Engine case studs

I guess nobody else has had this problem.

Maybe Rotax wizard or an experienced guru can chime in?

The correct way is to take it to a independent Service Center, iSC, as this is only found in the overhaul manual.  That bolt is put in and attaches to the back of the stud collar nut on cylinder number 1.  This requires the cylinder number 1 be removed and then special torque sequence done, it involves angle torque.  (the bolt with the leak is a case bolt) Some of the early 2006 to 2007 new generation crankcases had issues with the collar nuts.  The best thing to do would be have the iSC split the block, replace the collar nuts, and reseal the crankcase.  This can only be done by someone trained and with the correct manual.  These bolts are stretch bolts and have to be replaced, not reused, if they are removed) If this is indeed a 2006 to 2007 block that is what I would recommend.  In recent years they even changed them again to a different thread pitch.  All the inner studs in the crankcase were changed and the collor nuts.  The clamp forces are very high.  Indeed if the stud kit has to be updated and the new kit installed by the iSC, they will have to do some machining on one just behind the oil pump as it now uses a special nut.  

It's complicated. 

You might be OK if the case serial number is out of that range, find that between the push rod tubes on the crankcase.  it will be stamped into the block.  Perhaps start with that so we can be sure. 

Cheers

Thanks Rotax wizard,

My case serial number is 061157

The engine serial number is 5647127

The previous owner's logbook worryingly shows that a new camshaft (due to metal shavings found in the oil filter) and lifters along with new main and big end bearings and piston sets were replaced 500 hours ago. No mention of replacing any case bolts. I question the accuracy of the logbook entry as I don't believe they would have been able to replace the big end bearings without replacing the crankshaft and if they replaced the crankshaft, why wasn't this mentioned in the logs. I am not sure if the organization that did the work is an ISC or not, I think Australia only has one (Bert Flood) but it wasn't them that did the work.

Maybe I have more problems than just a minor oil leak!

Hi Murray & RW,

I commend your diligence Murray  however before proceeding further (many $$ involved) I think you should ask yourself, RW & Roger Lee - is this a critical or aesthetic problem? ie if left alone, is there any risk to engine function/aircraft safety ?

It may not be the norm in aviation however almost every ground based engine, with more than a few kilometres/hrs of operation, will have a few weeps without any significant impact on function.😈

Hello Murray

Your serial number shows it was in the range where the issues may occur.  To replace the cam would involve splitting the crankcase.  The studs in that case should be replaced whenever it is split due to the type of stud material.  It is perhaps as Sean said, perhaps this is minor and may never be an issue, it would be your call on that.  The crankshaft and bearing shells on a low time engine were not likley replaced as you have noted but that part would not be a concern to me.  The way the dry sump works almost 100% of any debris would be retained in the oil tank, oil cooler and oil filter.  It is highly unlikely they would have circulated into the main bearings and crank rods.  Indeed the fact is is running 500 hours later suggests that much is just fine. if it is of concern to you perhaps contact the new owners of Bert Flood and see what they might recommend and cost. 

Just as a note, the range is 06.0010 to 07.5001 if there are any issues as I noted before. 

Cheers