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Just wondering

Old 10-30-2007, 05:38 PM
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Default Just wondering

I'm just curious. In the YS 4 cycle line, why is it that only the 110 (and 91's) have the air box on the back of the cylinder?
Old 10-30-2007, 10:17 PM
Troy Newman
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Default RE: Just wondering

The 120 AC had the airbox on the back of it too.

The 120Sc was the next generation and the air box was incorperated into the valve cover. This is where the Plenum box has been every since on the large engines...120's, 140's, 160, and now the 170. The larger valve cover area allows YS to use this area as the plenum or air box.

On the 91 it was released at the time the 120AC was on the top as far as performance goes. Its valve cover volume is a bit smaller and they were sticking the air boxes on the back.

Then the change was made on the big engines becasue of weight I think mainly and they went to under the valve cover. The 91AC evolved into the 91FZ, some minor changes but really close ot the same engine. The 91FZ was then bored out and made into the 110FZ, again very similar engine just a bigger displacement and more power. Now the 110S comes to the scene 12-13 years after the initial 91 and the same basic priniciples have not chnaged in how it works so there is no need to put it under the valve cover. The engine is already very light weight for its power and so on.

I would suspect that at some point the YS 110 may morph into a valve cover style airbox, but I don't know if there are any plans in the works to do this.

There have been lots of developments since the 120AC. These would include the 120SC, then the 140FZ, a 120FZ was produced, the 140L, and then big engines when mechanical fuel injected with the DZ or Dingo engines. The DZ's started with the 140DZ, the 160DZ , and now the 170DZ is about to be released.

YS spends lots of development time on the latest pattern engines. This is where they focus their energy and talents. The lessons learned and used on the big dog will trickle down tot he sport engines.

As for the 63 not haveing an air box its a smaller engine and again is very light for its weight...They just have not put an airbox on it yet. If they will at all.

Simple answer is its a different design and have fine tuned it over the years to work that way. There is no need to change it yet.

Troy Newman
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