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 by facthunter

[skippydiesel]

29 minutes ago, 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

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]

50 minutes ago, 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

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

Edited May 26 by Blueadventures

[facthunter]

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

[Thruster88]

12 hours ago, facthunter said:

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

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]

23 hours ago, 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.

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]

17 minutes ago, 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 

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]

28 minutes ago, 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 

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]

6 minutes ago, 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! 

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]

25 minutes ago, 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! 

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 10:17 AM, facthunter said:

Quite a few Lycoming cylinders are NITRIDED.  Nev

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

[BrendAn]

Just now, BrendAn said:

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

 

[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]

18 hours ago, 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 

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]

2 minutes ago, facthunter said:

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

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.