Power loss. Off field landing...

[Emory Bored 61]

There are only really a handful of Rotax heavy service centers in the country.  Some are better known than others.  I'm an Independent Rotax Maintenance Technician (expired) and I know almost nothing, so you better aim higher than that.  In your neck of the woods it would be hard to beat Lockwood in Florida or Leading Edge in Wisconsin.  Out here on the left coast CPS is well known and reliable as is  www.aircoreav.com    I know the owner at Aircore Aviation and I consider him to be one heck of a fine human being. You could do one heck of a lot worse than joining up at Rotax-Owner if you are going to own one.  They have all the service bulletins and what-not in a user friendly format.  

http://www.rotax-owner.com/en/support-topmenu/find-service

[EDMO 1078]

Does the Zipper mod work with the 80 hp?   EDMO

[Emory Bored 61]

Absolutely.  I would put the low compression, 104hp Zipper on the 80 only because it lacks the slipper clutch and you can run regular gas in it.  In my opinion, one also needs to use a light weight propeller like the Kool, Kiev, or Whirlwind on any Rotax 4 stroke to minimize sprag clutch problems.  Some believe there is a connection between the dreaded sprag clutch starting problems and the use of a slipper clutch.  It may help in a prop strike but barring that it only makes things less reliable.  Again, IMHO.    

[EDMO 1078]

Absolutely.  I would put the low compression, 104hp Zipper on the 80 only because it lacks the slipper clutch and you can run regular gas in it.  In my opinion, one also needs to use a light weight propeller like the Kool, Kiev, or Whirlwind on any Rotax 4 stroke to minimize sprag clutch problems.  Some believe there is a connection between the dreaded sprag clutch starting problems and the use of a slipper clutch.  It may help in a prop strike but barring that it only makes things less reliable.  Again, IMHO.    

BTW:  Although Whirlwind makes its own higher-priced props, Steve, the owner, has two factories, and the other makes blades that fit the Warp Drive hubs and are less expensive.    EDMO

[gregpro50 64]

What is a used 80hp 912 worth?  If we are talking about a $10k engine plus a $5k zipper kit I think I would rather just spend a few thousand extra and get a brand new 100hp.  But if we are talking about a $5k engine then the zipper kit makes sense.  I just don't have a feel for the market on these things.  Also there is the peace of mind knowing that the engine that cause a departure power failure at 250' is out of the plane.  I'm not sure what the value is of that.

[Emory Bored 61]

There are a lot of other factors as usual.  Engines made after 2006 have a stronger case design.  Prior to that some engines, particularly the 914s had fretting problems.  All horizontally opposed engines fret, including the legacy engines.  This means that on every power pulse the case halves fly apart a few microns and when they come together they cause wear on the mating surfaces. Rotax added a dowel or two and stronger thru bolts.  The ignition systems on earlier engines have an expensive service bulletin requiring replacement of the rotors.  If you look on the Rotax owners website you'll find a steady and significant list of improvements and changes through the years.  I've seen used prices ranging from $4500 to over $10K.  It depends.  The S engines are worth more than the UL engines.  The cost of replacement parts for Rotax are WORSE than Continental and Lycoming but unlike those engines they tend to go to TBO and beyond without significant work.  I worked on a 914 one time though that was essentially worthless after 450 hours.  It was parted out though and the owner recovered a pretty good chunk of change.  The case was shot, the rest of it held up pretty good. 

The 912ULS is no match torque wise for a Zipper engine.  There is no substitute for cubic inches. 

[gregpro50 64]

The FAA just closed the case.  It was classified as an 'incident' so everything afterwards worked out to the best case scenario.  I found them friendly, helpful, and good to work with.  I almost can't believe I just typed that.

[Emory Bored 61]

I've been working with FAA for 30 years or more.  I used to airboss airshows and had to be on my toes.  I was in charge of the wavered airspace and briefings of performers before the show.  The main deal is ordinary respect and telling the truth.  They catch you in a lie and you are flat screwed man.  

Cheers

Dan