legs of your decision tree….I’d find a local cylinder shop with a good reputation and send it off for a valve and anything else they think is needed.

A long time ago, everyone repaired cylinders. Then production of cylinders by three manufacturers flooded the market with new jugs at such good prices that no one serviced them - they just bought a new assembly (including piston) and installed them. Now with essentially no supply of new replacements, I bet we’ll see a lot more repair again. Cycles…..
 
Hey Bill,

I would check with the local maintenance shops in the Atlanta area. One of them might have the proper tooling to replace that valve. You’ll still need to remove it but it will be cheaper and faster than sending it off or waiting for a new one. You should hone the cylinder, replace the rings and get new gaskets while it’s apart.

Are you still an active skydiver? D13620 here, haven’t jumped in about 15 years.

Thanks, and yes still active skydiving. D-16716, 30 years and counting
 
+1 for Twin aircraft engines, they helped me with a jug that needed some love and seemed very strait shooters.
 
Hi Bill, just curious, did this just happen between condition inspections, or is the borescope a new tool in your arsenal?
 
Hi Bill, just curious, did this just happen between condition inspections, or is the borescope a new tool in your arsenal?

Boriscope is new tool. Compression was fine last condition inspection, but not sure what it looked like. Put about 150 hr on it since last year.
 
any cyl repair shop can do that. Just needs a new valve and re-grinding. There are several shops that will sent you a fresh rebuilt cyl for $800-1000 and you send back yours after the swap. Makes the replacement much easier. Just remember that the fresh cyl will be honed and the break in protocol must be followed. If you find a local shop, you could bring them the cyl and they could just do the valve replacement without honing. This would be a lower cost, but may need to find a cylinder shop as they are typically the only ones that grind valves and seats. I suspect there are a few exceptions to that though.

All but certain that the seat will need grinding and depending upon it's condition, may need to be replaced.
 
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Definitely a valve in distress that needs to be addressed. Not sure that it's not repairable though. I can't tell from the photo, but it is possible the seat is still not excessively burned.

There is a procedure to re-hone the valve guide and seat in place without pulling the cylinder, and what I would attempt before pulling the cylinder. The reason the valve is burned is normally because it's not rotating - so that should be addressed.

If the valve seat is severely burned, then pulling the cylinder and getting it OH'd is likely the fastest return to service.
 
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Thanks everyone. Took the cylinder down to twin aircraft engines today. Decided with plane down anyway that was good time to get prop overhauled as well so got that taken to the prop shop as well. 9 years and 900 hr, guess this is the time to get her back into top shape.
 
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