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how do you stop syphoning

Old 02-04-2013, 01:59 PM
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sparky4lawndart
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Default how do you stop syphoning

hey guys... I installed my incredibly reliable and beloved YS F120 in a warbird and I'm ready to pull my hair out...

I have my YS F120 inverted in a H9 60 size P-47 and it's syphoning in a bad way... (at least, i think it's called syphoning). Apparently other motors suffer the same issues... if the tank centerline is the same as the carb the fuel will literally stream out of the exhaust port when you turn over the engine... I can't get it started at all anymore while just last week while the engine was in a Zen120 pattern plane where I could sneeze and the engine would start and idle pretty as you please.

is there a do-hickey to prevent syphoning or do i have to tear up the fuse and wing top to put the tank lower than the carb?
Old 02-04-2013, 02:10 PM
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petec
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Default RE: how do you stop syphoning

The YS fuel system is not susceptible to siphoning like a carbureted engine. If your engine is streaming fuel out of anything the regulator is more than likely stuck open.
Old 02-04-2013, 02:17 PM
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ThumbSkull
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Default RE: how do you stop syphoning

The tank is pressurized, if fuel is coming out without the engine turning over, then your check valve (diaphragm) in the regulator has crap in it or it needs a new one.
Old 02-04-2013, 03:21 PM
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mtcarey
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Default RE: how do you stop syphoning

Yes check your regulator.
Old 02-04-2013, 03:28 PM
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sparky4lawndart
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Default RE: how do you stop syphoning

how big a deal is it to back that big thing (1/3 inch wide dohickey with a flat head slot in it) next to the prop hub out the bottom of the motor... any special considerations?
Old 02-04-2013, 07:33 PM
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Jimmy Skids
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Default RE: how do you stop syphoning


ORIGINAL: sparky4lawndart

how big a deal is it to back that big thing (1/3 inch wide dohickey with a flat head slot in it) next to the prop hub out the bottom of the motor... any special considerations?
Your wording is hard to understand. The regulator assembly is what holds the flat head slotted screw at the bottom of the motor. Before backing out the screw, I would suggest removing the two Allen head bolts and take the assembly off to make sure there is no dirt, etc in the assembly. Then re-install and try the motor. Also please note that there is a right way and a wrong way to install this part. You must have the "mark" on the case pointed towards the prop.
Jim
Old 02-04-2013, 07:34 PM
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Jimmy Skids
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Default RE: how do you stop syphoning

Also, what fuel?
Old 02-05-2013, 07:34 AM
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sparky4lawndart
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Default RE: how do you stop syphoning

Jimmy... sorry... yes.. it's the regulator assembly. I found a copy of the YS FZ120 owners manual... what the exploded view doesn't show is the manner in which to clean/service the regulator. I'm using YS 20/20 fuel (very expensive btw).

I'm going to try again tomorrow morning at the flightline and see what I can make happen... I spoke to a gentlemen who explained that there are actually three setting screws for low, mid, and hi (the big needle). opposite the throttle arm is the low speed adjustment flat head screw, the regulator is the mid range adjustment, and the hi-speed needle.

I've been trying to start the motor with the hi-speed needle out 2 1/2 to 3 turns... he recommended starting it at 1 to 1 1/2 turns out and tweek from there (low and mid range screws flush with case).

What's funny is I had never touched any of those settings once on the Zen120 plane... all i ever did through 4+ gallons of fuel was fill it and go. never changed a plug. it spun a 16/8 pattern prop at about 9000RPM every time i checked. I'm worried that something more fundamental is different.
Old 02-05-2013, 03:34 PM
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Jimmy Skids
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Default RE: how do you stop syphoning

Pretty simple. Remove the two allen head screws and take the assembly off the motor. Rinse with raw fuel and replace in the same manner it came off. You can also make sure that all the ports are clear and that there isn't any build up from raw fuel. The regulater screw should be flush with the case. The low end needle should be 1 and 1/2 turns from closed and your original starting point on the high end was correct at 2.5 open. More than likely if you have fuel pouring through after prime, the regulator is "stuck" open. When you remove the assembly there is a small plunger that should move up and down. The plunger is spring loaded so that when you GENTLY push it down it will return. The up and down motion is a very small amount, but it should move and return. If it isn't, then you may have an issue with regulator functioning correctly. I have attached the FZ instructions as a starting point.

Lastly, make sure you are using an OS F plug or a YS 4 stroke plug. Also, I highly recommend the Cool Power brand of fuel. If you run the motor dry after flying, there can be months between flights and no issues when using Cool Power.

Jimmy Skids
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