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YS 140 SPORT RUNS TERRIBLE

Old 05-05-2008, 11:51 PM
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cpe190
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Default YS 140 SPORT RUNS TERRIBLE

Hi, I have a new ys 140 sport that will idle ok but runs very unstable at mid and especially high speed. Almost seems lean but when i try to richen it up nothing really happens just runs worse. I have the regulator set flush and have tried adjusting it but just seems to make the problem worse. I have the check valve installed and am getting pressure when remove the line from the check valve. Also i am running an APC 16 x 10 prop? Please help
Old 05-06-2008, 12:39 AM
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Default RE: YS 140 SPORT RUNS TERRIBLE

Try a new OS Type F plug. If that doesn't work, try running the engine at 4000 RPM and adjust the regulator. If that doesn't work you probably have some dirt in the regulator or carb. My two cents
Old 05-06-2008, 01:56 AM
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Troy Newman
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Default RE: YS 140 SPORT RUNS TERRIBLE

here is a good link to some details.

This was written for a 63 but the same applies to the 140 Sport. The magic numbers for the 140's is between 8400 and 8800. The 16-10 is a good prop choice to be in this range.

One thing you didn't mention was your fuel of choice. You need to be running between 15-30% nitro with 20% oil content. I recommend all synthetic oil. You should not use any type of 4 stroke fuel. They are usually low nitro and don't have enough oil content.

I will also go so far as to say you should not try to run 15% nitro....its just tougher to get the settings.

The fuel I choose and recommend to others is Cool Power 30% Performance Heli. The higher nitro fuels make the engines run cooler as the mixture setting need to be richer for the higher nitro. This means you are pushing more volume of fuel through the engine and hence more oil...this means more cooling.

Also the higher nitro makes the Sweet spot in the mixture wider...makes it easier to get the settings correct.

The glow plug needs to be a OS #F or a YS plug. They are the same plug.

What you are describing is almost like bad fuel...but there really is not enough information in your post to tell what is going on.

I hope this helps you.

Troy Newman
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Old 05-06-2008, 10:59 AM
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cpe190
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Default RE: YS 140 SPORT RUNS TERRIBLE

Thanks for the input. I am running Red Max 20/20 and the fuel is kept i an cool place. also never has been opend until a couple of days ago i opend a brand new bottle. Basically what is happening is this: The engine fires up perfectly and seems to run ok for about 5-7 seconds at full speed, then the rpms drop dramatically as if it was too lean, i try to richen it up quite a bit but does not change the way it is running too much. I do have an os type F plug in it as well. Also i did bench run around 5 tanks of fuel through this before i put it in my airplane. I dont remember it acting this way when i bench ran it but i did have it fairly rich. I am getting pressure to the tank because when it take the check valve off after the engine has been run, it releases a fair amount of pressure.
Any an all help would be appreciated. Thanks
Old 05-06-2008, 11:15 AM
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cpe190
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Default RE: YS 140 SPORT RUNS TERRIBLE

One more comment about my YS 140 is the fact that i do not have the muffler on it? I have the straight pipe that central hobbies sells. Can this make the engine run funny?
Old 05-06-2008, 11:33 AM
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Troy Newman
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Default RE: YS 140 SPORT RUNS TERRIBLE

No it will make the engine run richer without a muffler...but thats it.

I still think is sounds like bad fuel. Try a fresh gallon, or another gallon from another batch.

Pressure to the tank is good, but if the fuel has some junk in it...that will clog things up...One more check...

Check your fuel filter...if you have some crap in the fuel....you may have gotten lucky and its in the fuel filter and not the regulator parts....

What you are describing....sounds like bad fuel or a really scratched up piston, liner and ring. Since I assume this is a fairly new engine I doubt things are really scratched up inside....Does the engine turn over smoothly?


I think the next thing is to buy a different gallon of fuel and try it. A "fresh gallon" that was made at a different time than the one you are using. We are just trying to eliminate possibilities here.....Because it really is acting like bad fuel.

Troy Newman
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Old 05-06-2008, 11:41 AM
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cpe190
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Default RE: YS 140 SPORT RUNS TERRIBLE

The engine turns perfect. Very smooth good compression. I will try different fuel> however the odd thing is that i tried running it last fall on red max 20/20 and it still did the same thing. Then it was also a brand new gallon of fuel. Maybe i just have a bad batch of fuel? Are YS Engines more sensetive to bad fuel than other engines? I will also check the fuel filters as well. Thaks
Old 05-06-2008, 12:16 PM
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Troy Newman
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Default RE: YS 140 SPORT RUNS TERRIBLE

No they are not more sensative than other engines...However if the fuel is dirty with dirt and debris in it....they can be extremely troublesome. The regulator has many small passages and places for dirt to hide.


One other thing. Remove the HS needle and turn the engine over with a starter....the fuel flow should flush the HS needle housing this can be an area where a piece of debris can lurk...


Also double check you plumbing and lines....

And a thought just hit me..Are you using any type of fuel filler valve? These are a bad idea and will leak air....making the enigne go lean.


Troy Newman
Team YS
Old 05-06-2008, 12:30 PM
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Default RE: YS 140 SPORT RUNS TERRIBLE

I don't mean to be a bug, but did you try a brand new plug? The reason I ask is because I had a plug that would idle fine but when I went full throttle, it would barely run. I thought I had blown the engine. I wouldn't believe it was the plug because it was fairly new and it idled fine. I changed the plug and it ran like new.

If it is not the plug, then it sounds like the regulator is not working properly. If it is not allowing enough fuel to pass then you won't have enough fuel at full throttle, even if you open the needle valve a lot. The adjustment screw being flush is just a starting point. I would go through the instructions in the link that Troy gave you and see if you can get the regulator set right.

The other thing I would do is change all of the fuel lines, especially the ones on the engine. You might just be sucking air somewhere.

Blessings, Terry
Old 05-06-2008, 02:58 PM
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cpe190
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Default RE: YS 140 SPORT RUNS TERRIBLE

Yep i did change the glo plug and it did not make a difference. I dont have a fuel filler valve at all. Just the 2 lines exactly how YS sais to set up everthing. I beleive fuel can be an issue but i run rc boats as well and run this very fuel in all of them and they run just fine. I beleive it can still be fuel related but i will go ahead and flush the fuel through the HS needle and maybe change the fuel lines as well maybe check the regulator as well. I will let you know how this all works. Also if you have any other pointers it would be greatly appreciated.
Old 05-06-2008, 10:48 PM
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Default RE: YS 140 SPORT RUNS TERRIBLE

You've got a fuel problem. Can you hook up a remote fuel tank so you can eliminate that portion of the problem? If that doesn't fix it the next easiest thing is to turn the regulator out one turn and see if it will stay on track at full throttle. That may be too much but at least you will know if it is set too lean. If at this point you have changed out all the fuel lines and none of this has worked it's most likely that there is dirt somewhere in the system.

Blessings, Terry
Old 05-07-2008, 12:38 PM
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cpe190
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Default RE: YS 140 SPORT RUNS TERRIBLE

Good idea. I will hook up a different tank and see what happens. Thanks for the help.
Old 05-13-2008, 09:29 AM
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Default RE: YS 140 SPORT RUNS TERRIBLE

I had a very similar issue on a well run 140 sport.

It was running perfectly. I stored it (with the plane) for about 6 months. Then when it was time to fly that plane again - no go.

I took apart the regulator and found some crud in there - not just the diaphragm, but the plunger area as well so I had to remove the regulator screw as well to flush the complete regulator assembly with some fuel. Also replaced the regulator gasket as it had just about perished.

Works beautifully once again.

Funny thing is that the crud was reddish in colour. Hmm... not sure if the red cool power oil had anything to do with that (I use a 50/50 blue/red CP oil mix - result = purple). Never saw that before on pure blue CP oil based fuel. But one must not infer causality from one observation as any such deductions shall be deemed spurious at best.


Your RPMs might vary

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