912ULS maintenance

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Wagondriver

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I am looking at and probably going to buy a plane with two 912ULS engines on it. They have right at 1000hrs. What service items are coming up at 1000hrs? I can, and do, look these things up on the internet, but I am interested in hearing from people familiar with these engines.
Mechanical fuel pumps and fuel lines have been replaced at about 980 hours. They have been run mostly on unleaded fuel, but have seen some 100ll, but it sounds like only on long cross country trips.

What areas should I pay special attention to when I inspect it prior to purchase?
 
Wagondriver said:
I am looking at and probably going to buy a plane with two 912ULS engines on it. They have right at 1000hrs. What service items are coming up at 1000hrs? I can, and do, look these things up on the internet, but I am interested in hearing from people familiar with these engines.
Mechanical fuel pumps and fuel lines have been replaced at about 980 hours. They have been run mostly on unleaded fuel, but have seen some 100ll, but it sounds like only on long cross country trips.

What areas should I pay special attention to when I inspect it prior to purchase?
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Gearbox inspection on each and probably also due for carb clean and re-balance. Also look into if it was all the rubber hoses or just the fuel lines replaced. On your compressions - you’ll want them run at 87 instead of 80.
 
The serial numbers. Some early 912ULS' have a TBO of 1,200 and 1,500 hrs respectively. No worries on 100LL as long as it's run < 30% of the time otherwise more frequent oil changes should have been performed. As noted above gearbox inspection at 1,000 hrs so that will take care of any lead in it. Verify rubber replacement (coolant hoses, oil and fuel lines if not teflon, carb sockets, carbs, expansion back plate) was performed within the last 5 years.
 
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In addition to the above note about some earlier models having a 1200 hour TBO, there was an issue with the earlier models as well with case fretting which typically would cause the start of oil leaks around a thousand hours and there's really not any fix other than overhaul/replace. I think they fixed this problem in 2006 or 2007, but you would need to check with the case number to find out if it is a new or old design.
 
As noted, some of the early engines initially had a low TBO, but those have been "extended".
There are about a bazillion service bulletins issued by Rotax for this and that. You can look them up by serial number.
Useful resources - https://www.flyrotax.com/p/service/technical-documentation https://www.rotax-owner.com/en/
The engines are due for the gearbox inspection at 1000 hours.
If you see any signs of leaks, you have a problem. Look carefully. Any leak. There have been some case cracks on early engines.
The 912 ULS may or may not have the "slipper" clutch that protects the engine in the event of a prop strike.
Carb floats have been recalled many times. I have switched to the Marvel Schebler floats at 200 ****ing dollars for 4 stupid plastic pieces...
 
Engine serial numbers are 4425731 and 732, appears they are from last half of 1999. Which from my scratching the surface of 912 info means 1200 or 1500 tbo?, and not available for extension to 2000 hrs.

Carb floats were checked and weighed in one log book entry. Logs show friction torque checks at 38# in a recent entry.

What does a gearbox inspection cost? time to complete? How much cost for parts is involved in replacing all the rubber parts?

Thanks
 
Wagondriver said:
What does a gearbox inspection cost? time to complete? How much cost for parts is involved in replacing all the rubber parts?
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Hi.
The Gearbox is around $2600.00 to rebuild, if no complications. The time to test / rebuild is 5-600.00Hrs.
You can add to those the BRS, all the SBs, alerts,... some new ones just came up, you can end up with $11-12,000.00, if you have to do all, hoses, BRS,... annual.
The worst thing is that most mechanics are not qualified (know enough about it) to do the job, look first. Get informed in your area.

PS- There is a New owner, see: https://www.pilotsofamerica.com/community/threads/seek-input-on-buying-a-lsa.148631/, he went quiet after purchase, but you may want to see if it helps to get some info.
 
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Wagondriver said:
Engine serial numbers are 4425731 and 732, appears they are from last half of 1999. Which from my scratching the surface of 912 info means 1200 or 1500 tbo?, and not available for extension to 2000 hrs.

Carb floats were checked and weighed in one log book entry. Logs show friction torque checks at 38# in a recent entry.

What does a gearbox inspection cost? time to complete? How much cost for parts is involved in replacing all the rubber parts?

Thanks
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About the same vintage as mine and a few hundred more hours. But remember, TBO is not a real number.

Friction torque at the prop says you have the slipper clutch. Mine doesn't.

If the floats are still floating, fine. But they may yet decide to start to sink (engine runs rich). They are stupid easy to replace. Just expensive to buy.

One service center is estimating $800 for a gear box inspection. Of course, you would have to pull the gearbox and ship and it assumes gears, clutch, etc. are still good.

4 Stroke Gear Box Services - ROTAX Repairs - ROTAX Engines & Parts

Advanced Powerplant Solutions Online Store
www.advancedpowerplant.com www.advancedpowerplant.com
(They did a nice job on my water pump)

Personally, I don't get excited about replacing all the rubber on schedule. Cost depends - for example: actual official 17mm coolant hose is $100 per meter from the above source (you need 2m per engine), 5/8" coolant hose from an automotive source is a lot less (a bit tight, but works).
 
Capt. Geoffrey Thorpe said:
One service center is estimating $800 for a gear box inspection. Of course, you would have to pull the gearbox and ship and it assumes gears, clutch, etc. are still good.
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Hi everyone.
That would be nice.
Here are some details from one recent invoice:
Send Gearbox for reoccurring inspection $390.00
Ship Heavy box Insurance $200.0
Gear box repair $2,600.00...
 
Also keep in mind that an overhaul is only slightly cheaper than buying a new engine and you’re probably better off just buying a new engine at TBO…
 
Or 500 hours after tbo if everything is running good.
 
No rubber replacement in 12 years. No gear box inspection yet, at 1000 hours. Owner says shop told him that the gear box inspection isn't needed, they never find anything wrong. They do test the torque for clutch operation each year, saying that if that is good there is no need for an inspection. Seems to me that there are more parts in there than just the clutch that might benefit from being looked at?
I personally don't think the condition of a hose can be determined from a look at the outside, seems like 5 years is overkill, but should certainly be done by 10 years?

What happens in gearboxes if the idle speed is too low, I think I have read that 2000rpm is minimum?
 
Wagondriver said:
No rubber replacement in 12 years. No gear box inspection yet, at 1000 hours. Owner says shop told him that the gear box inspection isn't needed, they never find anything wrong. They do test the torque for clutch operation each year, saying that if that is good there is no need for an inspection. Seems to me that there are more parts in there than just the clutch that might benefit from being looked at?
I personally don't think the condition of a hose can be determined from a look at the outside, seems like 5 years is overkill, but should certainly be done by 10 years?

What happens in gearboxes if the idle speed is too low, I think I have read that 2000rpm is minimum?
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If you're looking at an EAB or ELSA then the seller or you the purchaser are of course free to do whatever you like with regard to engine maintenance. If it's not EAB or ELSA then it can become a bit more gray. For example, the RV-12 Maintenance manual says this in the Condition/100 Hour inspection chapter: "Refer to the Rotax line maintenance manual for proper inspection procedure for engine and components supplied with engine." The Rotax Line Maintenance manual specifies rubber hose replacement at 5 years and gearbox inspection at 1,000 hours, so if those items aren't performed IAW the maintenance manual, is the aircraft legal to fly? Whatever airframe you're looking at may or may not have similar language...

Regarding the gearbox inspection, post #11 would seem to indicate that at least someone has experience that there can indeed be something found wrong during gearbox inspection...

Regarding the hoses, I have seen reports all over the place from someone finding a hose that was about to blow to someone that said their hoses were pristine and could have lasted 20 more years. I replaced my hoses a few months ago and most of them seemed like they would have lasted at least another 5 years. That said, on the RV-12, there are 10 coolant hoses and if one of them leaks/blows and the coolant is dumped there is a very short amount of time to get the aircraft on the ground before the heads will be ruined and then you may as well buy a new engine...

Low idle speed is hard on the gearbox. It is always prudent to idle the engine as high of an rpm as possible, circumstances permitting, by opening the throttle. The minimum idle speed is 1,400 rpm, but again, that's hard on the gearbox. It's also crucial to have the carburetors synced, if they're not, this too is hard on the gearbox.
 
Low idle is hard on the gearbox - you can hear it and feel it. Best idle, in my experience, is less about a number and more about what keeps the engine happy.

The rubber not being replace would ‘bother’ me, but more in the sense of “what else has not been maintained?”

I would not want to push beyond the 1000 hour gearbox inspection. Not something you want failing. At a minimum, it’s an area that collects lead if burning any 100LL. Even if the parts are not failing - it could probably use a thorough cleaning.

My guess based on the deferred items - your carbs are in need of a rebuild and rebalance as well.
 
I agree on the maintenance idea, what else has been neglected?
The thing about hoses is that you can't tell for sure until its off and you can inspect the inside of it. The log books look fairly professional, except that SB compliance is not noted as compliance, just an entry saying a part was replaced. Log books show weighing of carb floats, new fuel pumps and fuel lines, checking clutch breakaway torque.

A friend has a saying about experimental "why do it right when you don't have to".

To me, the gear box inspection is not optional, and after 12 years hoses and carb sockets are not either.
 
Congrats! Rotax are a great engine, but like any - they need to be maintained correctly. I heard someone say once that the primary cause of failures in Rotax engines is that they get maintained improperly by people who don’t understand them.
 
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