I just got a notice that the newer version of the Stalker 51RE is finally ready.  Earlier this year Stalker decided to take what I and many Stalker users feel to be one of their best offerings and make some changes to it.  Nothing was done to the layout of the interior of the engine itself.  The primary change was in the muffler and its attachment.  Instead of the usual plug in muffler with o-rings for seals, Stalker threaded the end of the muffler and the exhaust outlet on the case so that the muffler now screws on.  Below are some pictures of the set-up.  Also a new lighter all metal muffler is offered as opposed to the CF tube muffler used on the 51 in the past.  the new muffler is about 9g lighter in weight and I think it is very slightly less effective at noise reduction but slightly better powerwise.  In June of this year I was able to get one of the pre-production engines and sent it to Norm Whittle in Salt Lake City as he was looking for one for his new profile project.  Norm has been good enough to keep me posted as to how the engine performed and if he had any problems with the new muffler arrangement.  I think we were both a bit apprehensive with the new mounting system and because the system was basically untried we figured some glitches would come up.  With the muffler fully screwed on the exhaust outlet points down when the engine in in the inverted position.  First question was what about if you want to side mount the engine as Norm wanted to do.  the only answer is to put some shims on the threaded portion of the muffler to space it further from the case when installed.  Anyone should be able to figure that out.  Stalker said to keep the muffler tight the user should use Teflon tape or some sort of thread locking compound.   Neither of these options had a lasting effect and the muffler continued to come loose after 5 to 6 runs.  This did not please me as I have half a dozen of the engines on order and they are all spoken for.  Norm fought the problem for a while and finally decided to use JB Weld and permanently glue the muffler on and then cut the header in the middle and use silicone tubing to join the two.  There are some pictures below.  I've been in contact with Stalker and Oleg is going to come up with a fix to the problem.  I suggested drilling the assembled unit and tapping it so that a bolt goes through the threaded area and keeps the muffler from being able to twist.  We'll see what Ukrainian engineering comes up with.  The only downside to the arrangement that I an see is that the engine/muffler unit needs to be installed as a unit making maintenance of one or the other a complete removal from the airplane operation.
While I'm talking about Stalker engines, I've had some people ask me about some comments that Keith Varley made about the engine run on my new model with the "low timed" 61RE.  This engine was often referred to as the 61RE 2-2 engine.  I'm not sure exactly what a 2-2 engine is but anyway I can tell you that the timing on the engine is set at 110/130 as opposed to 120/140 for the standard 61RE  This is done by slightly lowering the piston liner assy. by milling the top of the case.  The fit of the piston liner has to be altered slightly as the piston has to travel slightly higher into the liner.  The engine still has a definite 4-2-4 break pattern although it does it at a slightly lower RPM and the switching seems more suttle to me.  This engine is quite a bit heavier than the LT or the LS versions and I think that it runs much smoother due to the heavier case.

If the head of your engine is anodized you have one of the older engines.  I don't doubt that your engine does indeed have those numbers.  The table on the old Modusa site is somewhat out of date. The timing numbers on most of the engines was changed in 2002 or so.  All Stalker engines up to the 61 RE & SE have a 120/140 timing with the 61RE also available in a 110/130 timing.  The 61LT also uses the 120/140 while the 61LS and the 66LS uses a 115/135 timing.  The 66RE is simply a bored out 61LS.  The 76 and 81 RE's use a 110/130 timing.  I know for a fact that the 61RE I have with the 110/130 timing has had the sleeve lowered to get those numbers because the maker told me so.