Rotax 912 Overhaul

[Paul Willett]

Has anyone had a 912ULS overhauled? What exactly is involved? What would the cost be? Who does it, apart from Bert Flood?

 

Why I am asking so many questions?!

 

 

[Guest byteboy]

I attended a class at Sun n Fun put on by Phil Lockwood in reference to the 912. It's just a little more to purchase a new engine then overhaul it.

 

Roger

 

 

[Guest Guest]

Howdy,

 

Well that's not entirely correct - a new 912s is around $17k. Bert Floods is a factory approved overhaul facility. For GA use you'd need a full "factory" rebuild or replacement, possibly why Roger is confused. Bert doesn't do "factory" rebuilds as such, but they will trade. A used 912 80 hp brings anywhere from $5k-$10k.

 

It could cost anywhere from $4k - $7k+ to overhaul a 912. It all depends on how many hours it's done, how it's been treated, what fuel it ran on and what's wrong with it if anything. As a comparison, a Jabiru 6 cylinder overhaul is around $6k.

 

If you're talking 1,500 hours and the first overhaul, then you'd be looking probably at a top-end only plus the gearbox. I know a gentleman who did his himself for a fraction under $2k including the gearbox, however not including labour. Bert has many engines that have clocked well over 3,000 hours and haven't had a bottom end overhaul and he's suggested that they could easily run to 5,000 hours.

 

Give Bert a call and he'll fill you in or talk to "Wal" in the workshop; 912's are his life!

 

 

[Paul Willett]

Thanks,

 

my 100HP 912ULS only has 140 hours on it, so we are talking probably 10 years away at current useage - it is more a budgeting/residual value exercise, and learning what normally needs doing.

 

 

[Guest micgrace]

Hi

 

I'd say at 3000 hours a pull down of bottom end would be mandatory. Crack test of crank and rods plus new rod bolts. Plus new barrels/pistons, bearings plus regrind?. Would pay to be safe at these hours. It wouldn't be THAT expensive compared to new price, esp as the heads would be off anyway.

 

Just my opinion, Micgrace

 

 

[Guest ozzie]

i have been listening to some of the engine rebuilders in the states, and they have said that the price of rebuilding Rotax engines are quite expensive when compared to the price of a new engine. Theses people have said that rotax would prefer to replace rather than rebuild. it would be interesting to see the difference in prices to rebuild such a high time engine. Ozzzie

 

 

[Guest micgrace]

Hi Ozzie

 

If you had to replace the major component, crank, that's expensive. I'd be getting another engine.

 

I'd do a crack test on it first before getting any components. I've had to track down a few second hand engines through the years when the crank failed this test to give up a good crank as the new price was insane (or unavailable).

 

This test is mandatory, not to be skimped on. Also the rods, plus a resize with NEW rod bolts.Also a main bearing bore alignment check isn't such a bad idea, not terribly expensive to remedy this problem. Line bore will cure (the reconditioner shaves the main cases, then line bores to size.

 

In fact some reconditioners believe a well used engine is much more dimensionally stable than new, as stresses from manfacture have been relieved by time in service.

 

Also, while down, you could do some work to get some additional reliability. Balance. Port match and other changes that are not done on new engines due to cost.

 

Just some info. Micgrace

 

micgrace

 

 

[hiperlight]

To put the prices of crankshafts into some sort of perspective:

 

an OEM 1972/3 Porsche 911E 2.4 crank is US$7.2k in California. Put freight and GST on that and your looking at about AUS$12k.

 

an aftermarket, two piece eccentric shaft for a Mazda 20B rotary is AUS$3.7k in Melbourne.

 

Once you engage in major rebuilding of engines it is worthwhile doing a parts cost exercise beforehand. Saves a lot of tears later.

 

Bruce

 

 

[Ultralights]

what are the comparable prices for second hand jabiru 3300 and 2200 and

 

rebuild costs, i am planning to buy a savannah ASAP and im

 

trying to compare costs of the 100Hp 912S or the Jabiru option.

 

 

[Guest ozzie]

One other thing that when considering rebuilding vs purchase is that even when the engine is rebuilt you may be relying still on many "old components". parts of the ignition/electrical systems for instance.

 

listening to advice from people who have as much expierience as them, i would take there advice and go new.

 

Other things to consider for outlaying a little extra for a new engine is warranties, and fresh accessories and maybe trade/sell your old core.

 

3000 hrs from a 912? thank you Mr Rotax, can i have another?

 

here is a story that will make you cringe.

 

The US Air Force use many Rotax engines, both 2 and 4 stroke on their drones. As the payload of some of these are worth millions, they, for instance with the 912's, replace them at 100 hrs. not rebuild but replace them. then under a supply agreement with Rotax they are destroyed and buried. (source: California Power Systems inc.)

 

 

[Guest Guest]

Rebuild costs for the 2200 Jab are in the latest Jabiru Newsletter at www.jabiru.net.auunder the newsletter section - april 2006 - prices have recently gone up for rebuilds.

 

 

[Paul Willett]

Ozzie,

 

That sounds like the American's all right - that blatant waste is a neccessary cost to protect the American way of life - which not co-incidentaly is one of blatant waste..

 

 

[Guest Guest]

Looks like I am in this situation now.

 

My engine has done 600 hours and has had the circlip from the sprag clutch go through the engine. The damage seems to be mostly to the camshaft gear on the crankshaft, as it is the softer one! It has a few teeth that are bent. The metal was cruched up and mostly ended up in the oil tank. There were a few bits still near the sprag clutch as well.

 

So now what. From your above posts I would think you would all suggest to go new but it is a young engine really.

 

Am I right in saying that the oil had to pass through the enine oil filter before it gets to the crankshaft bearings, and the big end bearings. If so, there should not be any issues with the bearings.

 

The engine also had a vibration in it that alerted me to this issue, but it may not be related. I bought the engine second hand in the a/c so dont know its full history.

 

The real concern as far as I am concerned is that I have to trust this engine, I'm taking my kids in what it powers !

 

I guess the answer is pretty obvious.

 

What do you think?

 

regards

 

Gtblu

 

 

[Guest Guest]

Just give Wal a call at Bert Flood Imports in Lilydale.

 

He'll pull it to bits, replace what needs replacing and charge you for the time and parts. He won't over charge and he will give you what you need.

 

Potentially your aircraft had a prop-strike, however for that damage to occur it was probably a significant one.

 

 

[Yenn]

Seems a bit stupid to me to scrap an engine at 100 hours. I would expect more problems in the first 100 hours than in the next 400.

 

Ian

 

 

[Guest Guest]

600.. not 100

 

 

[Kade]

i have recently acquired an XT912 airborne trike , it was built in 2005 with a rotax 912 UL ser#4407101 installed. It has only accumulated 226hrs TTSN, it was last run some time in 2011, so it has been sitting idle for a while at a place well inland (like 2-3hrs drive north west of Melbourne where it is reasonably dry. however according to rotax it should have an overhaul, is there any alternative. Calendar time of 15 years runs out in 2019,

 

 

[Downunder]

Rotax have pretty much priced a new engine close to the price of a rebuild (parts/labour) so the general view is, it is not worth rebuilding.

 

Personally, I'd Just do a 5yr rubber replacement, 100/200 hr service and take it from there.....

 

Oil filter inspection, leak down comp test.... Barrels are nikasil lined aluminium so don't rust.

 

Be wary of dropping too much "coin" into it as opposed to a new or another second hand engine.

 

If you wanted to play it on the absolute safe side, buy a new engine and flog it as is.....

 

I hope you got it for a very low price. I've seen some 912 XT's almost go for the price of the engine alone...

 

 

[bexrbetter]

is there any alternative.

Pull pugs and first turn motor over gently with small movements back and forth to feel for and remove and corrosion spots on the bore and crank.

 

The difficulty of moving past those points from it's original crank position as found, if any, is a good indication of what you're up against.

 

If feels ok, drain the oil and fill with diesel and turn it over for a bit on the starter, drain to flush old crap out.

 

Further to other rubber deterioration, you may need to do valve stem seals, personally I would whip the heads off, de coke everything and do them along with a valve lap. Gives you a chance to inspect the bores and feel for crank problems through the piston.

 

 

[facthunter]

There's some funny comments here on this engine. It's got Nikasil Bores. They don't rust. There are NO rod bolts. the big ends are full circular and the crankshaft is pressed together. (That's a problem for the ordinary workshop). Normally they "SIT" well without special storage precautions compared to most other motors. The main place to look hard is the exhaust valve stems/ guides due to being red hot in service sometimes they corrode when sitting. Nev

 

 

[Yenn]

I think a few have commented here without knowledge of the 912, as pointed out by Facthunter.

 

Use a bit of discernment in taking advice here.

 

Comparing the Rotax with Jab cost wise is comparing apples with oranges, but I must admit I have heard a very sad story about Rotax in the USA. Only one among thousands of engines.

 

 

[bexrbetter]

It's got Nikasil Bores. They don't rust.

As I've mentioned before, I did my first apprenticeship in a Yamaha motorcycle and Stihl Chainsaw shop (Rod Linden Yamaha, Frankston, Vic). I have torn apart hundreds of nikasil bore engines.

 

When they are left for years they build up a ring of gunk around the union of the metal rings, piston crown and bore, probably galvanic corrosion from dissimilar metals, but I ain't a metallurgist.

 

When, and if you can free the piston, by the forth mentioned rocking back and forth, it varies what is left, sometimes nothing noticable other than a discolouration, sometimes pitting and sometimes throwaway if a partial ring of the electroplated lining has been eaten away. Where the problem is in the cylinder of course has a large bearing on the decision making.

 

Cylinders we felt usable, we ran a rigid diamond stoned hone very lightly to deglaze which could also showed up flaking and other oddities.

 

The same applies to roller cranks, re; corrosion and pitting on the crank pins, rollers and conrod. That of course is a bit more serious. We pressed our own single cylinder cranks, but always sent out multi cylinders cranks.

 

 

[facthunter]

I've actually seen a few 912's left for a long time and then checked. They usually only need to look at the exhaust valves. I wouldn't split the crank as you can feel the (plain) bearings and they can have a problem with the press fit. Always check the bores even if just with a boroscope but they survive well. With steel cylinders you nearly always have corrosion and stuck rings. (in the grooves). Plenty of galvanic action with alloy and steel. Nev

 

 

[NinjaNate]

Gents...How long is considered long enough in your opinion that a Rotax 912 is left untouched to need to be concerned?.. is 12 months for example long enough to require more than just an oil change and good inspection (..particularly of rubber & hoses)?

 

 

[Downunder]

Gents...How long is considered long enough in your opinion that a Rotax 912 is left untouched to need to be concerned?.. is 12 months for example long enough to require more than just an oil change and good inspection (..particularly of rubber & hoses)?

My opinion (based on the aircraft being in a closed hangar)

 

I don't think 12 months is a grossly long time for a 912.

 

"Rubber & hoses".... depends on ultimately how old they are...but a feel and look to be sure.

 

Drop carb bowl & inspect fuel and residue, if any. Maybe remove plugs and turn over engine to purge old fuel through with bowls off. (Definitely replace fuel)

 

You should also get oil pressure on turn over too.

 

100 hr service would be due anyway....