rotax 912S3 New old stock questions

600 hours or 5w years.

Make sure you do a good oil system purge. I do it twice to always make sure there are no large air in the system issues. The carb "O" rings will be dry and cracked and will most likely break apart if you try to remove them. I would replace all the "O" rings in the carbs and the needle valve. i just overhauled a set that were a tad older than yours and the "O" rings and the needle valve were bad. The internal metal parts of the carb should be okay since they haven't been in use and vibration should have caused wear.

If you have any questions you're welcome to give me a call.

Roger at 520-349-7056 in Tucson, AZ

Thank you Roger for your expertise. 

So do you have the manual for overhauling the carburetors?

As for the air purge in the oil system, I learned that topic during my ROTAX training, and as you said, it’s very important.

Thanks.

No Manual that I know of that explains how to do a PROPER carb overhaul. You can just do the "O" rings and needle valve. That isn't hard. There is a couple thing to look out for to make sure it's done right. I can explain them if you call.

I overhaul a lot of carbs every year.

All

The respective maintenance manual heavy, MMH, shows all the steps with the exception of the replacement of the throttle shaft removal for changing the shaft O-rings.  This is part of overhaul and not required until that point.  Normally it is discussed in a heavy program but there is no call out to overhaul in any of the scheduled maintenance items.  Scheduled maintenance is for replacement of parts based on condition or time (calendar time)  

Given the age of your engine you have bigger issues in being sure that the lubrication oils have not hardened and become dry over all this time.  Any humidity that may have been in the block could lead to some corrosion.  A very good inspection with a borescope is important at this point.  You should consider pulling one cylinder and using tghe borescope to check the crank, cam and any areas within the block you can see.  For the gearbox pull it off as an assembly and scope the gears and parts for any rust, there is no pitting allowance for the gearset so this needs a very careful check.  

Once completed carry out a very good oil purge followed by a test run.  The engine rubber parts, as called out in the 5 year time limited parts, should be changed.  I agree with Roger in that particularly O-rings in the carb will be subject to failure.  All these elastomer parts can off gas over time and normally become harder, this can lead to cracking as pointed out.  

Cheers