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Old Jun 17, 2007, 03:14 PM
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Alpharetta, GA
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Ys 120-sf

This is the original YS-120 (it says F-120 on the motor, but they all do). I bought this "new in the box" last summer and have probably ran about 2 gallons through it. I'm moving to larger planes and gas engines, so I'm selling all of my glow stuff.

This is a very strong engine, never crashed. It comes with the straight pipe exhaust, check valve and lock nut for the prop shaft. If you're looking for something to outperform any Saito 125 on the planet and sound like a Harley while doing it... this is your motor!

Price - $250.00 plus actual shipping charges

THIS PLANE WILL SELL TONIGHT ON E-BAY.. NO MINIMUM. If you're interested.. you could get a real deal.....

http://cgi.ebay.com/ws/eBayISAPI.dll...m=270136271524
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Old Jun 21, 2007, 10:08 AM
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Joined Dec 2005
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What is the purpose for the check valve? Is this unique to the YS?
I know what a check valve does, I just do not know why it is needed on this engine.
Thanks
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Old Jun 21, 2007, 10:17 AM
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The YS engines use a pressurized fuel tank system (part of their "supercharging" system). The check valve sends pressurized fuel from the engine into the tank, and does not allow fuel to back-flow throught that line from the tank back to the engine.

On the other tank like (there are only 2 for YS), you have the inflow line from the tank into the fuel pump. The needle valve meters fuel from the fuel pump into the carb... so the fuel system is always pressurized at about 4 pounds per sq inch. The result is no hesitation through the mid-range... absolutely smooth power throughout the bandwidth... and about a 20% increase in horsepower.
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