New YS91 unstable idle

[marked23]

I've got a new YS91 and it either idles too fast, and starts to grab the clutch, or it idles too slow and dies. And it can do this all on the same needle setting.

And it's spitting unburnt fuel out the pipe... at idle. Quite a lot.

And the transition from idle to spin-up is unreliable. If I'm careful with it, I can spin it up. A leaner idle needle setting and it dies (fast) while spinning up. A richer idle needle setting and it sputters unhapily while it comes up to speed, and then it's ok.

The four-second pinch test seems good.

Removing the glow igniter changes the note of the engine just a bit.

I'm using OS#8 glow plug and CP30.

Is this normal for a new YS? Or do I need to play with my needles more?

-Mark

[WayneBrown]

You need to play with them more.
I've got one too, and I ended up after one tank at 1 1/3 turns on the main, and 1 on the mid. Idle is still rich, but at least it runs.. :D
The next step will be to lower the regulator pressure a bit, but it's risky if you've never done it.

[NolanManley]

Put in a Enya #3 or suffer the consiquences. None of my YS91's ever ran good on an OS#8.

Is your check valve is working ok, should be able to blow hard into it and have the valve open. Also the length of the tubing from the engine back plate to the check valve is fairly critical.

Other than that you have a blockage issue in the carb regulator system.

[Alfred]

How often do you fly per week?
Do you fly just on the weekends or also during the week?
Depending on the amount of usage I suggest to treat the engine accordingly.
If the engine is being run just on the weekends then I higly recommend to completely run it dry at the end of the last flight and keep starting it until there is no more firing being noticed.
In this case, the engine on the next flight will run fast 1st but then slow down after a short while and maybe even stop. This seems to happen because of the pump and chambers not being completely full yet (guessing). this just happens on the 1st start and is then good for the rest of the flights.
If you don't run it completely dry, get used to replacing bearings every 6 months or less.

If you fly more often as every few days, ignore the above suggestions.

I have three YS engines....YS61ST-2,YS80,YS91
Two of them prefer Enya#3, one prefers the OS#8.

[marked23]

It's interesting that you suggest an Enya #3. Back when I was messing around with trying other plugs, I was trying some cooler plugs in my OS91. The way my YS91 acts on an OS#8 is very similar to how my OS91 acted on an OSA5 plug.

So the Enya #3 will be the next thing I try.

I do run the engine completely dry after a day of flying.

I tried blowing gently into the check valve and air did not move either way. So rather than force it, I just assembled it and that part appears to work. I'm getting pressure to the tank that stays there long after the flight. I have 10cm of tube connecting the engine to the check valve.

-Mark

[NolanManley]

HHhmmmm Mark, Have you check the head bolts. I have had them loosen up on mine before.

If not that it might be an air leak on the carb system. This one is a pain to find.

BTW..You won't hurt the check valve with just mouth pressure. :shock: But that's not the problem since you have tank pressure.


What really is bothersome is that you said it is a NEW engine. It may just have a factory defect.

If you can't see anything wrong and have tried all the suggestions it may be prudent to sent it in under warrenty or return it for another. :(

Good luck :)

[tjjmon]

I have the same problem with mine. I also run 30% CP and an OS 8 plug. Tried an Enya but in my case it made it worse. Cleaned carb, new check valve, new diaphram, and checked head bolts. I've learned to live with it but from what I've heard about YS engines (set and forget) it is disappointing.

[NolanManley]

I flew my Stratus with YS91 today after is been parked since last Oct. YES that's LAST October!
I changed all the fuel line on the heli and ran er up. It flew pretty good but after the first landing and letting it idle for a min, the engine quit on spoolup. Fiddled with the needles a bit with no luck. One of my flying buds said have you changed the plug? I said hell no, it's only two years old. :shock: Guess what .... Yep, that did the trick. (another Enya #3) Runs like a champ and plenty of power.

After experiancing how well this engine (and others I have used) did I can only assume your engine might have a defect. It seems you've done the right stuff to solve most any problem with the YS.
Don't live with it get it exchanged.

[Endo]

Mine has the same problem with #8. Only about 3 gallons thru it so far. tons of tank pressure. Let us know what the plug change does.

[marked23]

The Enya #3 helped. It was noticably better. So I'll keep messing with it for now. I'm running the idle a little fast because I just don't trust it to run slow. Because of that, when I hit hold to do an auto, the engine never seems to settle down.

But, yeah, it's better with the Enya #3.

-Mark

[DebianDog]

Keep messing with that low end screw and once it starts and warms up dial it back to where it is running good.

Greg Alderman showed me a neat trick using a Duralite Glow and Test.
http://www.duralitebatteries.com/images/lg-pdlt.jpg

He showed me that my engine was flooded by how many amps I was pushing. Sure enough we cut the fuel and she started. Now that the YS has a few more tanks though it it seems to start better too. I may try the Enya as well. Not quite ready to blow $135 for a glow igniter though.

[Gary O]

The low speed on a YS engine is really critical, and very sensitive too. Just small adjustments make a significant difference in tuning. What I do as kind of a habit when I rebuild one or put in a new one is start with the idle screw about flush with the carb body and go from there. If you get too lean with the low, it will never run right.

[marked23]

I'm not sure if this had anything to do with my problems, but I just had my clunk line disolve during a flight. It was the stock MA clunk line that I have been using with 30% and Muffler pressure (until recently) for 18 months. I pulled out that line and I could crush the tube and it would stay crushed. I could ball-up the rubber and it would stay in a ball... like dough.

I'm still using the Enya #3 and the engine reliability is still improving. I figure the new clunk line is helping too.

-Mark

[DebianDog]

I tell you what I was out flying yesterday and now that I am getting more flights on my YS it is running better and better and starting easier! :smokin:

[Gary O]

Mark, that's too long to let any fuel line stay in the tank, especially running muffler pressure. The black "Hayes" clunk line will last longer but any line needs to be replaced after several gallons of fuel. I change all my fuel line out after 5-7 gallons.

[DavidH]

When using muffler pressure. I would change the clunk line in the tank at least every couple of months or about 4 gallons of fuel. Which ever came first. Exhaust gases in the tank will destroy the clunk line in the tank.

With the crankcase pressurized fuel system. I don't worry about the clunk line in the tank since it is a closed loop system. I check it about every six months or so.

David