Rotax 912 overhaul

November 24, 2013

The engine of my Ximango is reaching TBO (1200 hrs. for my old 912). Has anybody experience with engine overhaul an can give me advise? I am in contact with Lockwood in Florida and Rotech in Western Canada. Any comments on these two shops? I'll get a propeller overhaul at the same time. What else should I overhaul or replace? Is there a good local source for exhaust parts? Thank you for any advise. Looking forward to your inputs.

November 24, 2013

The engine of my Ximango is reaching TBO (1200 hrs. for my old 912). Has anybody experience with engine overhaul an can give me advise? I am in contact with Lockwood in Florida and Rotech in Western Canada. Any comments on these two shops? I'll get a propeller overhaul at the same time. What else should I overhaul or replace? Is there a good local source for exhaust parts? Thank you for any advise. Looking forward to your inputs.

November 25, 2013

I don't have any first hand experience, but hopefully others will be able to help. Did you scan the knowledgebase? It contains many old forum entries. I put in various search terms and spotted about a dozen related posts which might yield some insights.

Please post your experience and results here as you go through the process so those of us following will be able to benefit. Good luck!

Edited November 25, 2013 by Webmaster

November 25, 2013

I don't have any first hand experience, but hopefully others will be able to help. Did you scan the knowledgebase? It contains many old forum entries. I put in various search terms and spotted about a dozen related posts which might yield some insights.

Please post your experience and results here as you go through the process so those of us following will be able to benefit. Good luck!

Edited November 25, 2013 by Webmaster

November 25, 2013

You think yours is old, my 2005 912UL is approaching 1500 hrs and was just 1 year short of the Rotax extended TBO of 2000 hrs done to all engines from 2006 on. They didn't include mine because of a crank case difference, othewise it also would be eligible for the 2000 hr TBO. I have been told by Dean at Lockwood (and also some other Rotax experienced mechanincs) that my engine should have no problem functioning well to 2000 hrs with proper maintenance and monitoring of the compressions and oil analysis checks. I am a strong believer in Lockwood's service and parts capability. My Lambada is experimental so I do most all of my own maintenance except the reduction gear box thrust washers which I had Lockwood do. It is easy for me to fly the 4 hrs to FL and stay overnite while they service me and then fly home the following day. My opinion is that you are worrying about overhaul way too early like I did until talking with several experienced Rotax mechanics who I met at Dean/Lockwoods two day service school.....Best wishes......Steve Chase in Seneca SC KCEU N24PV

November 25, 2013

You think yours is old, my 2005 912UL is approaching 1500 hrs and was just 1 year short of the Rotax extended TBO of 2000 hrs done to all engines from 2006 on. They didn't include mine because of a crank case difference, othewise it also would be eligible for the 2000 hr TBO. I have been told by Dean at Lockwood (and also some other Rotax experienced mechanincs) that my engine should have no problem functioning well to 2000 hrs with proper maintenance and monitoring of the compressions and oil analysis checks. I am a strong believer in Lockwood's service and parts capability. My Lambada is experimental so I do most all of my own maintenance except the reduction gear box thrust washers which I had Lockwood do. It is easy for me to fly the 4 hrs to FL and stay overnite while they service me and then fly home the following day. My opinion is that you are worrying about overhaul way too early like I did until talking with several experienced Rotax mechanics who I met at Dean/Lockwoods two day service school.....Best wishes......Steve Chase in Seneca SC KCEU N24PV

November 26, 2013

I would echo what Steve said. I went through Lockwood's Rotax maintenance course for the 912/914 a couple of years ago as well. (taught by Dean Vogel). This question came up. As with all aircraft engines you can continue operating beyond TBO "on condition", which is to be determined by your IA. Although my 2003 912s is now beyond Rotax's suggested calendar TBO for my serial number, at roughly 600 hours TTSN it's nowhere near Hobbs time TBO. My compressions are still excellent. It neither leaks nor burns oil and it's one of the smoothest running 912's I've ever flown behind. I've overhauled the carbs, replaced the fuel and coolant lines and kept up with all the SB's and AD's. Given that a typical soaring flight for me is about 20 minutes engine time on the front end and about 15 minutes engine time on the back end, and given the low Hobbs time, I expect to keep my engine going "on condition" for at least a few more years. I would not hesitate to fly it to the west coast right now if the opportunity arose.

Due to the cost of an overhaul for the 912s, my plan is to remove my engine when the time comes and sell it on the Experimental market. Given what I've seen other engines sell for I think it should sell for about $6000-$7000. Then, the plan is to put those funds towards the purchase a factory new Certified 912s to replace it. The swap is fairly straight forward and I'm pretty sure I can do it in less than a day. The cost is comparable to overhaul except I'll have a zero time, factory new engine with all the upgrades that have occurred since my original engine was new.

IRT the Hoffman prop, I recently purchased a zero time prop that had been sitting for about 6 years. It has never been run, still brand new in the box it came in from Hoffman, but Hoffman requires that it be serviced after it sits that long, even if it hasn't been run. There's a Hoffman authorized prop shop in Opa Locka (Miami) Florida that did the service for me. Here's a link: www.avprops.com

They turned it around in less than a week and were a pleasure to work with. My plan is to take my existing prop and have it overhauled, then sell it. I've also had a recent offer to purchase it "as is". Along the way I've learned that older Hoffman 3 position props like mine need to be sent back to the factory in Germany for overhaul because of what is known as the "P mod". This involves replacing the drive pins in the prop blades and can apparently only be done at the Hoffman factory. You can check to see if your prop has the P-mod by looking at the model number. If it has a "P" in it, you're good. Otherwise, it will need to go back to Hoffman in Germany for overhaul. Chances are if your prop is older than mine (i.e., circa 2002), it will need to have the P-mod done. I was told the cost is around $3500 USD, plus shipping.

In any event, I wouldn't be in a burning rush to overhaul unless you're having compression issues.

Hope it helps!

Regards,

John Lawton

Whitwell, TN (TN89)

Ximango #135

November 26, 2013

I would echo what Steve said. I went through Lockwood's Rotax maintenance course for the 912/914 a couple of years ago as well. (taught by Dean Vogel). This question came up. As with all aircraft engines you can continue operating beyond TBO "on condition", which is to be determined by your IA. Although my 2003 912s is now beyond Rotax's suggested calendar TBO for my serial number, at roughly 600 hours TTSN it's nowhere near Hobbs time TBO. My compressions are still excellent. It neither leaks nor burns oil and it's one of the smoothest running 912's I've ever flown behind. I've overhauled the carbs, replaced the fuel and coolant lines and kept up with all the SB's and AD's. Given that a typical soaring flight for me is about 20 minutes engine time on the front end and about 15 minutes engine time on the back end, and given the low Hobbs time, I expect to keep my engine going "on condition" for at least a few more years. I would not hesitate to fly it to the west coast right now if the opportunity arose.

Due to the cost of an overhaul for the 912s, my plan is to remove my engine when the time comes and sell it on the Experimental market. Given what I've seen other engines sell for I think it should sell for about $6000-$7000. Then, the plan is to put those funds towards the purchase a factory new Certified 912s to replace it. The swap is fairly straight forward and I'm pretty sure I can do it in less than a day. The cost is comparable to overhaul except I'll have a zero time, factory new engine with all the upgrades that have occurred since my original engine was new.

IRT the Hoffman prop, I recently purchased a zero time prop that had been sitting for about 6 years. It has never been run, still brand new in the box it came in from Hoffman, but Hoffman requires that it be serviced after it sits that long, even if it hasn't been run. There's a Hoffman authorized prop shop in Opa Locka (Miami) Florida that did the service for me. Here's a link: www.avprops.com

They turned it around in less than a week and were a pleasure to work with. My plan is to take my existing prop and have it overhauled, then sell it. I've also had a recent offer to purchase it "as is". Along the way I've learned that older Hoffman 3 position props like mine need to be sent back to the factory in Germany for overhaul because of what is known as the "P mod". This involves replacing the drive pins in the prop blades and can apparently only be done at the Hoffman factory. You can check to see if your prop has the P-mod by looking at the model number. If it has a "P" in it, you're good. Otherwise, it will need to go back to Hoffman in Germany for overhaul. Chances are if your prop is older than mine (i.e., circa 2002), it will need to have the P-mod done. I was told the cost is around $3500 USD, plus shipping.

In any event, I wouldn't be in a burning rush to overhaul unless you're having compression issues.

Hope it helps!

Regards,

John Lawton

Whitwell, TN (TN89)

Ximango #135

November 26, 2013

Thanks so much for your posts. My engine dates back to 1998 it TBO is 1200 hours or 10 years. My mechanic is not concerned about the calendar time TBO but is very reluctant to let me go past the hobbs limit even though compression looks good. Oil consumption is creeping up slightly. I need to refill about 0.3 liters every 10 hours. I do oil changes every 25 hours. Filter inspections show no metal. At high altitude (>8000 ft) it sometimes runs rough if I let rpm slip below 5000. I guess it runs too rich but nothing shows at the spark plugs. The leading edge of my prop is banged up because of the poor condition of the tarmac at my home airport. Jason from Avprop in Opa Locka just told me they are doing the 'P' modification in house. The prop does not have to go back to Germany. I'll discuss the timing for overhaul with my mechanic again base on your inputs.

November 26, 2013

Thanks so much for your posts. My engine dates back to 1998 it TBO is 1200 hours or 10 years. My mechanic is not concerned about the calendar time TBO but is very reluctant to let me go past the hobbs limit even though compression looks good. Oil consumption is creeping up slightly. I need to refill about 0.3 liters every 10 hours. I do oil changes every 25 hours. Filter inspections show no metal. At high altitude (>8000 ft) it sometimes runs rough if I let rpm slip below 5000. I guess it runs too rich but nothing shows at the spark plugs. The leading edge of my prop is banged up because of the poor condition of the tarmac at my home airport. Jason from Avprop in Opa Locka just told me they are doing the 'P' modification in house. The prop does not have to go back to Germany. I'll discuss the timing for overhaul with my mechanic again base on your inputs.

November 26, 2013

The rough running issue at altitude is likely being caused by the carbs, not the engine. A rich running engine at altitude may or may not show up on the plugs. Don't use that as your only gauge. An EGT is a sure fire way to tell, but I have yet to see a Ximango with an EGT. As you come down in altitude the fuel/air mixture leans and will burn off any carbon deposits that might have accumulated when it was running rich at altitude. When you look at the color of your plugs you are more than likely looking at the mixture condition at idle, since idling is the last thing you do before you shut it down. Also consider that you've likely run a low RPM for a while when taxing in. Have your mechanic do the 200 hour carb inspection. You probably need to replace the carb floats and/or the little valves that hang from the floats that shut off fuel in the float bowl when it is filled. The float valves look like little plumb bobs that hang off the brass float hinge inside the float bowl. Another thing to look for is wallowing or ovaling of the carb's needle and main jets. This is fairly common on the Rotaxes that have some age and is caused by vibration. You can replace both jets for less than $20, so there's really no reason to not replace them when you have it apart. The jets, as well as the float bowl valves and floats, are easily accessed once the float bowls are removed. I'd also consider replacing the diaphragms and the diaphragm springs, too. Any slop or loss of elasticity in the rubber diaphragm and/or their return springs will cause the carb to not altitude compensate properly, resulting in an excessively rich mixture at altitude. The diaphragms are what allow for altitude compensation. The diaphragms are accessed by removing the screws on the top of the carby. All this is very easy to do, but it should be done by someone who is familiar with the Bing beasties. Of course, you need to keep the carbs in balance with each other, too. A typical Lycoming/Continental A&P may not be familiar with the balance procedure or the Bing rebuild procedure. Make sure they are before you turn them loose on it. Better yet, pull the carbs off and ship them to Lockwood for rebuild if you're not comfortable with your A&P rebuilding them. Lockwood will turn them around pretty quickly. FWIW, I've taken my X to 17,500' msl on numerous occasions while flying over "tiger country" out west and it continues to run smooth as silk.

BTW, that is great news on the prop rebuild! That is something new. I swapped emails with both the shop in Miami and Hoffman back in April of this year and both informed me that the P-mod could only be done at the factory. There's something about boxing up a $12,000 prop, shipping it to Europe and hoping you get it back that just bugs me.

Edited November 26, 2013 by Thermalseeker

November 26, 2013

The rough running issue at altitude is likely being caused by the carbs, not the engine. A rich running engine at altitude may or may not show up on the plugs. Don't use that as your only gauge. An EGT is a sure fire way to tell, but I have yet to see a Ximango with an EGT. As you come down in altitude the fuel/air mixture leans and will burn off any carbon deposits that might have accumulated when it was running rich at altitude. When you look at the color of your plugs you are more than likely looking at the mixture condition at idle, since idling is the last thing you do before you shut it down. Also consider that you've likely run a low RPM for a while when taxing in. Have your mechanic do the 200 hour carb inspection. You probably need to replace the carb floats and/or the little valves that hang from the floats that shut off fuel in the float bowl when it is filled. The float valves look like little plumb bobs that hang off the brass float hinge inside the float bowl. Another thing to look for is wallowing or ovaling of the carb's needle and main jets. This is fairly common on the Rotaxes that have some age and is caused by vibration. You can replace both jets for less than $20, so there's really no reason to not replace them when you have it apart. The jets, as well as the float bowl valves and floats, are easily accessed once the float bowls are removed. I'd also consider replacing the diaphragms and the diaphragm springs, too. Any slop or loss of elasticity in the rubber diaphragm and/or their return springs will cause the carb to not altitude compensate properly, resulting in an excessively rich mixture at altitude. The diaphragms are what allow for altitude compensation. The diaphragms are accessed by removing the screws on the top of the carby. All this is very easy to do, but it should be done by someone who is familiar with the Bing beasties. Of course, you need to keep the carbs in balance with each other, too. A typical Lycoming/Continental A&P may not be familiar with the balance procedure or the Bing rebuild procedure. Make sure they are before you turn them loose on it. Better yet, pull the carbs off and ship them to Lockwood for rebuild if you're not comfortable with your A&P rebuilding them. Lockwood will turn them around pretty quickly. FWIW, I've taken my X to 17,500' msl on numerous occasions while flying over "tiger country" out west and it continues to run smooth as silk.

BTW, that is great news on the prop rebuild! That is something new. I swapped emails with both the shop in Miami and Hoffman back in April of this year and both informed me that the P-mod could only be done at the factory. There's something about boxing up a $12,000 prop, shipping it to Europe and hoping you get it back that just bugs me.

Edited November 26, 2013 by Thermalseeker

November 30, 2013

John,

Many thanks for your excellent explanation. Makes a lot of sense.

Well, my carbs have not yet been touched in 15 years. I am sure that is the cause of the high altitude issue. I really need to get them overhauled.

I got quotes from Lockwood and Rotech (located in Vernon, B.C, Western Canada). Lockwood is more expensive ($15800) with a minimum of 8 weeks turnaround time.

The Canadians promise to do it in two weeks. Rotech also was very responsive in their communication, offered three options for the overhaul:

1. Keep the old crankcase and have 1500 hours TBO for $13000

2. For additional $1800 replace the crankcase and get 2000 hours TBO.

3. Buy a new engine and receive a $3500 credit for the old one.

They sent me detailed instruction what I have to ship out and what not, and pictures on howto package the engine. They even offered to send me a crate. They will organize theshipment and the custom transitions and paperwork. Shipping to Canada will be $433including insurance and customs broker.

I am aware that TBO is a manufacturerâ€™s recommendation that IA can waive. However my wife wants me to follow the rules and not try to save money in maintenance. My current plan is to take prop and engine out in the first days of the new year and to get the work done.

What would you recommend? Lockwood or Rotech? Overhaul or replace?

I also might need a new exhaust. Is there a local source for a Ximango exhaust?

Thanks for all your good advise.

Roland Martin

N97SM Ximango S/N 97

New Garden (N57)

Edited November 30, 2013 by Ximango97

November 30, 2013