Cost to overhaul a 912?

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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shasta
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Cost to overhaul a 912?

Postby shasta » Mon Oct 10, 2011 2:19 am

Here is a question maybe some of you Rotax mechanics can answer, as I seem to be getting many different answers reading online. I was wondering about what it would cost to overhaul a 912ul or a 912uls. I know this can vary greatly but I was curious about what to expect for a major.

I know most of the 912's are a long ways away from needing it but I have seen a couple of airplanes that are getting close and one very nice one that was at 1600 hours. I am just trying to get an idea about what I should be setting aside for an engine fund if I decide to purchase something with a 912 in it.

Thanks

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912 rebuild cost

Postby roger lee » Mon Oct 10, 2011 9:23 am

The cost to do an overhaul on a 912 is approximately $12K and that needs to be done at a distributor that has someone qualified to tear it down to the case. I recommend to all my clients when it's close to sell their engine to an experimental owner for $8-$10 and then just buy a new one. The experimental folks aren't required to do a rebuild. (They should anyway, but) The cost is the same, but you end up with a zero time engine. The rebuilt one will never be a zero time engine again, but should last well into the 4K hr. time frame and more. Flight schools get to their TBO's much quicker than the private owner and that is a good way to keep engines rotated.
Roger Lee
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LSRM-A, Rotax Instructor & Rotax IRC
(520) 574-1080 (Home) Try Home First.
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drseti
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Postby drseti » Mon Oct 10, 2011 10:36 am

I agree with Roger. My engine is at 1045 Hobbs. When I get to 1900 I'll order a factory-new one, in the crate, for something like $20k (and am setting aside $10 per flight hour in my TBO Fund). At 2000 hrs, I'll swap the engines, and then advertise the old one on eBay Motors. I'll probably get $8k or so for it, assuming it's still running strong, so will be no worse off financially than if I had done a rebuild.

Brian Carpenter (Rainbow Aviation) takes this one step further. He recommends swapping out for a new engine at midtime. That way, you're staying outside of the up-slope in the maintenance curve. I guess you could get more for a 1000 hour engine than you could for a 2000 hour one, but this approach will probably end up costing you more. OTOH, if it keeps you from ever entering the wearout phase, your chances of an inflight engine failure are probably reduced.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS/PPC, iRMT
AvSport of Lock Haven
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shasta
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Postby shasta » Tue Oct 11, 2011 3:14 am

Thanks for the information. I guess that is pretty much what I feared it was going to be. I was visiting a guy who is building a kitfox and that was pretty much the advice he was given also. When the engine was about done just pull it out and sell it.

I just was wondering as I saw an ad on Barnstormers for a guy who would do rebuilds on 912-914's for $1800 plus parts. Also another ad, a few weeks ago, was giving a 6k rebuild credit for a 912uls that had 1600 hours on it. It was an AB Kitfox Vixen. He did say it did not need it but he would lower the price to cover the cost of an overhaul. I was just hoping it would only be about 6k but I had heard the 10-12k figure before too.

Anyway thanks for your time. I am just trying to get as much information as I can before I make any decisions. Nice to have a forum like this to ask questions.

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Postby Jim Stewart » Tue Oct 11, 2011 8:49 am

Back when I bought my CTSW it didn't take me long to figure out that selling a 3/4 run out 912 would be a better deal than rebuilding it. Now I suspect there will be a glut of run out engines on the market when it's time.

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Postby drseti » Tue Oct 11, 2011 9:05 am

Jim Stewart wrote:I suspect there will be a glut of run out engines on the market when it's time.


"Run out" is a relative term, Jim. For flight school aircraft, TBO is regulatory. Since mine has complied with the service bulletins to raise its TBO to 2000 hours, I will have to major or replace it then, regardless of condition. But, for those aircraft owned and being flown by individuals, it's not the case. So, unless the plane is in commercial service (mine is :( ), overhaul is done on condition, not Hobbs time.

From a practical standpoint, properly maintained Rotax 912s and 912uls can be expected to go 3,000 to 4,000 hours, safely, without major maintenance. That is, assuming that the gearbox and carb overhauls are done at proper intervals (and the 5-year rubber replacement is complied with).

So, how do you know when your Rotax is run out? You could wait for it to fail in flight, of course, but I'd think that monitoring compression, doing spectrographic oil analysis, and cutting open oil filters at every oil change would be a better approach.

As I recall, Rotax ran a competition last year, to find the oldest 912 still in service. They had quite a few entries that were still running strong at over 5,000 hours. Does anyone know what the winning time was?
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS/PPC, iRMT
AvSport of Lock Haven
fly@AvSport.org
http://AvSport.org
http://facebook.com/SportFlying

shasta
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Postby shasta » Tue Oct 11, 2011 2:18 pm

I am sure there will be a glut of high time engines here in a few years. I think that will be great for the homebuilt guys. Let’s face it, not many years ago two strokes, with 300 hour engines, were the norm. I know I would rather take my chances with a high time 912, which I was monitoring closely. If you figure you can get another 1000 hours, before you need to do anything, you would probably be much better off than using a 582 financially. It should be more reliable, get better fuel economy, more power and you are going to end up rebuilding the 2-stroke a couple of times. Most of the information I have seen shows the 912 being much cheaper than the 2-stroke anyway when you take a 912 at 1500 hours and a 582 at the same number. Fewer rebuilds and so much less fuel and oil.

I was bored last night at work and I emailed a guy about rebuilding a 912. He wrote me back today saying it would be about $1500 in labor. He never did give me an approximate figure only saying that he had legally done several, and that he did not replace parts that did not need it. He basically wanted me to give him a call, which I understand. I am assuming he meant that he usually did not replace the crank. I did look at a parts list online and see that a new crank is about $4500 add pistons and gaskets you are about $7000.

I don’t know much about all of this other than what I have read but I would guess in a few years we might see a secondary market for remanufactured parts. You guys running S-LSA’s will most likely always want new engines or complete rebuilds with new parts but lots of guys flying cheaper AB’s would be happy to have remanufactured parts for their non-certified engines.

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Re: Cost to overhaul a 912?

Postby acensor » Mon Dec 23, 2013 9:05 pm

Regarding the post mentioning one offer to rebuild a 912 for $1500 plus parts:

When I look my light sport mechanics course in Corning California the instructor,
Brian Carpenter (Rainbow Aviation) , pointed out that there is are different levels of rebuilder quality and performance that roughly correspond with price.
At the very top is the very expensive factory rebuild which allows you to call it a zero time engine.
At the bottom price are some folks that are borderline, or below borderline, of ethics.
They will do such things as during the rebuild take OUT the best least worn components of your engine and put them into their inventory and replace them with cheaper components that they took out of salvage engines, etc, that are just over legal tolerances.
In between, he presented, that there are a full range of rebuilders ranging from top to bottom tier.
Brain actually gave a chart on the blackboard of cost-of-rebuild vs what to expect the type of rebuild you'll get for that price.
I could probably find that price vs. quality chart if I dug in my old class notes.

In short, his take, probably generally valid, was "you get what you pay for" on a Rotax rebuild.
This is not to say everyone offering a somewhat lower rebuild price is incompetant or borderline dishonest. But I bet Brian's take is basically correct.
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designrs
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Re: Cost to overhaul a 912?

Postby designrs » Thu Dec 26, 2013 12:50 pm

acensor wrote:At the bottom price are some folks that are borderline, or below borderline, of ethics.
They will do such things as during the rebuild take OUT the best least worn components of your engine and put them into their inventory and replace them with cheaper components that they took out of salvage engines, etc, that are just over legal tolerances.


That is the absolutely most appalling business ethics practice that I have ever read about in aviation. It's like charging customers to put rat poison in their coffee. It's just evil! Geez!!! :cry:

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Re: Cost to overhaul a 912?

Postby designrs » Thu Dec 26, 2013 12:53 pm

I like Paul's suggestion. Take the best care of your motor, monitoring everything for long engine life, then sell the motor honestly to someone who is willing to deal with the TBO / maintence issues, and get yourself a new motor.
- Richard

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Re:

Postby designrs » Thu Dec 26, 2013 12:56 pm

drseti wrote:That is, assuming that the gearbox and carb overhauls are done at proper intervals.


Can you please elaborate about this Paul? I am unfamiliar, especially related to the carb overhaul.

acensor
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Re: Re: carb ovehauls on Rotax 912

Postby acensor » Thu Dec 26, 2013 3:06 pm

designrs wrote:
drseti wrote:That is, assuming that the gearbox and carb overhauls are done at proper intervals.


Can you please elaborate about this Paul? I am unfamiliar, especially related to the carb overhaul.


If I remember right Rotax (or at least many Rotax mechanics) recommend a carb overhaul at about 200 hours. There may be a time (such as 5 years) recommendation too.

We didn't know about that recommendation on our 912ul and it was at about 13 years and about 600+ hours before we the message go through to us and we had ours rebuilt.

In most(?) cases degenerating parts in a carb overdue for rebuild would not IMO cause really dangerous consequences -- things like loss of some power, increase in fuel consumption, and/or somewhat rougher running...roughness that doesn't fully clear up with a proper carb synchroization. In other cases of a failure if one carb quit the engine would of course be running on two cyclinders and run EXTREMELY rough. Likely enough to shake the remaining carb loose and kill all power. If if not that, even worse, before the second carb was shaken off, the heavy vibration could rip off one or more motor mounts.

Before finally biting the bullet and getting the rebuild we did try squirting carb cleaner through them (air cleaners off, cowl open, engine running) and that did seem to help what we called "slight roughness at lower and some mid RPMs" a bit.

When we finally had our carbs rebuilt by professionals down at Rainbow Aviation (Corning California) , and off course then resynchronized, the change was dramatic. We could hardly believe how much more smoothly, and quietly it runs through the whole RPM range.
It was like having a new engine.

Our excuse for not realizing how much it needed a carb rebuild is that when we got the plane (used) it ran with a certain level of roughness at certain RPM. So we had no standard to compare it to how it SHOULD have been running if all was right.

As for the condition of the parts in the carb despite the long over due rebuild.
Clearly it was overdue, but not as bad inside as might've been expected.
No varnish/deposits (probably because of our use of carb cleaner).
The diaphrams still in good condition. Looked like they could have gone another 10 years.
There was a bit of corrosian on the bottom of one of the bowls which was removed.
The jet and needs had very slight evidence of age/etching.
The worse thing was that the some of the O-rings were brittle and probably not sealing as well as they should. One O-ring was slightly unseated. And they determined that the richness setting on one jet was not at factor standard spec.

So how long should you go before a carb rebuild? Your call.
I'd guess not more than 400 hours, or if other symptoms indicate (such as roughness at any RPM above 2000 that does not dissapear after a proper carb sync, or spark plugs indicating too rich or too lean running, or noticable increase in fuel consumption.

The rebuild kits are not cheap. Expect to pay at least $200 for parts. There are different levels of rebuild kits with the kits that include more parts (you don't necessary have to replace ALL parts at every rebuild) costing even more.

HTH.

I am not a carb expert or a mechanic. These are just my experiences and unprofessional opinions. Do your own homework. ;-)


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designrs
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Re: Cost to overhaul a 912?

Postby designrs » Thu Dec 26, 2013 3:19 pm

Most interesting and informative. Thank you!
- Richard

roger lee
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Re: Cost to overhaul a 912?

Postby roger lee » Thu Dec 26, 2013 3:27 pm

Rotax carbs don't get rebuilt after 200 hrs. There is no time limit in any Rotax manual or SB to rebuild a carb. The Line maint. says this is only an inspection at 200 hrs. Now if you had only 200 hrs. in 10 years then yes they need rebuilding due to rotting of parts that can cause leaks. If it is only 200 hrs in 2 years and up to 800 in 5-6 years you'll most likely be fine to that time. I'm basing some of this on that most LSA owners seem to be flying about 75-100 hrs. a year. ( I know there are some that are far more and less). If you only have 50 hrs on in 5 years then rebuild them. The "O" rings will be cracked. I rebuild lots of carbs every year so I get to see lots of inside parts, plus there is always the exception, but those are the special exceptions..

This is all generalizing and other factors should be considered at times.
Roger Lee
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LSRM-A, Rotax Instructor & Rotax IRC
(520) 574-1080 (Home) Try Home First.
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Re: Cost to overhaul a 912?

Postby designrs » Thu Dec 26, 2013 3:37 pm

interesting, I never thought of carbs as being a wearable part. 200 hours surprised me as well. That's not much time at 100 hours a year! Sounds more like a time thing (like 5 year rubber) than a hours-used issue. Thanks!


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