914 leak down

[rhtrudder]

• Over 1900 hrs on my engine, no 2 always felt a bit soft in compression when flipping over the prop, leak down showed 70/80 , rest about 75/80 , going past the rings , should this be a concern or just keep flying, engine doesn’t use any more oil than usual 

[facthunter]

How many hours do you intend to run it to?  Nev

[rhtrudder]

Only private flying, having trouble trying to justify over $50K on a replacement so I guess I keep up the service and hope for the best, worked okay so far , Wally tells me plenty have well over 3000 up

[facthunter]

It will contaminate your oil a bit more than when it was younger. Parts are too expensive to start fiddling. Unlike cars they run at about 75% power.  When you pull the engine through if you know how a good cylinder feels, you can relate to that.  It's not a bottle of wine that improves with age. Depends a lot on where you operate from. Nev

Edited May 26, 2024 by facthunter

[skippydiesel]

  On 26/05/2024 at 7:05 AM, rhtrudder said:

Only private flying, having trouble trying to justify over $50K on a replacement so I guess I keep up the service and hope for the best, worked okay so far , Wally tells me plenty have well over 3000 up

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Go with Wal's advice.

 

You may as well keep using while operating perimeters are all in the green.

 

If not already, keep a log of oil added against hours flown - when oil added starts to approach Ly/Con normal consumption, might be time to consider your options.

 

May be instructive to do the leak down cold & hot.  Do cold, then go fly, to get engine well heat soaked and do the test again.

[Blueadventures]

  On 26/05/2024 at 7:05 AM, rhtrudder said:

Only private flying, having trouble trying to justify over $50K on a replacement so I guess I keep up the service and hope for the best, worked okay so far , Wally tells me plenty have well over 3000 up

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Maybe have a look with a borescope to see bore and valve condition; will give peace of mind.

Edited May 26, 2024 by Blueadventures

[facthunter]

What in Dog's name has the normal oil consumption of a Lycoming got to do with this motor?  Nev

[Thruster88]

  On 26/05/2024 at 8:10 AM, facthunter said:

What in Dog's name has the normal oil consumption of a Lycoming got to do with this motor?  Nev

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We all know Skippy will never miss an opportunity for a dig.

[Arron25]

Fly Tornado?

[facthunter]

Lycomings are not known as oil burners in any case.  FACTS are important. Nev

[facthunter]

Quite a few Lycoming cylinders are NITRIDED.  Nev

[rhtrudder]

  On 26/05/2024 at 7:40 AM, skippydiesel said:

Go with Wal's advice.

 

You may as well keep using while operating perimeters are all in the green.

 

If not already, keep a log of oil added against hours flown - when oil added starts to approach Ly/Con normal consumption, might be time to consider your options.

 

May be instructive to do the leak down cold & hot.  Do cold, then go fly, to get engine well heat soaked and do the test again.

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Would it be possible to replace the pistons and rings and maybe valve guides give the old cylinders a hone and go again, I reckon the bottom end looks solid, could be a cheap way out although I have out jewed myself in the past with mixed results 

[skippydiesel]

  On 27/05/2024 at 7:40 AM, rhtrudder said:

Would it be possible to replace the pistons and rings and maybe valve guides give the old cylinders a hone and go again, I reckon the bottom end looks solid, could be a cheap way out although I have out jewed myself in the past with mixed results 

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Ask Wal.

 

I don't think you can hone or rebore the Rotax 9 cylinders. 

 

It may be possible to fit an aftermarket kit even a big bore upgrade: 

 

https://stolcreek.com/bigborekits

https://www.edgeperformance.no/big-bore-faq

https://zipperbigbore.com/zipper-1417-turbo/

 

[Blueadventures]

  On 27/05/2024 at 7:40 AM, rhtrudder said:

Would it be possible to replace the pistons and rings and maybe valve guides give the old cylinders a hone and go again, I reckon the bottom end looks solid, could be a cheap way out although I have out jewed myself in the past with mixed results 

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I'd phone Wal again and ask a quote to look at your engine and assess it ( compression check, differential pressure check cold and hot) also a quote to replace rings etc.  

[skippydiesel]

An echo!

[F10]

Not sure why Lycomings are coming up in a Rotax 914 chat? My Rotax 912 ULP is running on condition. These are things I have found out/experienced with leak-downs. Firstly, it is a pretty good check, but it is not as bullet proof as some think. If you have any doubts, a borescope look tells you a lot! It will show valve condition, signs of valve heat stress, will show. and valve seating health, very often the cause of low compression. A borescope will also show health of cylinder walls. It is a pretty reliable check and will tell you of pending problems, whereas a leak-down is a snapshot health check. I have head a good borescope, one that can look in all directions are around $300. A good investment? I think so. 

 

Having said that, one thing I found was getting the engine up to a reasonable temperature is important. I recently replaced my Bolley prop, during my last annual. The old one had been on the aircraft for 10 odd years and was showing signs of corrosion. In for a penny, in for a pound, replacing the hub and blades, cost only slightly more than keeping the old blades. After running the engine for a while, to check static RPM and vibration levels, we carried out a compression check. The engine returned figures of 77/80, 78/80, which a new engine would. Doing a leak-down with a hot engine makes a difference, although taking out hot spark plugs is good juggling practice!

 

As I recall my leak-down minimum is 65/70. Certainly anything under 65 is a worry, but it could be just a badly seating valve. A borescope will tell you that before you do anything expensive. There are crafty tricks out there, to also grind and re-seat valves, without removing the cylinder head! 

[rhtrudder]

  On 28/05/2024 at 12:30 AM, F10 said:

Not sure why Lycomings are coming up in a Rotax 914 chat? My Rotax 912 ULP is running on condition. These are things I have found out/experienced with leak-downs. Firstly, it is a pretty good check, but it is not as bullet proof as some think. If you have any doubts, a borescope look tells you a lot! It will show valve condition, signs of valve heat stress, will show. and valve seating health, very often the cause of low compression. A borescope will also show health of cylinder walls. It is a pretty reliable check and will tell you of pending problems, whereas a leak-down is a snapshot health check. I have head a good borescope, one that can look in all directions are around $300. A good investment? I think so. 

 

Having said that, one thing I found was getting the engine up to a reasonable temperature is important. I recently replaced my Bolley prop, during my last annual. The old one had been on the aircraft for 10 odd years and was showing signs of corrosion. In for a penny, in for a pound, replacing the hub and blades, cost only slightly more than keeping the old blades. After running the engine for a while, to check static RPM and vibration levels, we carried out a compression check. The engine returned figures of 77/80, 78/80, which a new engine would. Doing a leak-down with a hot engine makes a difference, although taking out hot spark plugs is good juggling practice!

 

As I recall my leak-down minimum is 65/70. Certainly anything under 65 is a worry, but it could be just a badly seating valve. A borescope will tell you that before you do anything expensive. There are crafty tricks out there, to also grind and re-seat valves, without removing the cylinder head! 

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Worst cylinder was no 2, left front, could definitely hear bubbling in the oil tank, so I reckon the valves are good, 70/80 , the bore scope sounds a good idea but I’m not sure I’d know what I would be looking at, wonder if just a set of rings would make a difference, read that the bores hardly wear, hard as a cats head, found on eBay a full set of pistons and cylinders only 95hrs, $1200 plus freight from the US

could be a scam but might be worth the gamble.

[rhtrudder]

  On 28/05/2024 at 12:30 AM, F10 said:

Not sure why Lycomings are coming up in a Rotax 914 chat? My Rotax 912 ULP is running on condition. These are things I have found out/experienced with leak-downs. Firstly, it is a pretty good check, but it is not as bullet proof as some think. If you have any doubts, a borescope look tells you a lot! It will show valve condition, signs of valve heat stress, will show. and valve seating health, very often the cause of low compression. A borescope will also show health of cylinder walls. It is a pretty reliable check and will tell you of pending problems, whereas a leak-down is a snapshot health check. I have head a good borescope, one that can look in all directions are around $300. A good investment? I think so. 

 

Having said that, one thing I found was getting the engine up to a reasonable temperature is important. I recently replaced my Bolley prop, during my last annual. The old one had been on the aircraft for 10 odd years and was showing signs of corrosion. In for a penny, in for a pound, replacing the hub and blades, cost only slightly more than keeping the old blades. After running the engine for a while, to check static RPM and vibration levels, we carried out a compression check. The engine returned figures of 77/80, 78/80, which a new engine would. Doing a leak-down with a hot engine makes a difference, although taking out hot spark plugs is good juggling practice!

 

As I recall my leak-down minimum is 65/70. Certainly anything under 65 is a worry, but it could be just a badly seating valve. A borescope will tell you that before you do anything expensive. There are crafty tricks out there, to also grind and re-seat valves, without removing the cylinder head! 

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How many hrs on your engine 

[F10]

Lots! 2500. But still returning great leak-down numbers and regular oil changes/oil filter checks, show no glitter! The Rotax 80 Hp 912 ULP engines are the jewel in the Rotax crown, if you as me. They are pretty unstressed and I have heard when opened up after 5000 Hrs, you can still see the honing on the bores. As I said, I have heard this. Anyone with more info, happy to hear it.

[BrendAn]

  On 27/05/2024 at 12:17 AM, facthunter said:

Quite a few Lycoming cylinders are NITRIDED.  Nev

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My Lycoming clock doesn't burn a drop of oil. It is timed out or on depending how you look at it 😁

[BrendAn]

  On 28/05/2024 at 1:52 AM, BrendAn said:

My Lycoming clock doesn't burn a drop of oil. It is timed out or on depending how you look at it 😁

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[rhtrudder]

True, the 914 is a 80hp with a turbo, low compression on start up , HP comes up when over 30 on the map gauge 

[BrendAn]

  On 27/05/2024 at 7:40 AM, rhtrudder said:

Would it be possible to replace the pistons and rings and maybe valve guides give the old cylinders a hone and go again, I reckon the bottom end looks solid, could be a cheap way out although I have out jewed myself in the past with mixed results 

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the bloke in moorabbin that hots up rotax motors charges around 10 k for a big bore kit fitted but it may be more now like a lot things post covid.

[facthunter]

Most aero engines don't have the reserve of strength and heat dissipation to cope with  power increases safely.  Nev

[BrendAn]

  On 28/05/2024 at 5:34 AM, facthunter said:

Most aero engines don't have the reserve of strength and heat dissipation to cope with  power increases safely.  Nev

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I know someone that had his 912 bumped to I think 115 HP with the big bore kit done at Moorabbin and it has proven reliable.