YS History

These are all evolutions of the same motor I cover what I know about them in the order they came out. For the most part each iteration had more power until the 120SC.

120SF--Original YS 120 4 stoke

120SF--Big valve this increased performance a little bit.

120AC--a hopped up version of the 120. Had the air box on the back. This was the real power house of the 120's. It made huge mongo power. The main issue with the 120AC was its weight. It was about 2ozs heavier than the others...both because the motor was beefed up structurally and it had the extra metal of the Air chamber. This motor was really the work horse of the pattern community for a long time. The Dr J's and up through even the Sequels and Prophecy were mostly flown with this motor. But as I said before weight was an issue.

120NC and 120SC--This is where YS branched out into the sport modeler market. The top of the line competition pilots gravitated to the SC for its increased power over the 120AC. This motor also reduced weight. The air box was now under the valve cover like most of the motors today....A little less boost than the AC but if run properly more power. The NC was basically the same motor but detuned a little not so hopped up that life was superb on them. They were the Non-Chambered motors. Many of the non FAI pilots ran this 120NC motor for a long time as it was more beans than the SF but not by a bunch and had similar docile operation qualities.

120SC became a motor that was tough on parts. The piston was lightened beyond belief and the motor was running on the ragged edge but making huge power. This is the motor than many people got upset about as it was not the easiest to run....Backfire and bam you just bought some parts. If it was treated well and never run lean the SC was a great motor...But run it out of gas, Yep thats a lean run and it would bark, talk, spit and break things left and right. It was really a motor aimed at the top guys in competition that had lots of experience running the YS motors. In the mean time FAI and Pattern rules stepped back from the 1.20 size limit and removed all engine displacement limits. This gave Yamada the opportunity to increase the displacement of the motor in order to get more power rather than work on the latest hop ups to the 120's. The reason the 120 had so many versions was the desire for more power more power....and YS gave it to the modelers in the form of high performance versions of the same 120. Now the 140FZ was born. More cubes always is an advantage.

140FZ--This motor was equal in and in most cases more power than the 120SC but since it did it with more cubes rather than the high compression hop ups...It became a honey. Somewhere along this time frame the air bleed throttle barrel screw arrived...I think on the SC's first then it carried over the 140FZ....Now all motors with the air bleed screw on the throttle barrel were designated FZ so they shortly released a 120FZ basically an NC with a different throttle barrel. The 140FZ was one of the most docile and easy to run YS motors of all. It was not overly compressed would run a long time and make great power.

120FZ similar to the 120NC as it was a Non Chambered motor but it had the throttle barrel bleed screw and the backplate YS motor mount. The new look of the YS motor mount was less functional in terms of the performance of the motor. Sure pistons may have changed along the way and as always YS tinkers with better parts...but most all the parts are interchangeable on the 120's...The AC is the one with the most physical parts changes.

140L Released about the same time as the 120FZ maybe a touch earlier was the Limited edition motor that stayed with us for 4 years+. This motor used some of the hop ups that Yamada learned on the 120's to give some more beans to the 140FZ....Basically this motor was intended again for that top level F3A competition flyer. A new Motor mount from YS had similar principles to the Hyde mount. The 140L was designed for the competition segment and the 120FZ was the sport guys motor or the pattern flyer on a budget.

Then comes the 140DZ....new fuel injection system. Means Huge power increases...all of the other power increases were small..150-200 here 300 there. The Dingo broke the mold. Changing the the way cold fuel is injected into the motor and the lack of the pressure system that was a YS trademark....the motor was truly a revolution in YS motors.

Once the DZ came to favor the 140L started loose its luster as the top competition motor so YS in the USA released the 140FZ Sport...Basically its a 140FZ with some of the power improvements of the 140L like a bigger carb and more robust piston. This motor was targeted at that Sport crowd and was priced to replace the 120's. Now the Sport guys can get the 140 power and performance for the price they paid for their 120's.

So the current crop is the 140DZ and the 140Sport. On the future horizon maybe a 160DZ. Some top pilots have been testing the idea in a new motor...But I don't know the details on any release info...My guess is late next year.

I know this is a little too much info but I think it covers the YS evolution...perhaps there are some other major changes in this mix but I can't think of them right now.

Troy