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YS 120 wont run

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Old 12-30-2009, 11:11 AM
  #1  
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Default YS 120 wont run

Hi....need help...bought a second hand YS f 120 ..one of the first models...got the plumbing as per the drawings...it revs ok at low speed, but as i increase speed the fuel goes back to the tank as the regulator does not seem to send fuel to the carb, as a result the engine just dies.....but one thing i noticed is that the crankcase seemed to be full of fuel to the piont of flooding.... i have to release all the fuel in the crankcase by tuning the engine over with the plug removed to get rid of the fuel....help...ps i do have the non return valve in as per the drawing
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Old 12-30-2009, 11:29 AM
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Default RE: YS 120 wont run

You could check your fuel diaphram and/or replace it. YS Parts America, http://www.yspartsandservice.com/index.php , is a source for the part. Talk to Richard.
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Old 01-01-2010, 03:53 PM
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Default RE: YS 120 wont run

sorry mis read the post
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Old 01-11-2010, 09:19 PM
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Default RE: YS 120 wont run

Is your fuel tank getting pressurized?
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Old 01-14-2010, 10:12 PM
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Default RE: YS 120 wont run

If the regulator is installed backwards they can do that. Easy mistake to make as it fits fine rotated 180 degrees out. Might be your problem. There should be an index boss on the regulator housing, i.e., a small metal tab. I can't remember which way it is supposed to point, but if you look close it is shown in one of the views of the engine in the instructions. If it is wrong, I can gaurentee that is part of your problem.
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Old 01-15-2010, 11:02 AM
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Default RE: YS 120 wont run

Did you install the one way valve in the return line? Dennis
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Old 01-19-2010, 10:37 PM
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Default RE: YS 120 wont run

Wishing you better luck than I had. I bought an older model NIB, NC model I think. I fought with that sucker for two weeks and threw the towel in. It sits in the closet (almost NIB). I don't have the heart to sell the problem to someone else and I've tried to give it away to a couple of friends... who would take it only if I threw in a bottle of aspirin.
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Old 01-19-2010, 11:42 PM
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I'll take it and you can keep the aspirin .
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Old 01-24-2010, 04:36 PM
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Default RE: YS 120 wont run

i would be more than happy to take it as well.. a lot of people don't like ys because they are a bit different, and if you don't understand the fine details of how they run, you will have more headaches than you think they are worth. I have a 91, and a 120, love them both..
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