Super Tigre 90 question

I have recently aquired two new Super Tigre 90 engines. Both engines have little or no documentation in the boxes.

I would like to know the difference between the two engines

One is a S90 R/C will the other is a S90 K Ring R/C

Both engines are ringed.
The carburetors are different between the two.
The S 90 has a cast but machined outside head (round) while ihe S90 K is cast only.
The S 90 has a smaller muffer and is attached directly to the engine while the S 90 K Ring has a large muffler and is attached to the engine through a machined aluminum transtion.

I would like to know if they are the same engine just different vintages or whatever.
I have not been able to find any documentation anywhere to support the differences between the two.

Any experts out there that might help me?

I look forward to any reply.

The S90 is of the earlier time when ST really produced superior engines, maybe not in total output but reliability and very long life, IMO, make them the best of the best.
The S90K is also a great engine, but a tad heavier and the modifications to make it look, shall I say, "cool"?
The S90 K muffler arrangement is a definite plus as one has more options with the mounting. However one can get the muffler too snug on the inside and create problems that will be attributed to the carb. With the alum. tube too close to the muffler wall, a lot of transition problems sometimes happen, and most fumble with the carb. which doesn't help. (I have purchased a number of STs off eBay that I suspect the owner could not fix, but are excellent engines)

If you have needle problems with the older carb. Harold Higgly products has needle valves for that carb. They break off very easily.
In any case you have a couple fine engines.

Nope! The China motors are G's.

I have the same two and wouldn't be concerned about the differences. The round head one come before the 'square' head one.
Both work fine. Since they are in different types of planes I can't really tell if one is any different from the other from a performance standpoint. One is in a big Beaver on floats and uses a 14 x 6 prop;
the other is in a low wing sport job and uses a 12 x 9. One caution is to make sure they have good cooling. The case is small and in a tight cowl they can over heat and quit. I haven't run the newer one all that much but the older one has been exceptionally reliable. The needle valve broke off about five years ago and hasn't been adjusted since. YMMV

John Hawkins - From Canada's Atlantic Coast http://rcalbum.rchomepage.com/Home.html

They are now produced in China. You might have a Chineese one and an
Italian one.