Glad you asked that question!
With 500 hours on the engine I have replaced 2 old type fuel pumps. Now have the new type, so far it seems to be working fine. One of my carb floats stopped floating
so I replaced with new one. Other than that everything has been working great. I really like the engine so far. However if my engine fell into the serial number group with the crank shaft SB then I would not be a happy guy.
Things I like about the engine.
Sips fuel.
Power to weight ratio, 100 hp, out the crate weight 122lbs.
No magnetos.
Auto spark plugs.
50 hour oil change.
Runs on unleaded gas even with ethanol.
Starts super easy.
Really like the web site with all the great info including the videos for do-it-yourself types like me
Feel free to add to this list!
That being said I think Rotax should, for free of charge, fix all the engines that fall into the SB. All engines have occasional SBs. It a part of life. Doesn't seem one is any better that the other one. The RV12 was designed around the Rotax. Adding a heavier engine will change the aerodynamics of the airplane. I'm conservative and don't want to be a test pilot so I'm sticking with the stock setup.
I think that's why the RV12 has been so successful. I would say less than 1% have a different type of engine on it.
Pardon me while I rant a little
The RV12 kit was released for sale in April 2008. Almost 800 serial numbers having been sold. We are getting close to 300 completed flying RV12s in 5 years. A long life span was considered durning its design as well as a perfect harmony in over flight characteristics and performance for the average pilot. Although it can be built as an EAB it really wasn't designed to be built far from its original plans. So when changing to an alternate engine consider the weight you will be adding to the nose and how that will effect the flying characteristics of it. Will you do spin tests with this heavier engine? Also consider there would be nothing worse than the 1000 hours of you personal labor sitting all bent to heck in the corn field at the end of the runway not to mention your personal well being as you exit the plane in that field. This all being said we are taking about an experimental airplane here so if you have the experience and support network to change to something different safely then good luck in your endeavor.