Hello Guys,

Sorry for my english, I'm from Mexico. I bought this engine from a friend of mine and I've had it for a few months and I can say that this engine is one of the greatest engines that I ever had, it is extremely reliable and powerful. I'm running it with a master airscrew 16x8 and it spins it like a lightning. I don't have any problem with the performance of this engine, but I have some questions about this engine.

Here are some questions of this engine:

1. Like other people I actually don't know which engine I have, In the left side it only saids YS F-120. I can assume that this engine can be SF or NC because my engine does not have low speed needle, and it can't be the AC because this engine doesn't have the air chamber.

I can also assume that this engine is the SF because the carburetor gasket is like the one that appears here:http://www.centralhobbies.com/engine...YS120SFEX.html and the carburetor gasket of my engine is different from the NC, but, if I look closer the diagrams of both engines (SF and NC) there aresome thing that makes me doubt. The number one is that the valve keepers (11) in the SF diagram are different than my engine, in the diagram there arein<font face="Arial" size="2">C-Ring shape, but in my engine are like in the NC diagram (Spring Retainer Clips). and there is another difference; in the SF diagram the Wrist Pin Retainers are like a c-shaped wire and in my engine the Wrist Pin Retainers are like in the NC diagram (plastic cylinders).

So, in this moment I'm confused. I already bought and installed the gasket set for this engine (the gasket set is like in the SF diagram).

2. Last weekeng I was flying my Showtime 90 with this great engine and the exhaut pipe fell and was lost. This engine seems to have muffler (like in the NC diagram) because at the end of the exhaust pipe has threaded, but again, in the SF diagram, it only appears an exhaust pipe without muffler. So this thing makes me feel more confused. Here is another two questions, which of the two exhaust systems is the correct for my engine?. I really want to put in my plane a smoke pump, so again, Which one is the right exhaust for my engine?

3. I don't have the instruction manual for this engine and I have not found it, could you please send me the instruction manual?

Thanks in advance,

I remain at your disposal

Juan Pablo =)

P.S. I will send some pictures of the engine


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That is a 120SF. The short snout between the pushrods and the thrust washer, lack of a horizontal rib between the big part of the case and the front bearing housing plus the big thrust washer The valves may have been replaced with a newer version at some point which would explain why the keepers are different. Also the exhaust port thread is the same from the YS 91 - 1.75 so any muffler or pipe could be used there.

Thanks a lot for responding, I really appreciate it,

So, do you thing that the valves are maybe from a NC engine? or maybe the complete head is different?

Another question, what do you recommend to do to prevent the exhaust from falling? use thread locker, Teflon?

Could you send me please the instruction manual for this engine

Thanks a lot

Juan Pablo<br type="_moz" />

Juan it could be a new head assembly or just new valves. As for the exhaust falling off all mine are just locked in with a lock nut.

PM me your email address and I can send you a 1.20AC manual which tunes the same way.

PM sent

Thanks

Juan Pablo