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Well, Ive turned every screw I can turn every which way but loose on my new YS 110. I don't know how to get it back to factory settings so I can star all over. I'm having trouble getting a sustainable idle inverted on my old Gold Edition P-40. I was so impressed by Rishard L's that I had to have one. This engine discharges quiet a bit of raw fuel on throttle up and I don't know whether the low end is too rich or the regulator is too rich. The frustration is causing me to want to put the OS 91 back in. I'm using BYRON 15/18 fuel with an OS F plug. It also drips fuel from the carb in between runs. Ive run it about 15 minuted total on full throttle at about 8500 rpms with a 14-7 3-blade prop.
Can someone come to the rescue?

Carl
409-658-2678
Beaumont, Texas 77705

I have a YS91AC and the only way it will run consistently is on YS 20/20 fuel. Mine also leaks a bit out of the carb when running. Mine also is a bit hard on the OS F plugs. They last for a few months where they will last two years in a Saito. I want to try a colder plug and see if it is less prone to detonation.

Try this

Set the pressure regulator (big brass slotted screw) to be flush in its housing.

Open the high speed needle 2 turns from full closed.

Open the low speed needle 1.5 turns. Remember it works reverse of the high speed needle.

Start the engine and let it run for about 2 minutes at approx 1/3 power.

Then try a full power run. Adjust the high speed needle to get best RPM then richen by about 1/8 of a turn.

Then pull power back to a slow idle and see how it behaves. If it idles up on RPM and dies the low end is lean, the low speed needle should be screwed "IN" to richen the bottom end. Make these adjustments about a 1/4 turn at a time.

When the idle is reliable then try to see how it transitions. If the transition is not smooth and sags then you need to back the regulator out
a little at a time until it transition smooths out. It the transition uneven and blasting exhaust then you need to adjust the regulator IN just a bit at a time.

Remember to make all adjustments in small increments and wait for the response.
Also adjustments to the regulator may require tweaking the high and low end needles a bit.

I have had glow plugs in my YS engines last full seasons of sport flying (OS type F).
And I only use YS 20/20 fuel.
Good Luck.

If you decide to give up on that 1.10 let me know....Lets make a deal. 8)

Factory settings are 1.5 turns out for both the low end and the high end with the regulator screw flushed with the engine casing. These settings are stated in the instruction manual. The engine should run fine at these settings. Tuning a YS requires some brain power, so you got to know what you are doing and can't blindly turn the needles. BTW, I've been using the same F plug in my YS 110 for close to three years now. In fact, my other three 110's are still on their original plugs.

Thanks to all who responded to my question. My only remaining question is will the low end needle reach a stopping point before it falls out of the engine, indicating that it is completly closed? Otherwise how will I know that it is closed so that it can be set at 1 1/2 turns?
By the way , I don't give up easy. I struggled for six years learning to fly this P-40 repairing and rebuilding it three times. It was all well worth it for all I have learned during this time period.
Thanks again Guys.

Falling out = completely opened, not closed.

Turn the low end needle all the way in clockwise until it stops, then turn it back out 1.5 turns. You should not need to open it more than 2 turns. If you are more than 2 turns out, then you are way too lean on the low end.

By the way, under no circumstances should the low end needle be opened so much that it falls out.

Take a look here.

http://www.geistware.com/rcmodeling/...ys_engines.htm

Read the carb adjusting section: Adjusting YS 4 Stroke Engines - by Rick Mattie

Worked for me and now I love my 1.10.

You can ask the expert (Dave Shadel) by going to

Radios, Engines, Batteries, Clubhouse and more >> Engines, Gas Engines & Fuel Talk >> Engine Manufacturers Direct Support Forum >> YS Engines Support

Yeah, but most of the time, his answer tends to be "Send It In", even for a problem with trivial solution. That's how they stay in business

Richard I unmounted the engine so I could see everything, got the regulator flush, and low end to 1 1/2 out. Tommorrow I'l pick up some 20/20 and try it again. If you don't mind what type of manifold are you using to get the exaust routed where you have it on the pictures I saw? I could'nt see the exaust side of the engine.
Thanks for your expert advise.
Carl.

Thanks. I his information printed.

Texan2,

Sounds familiar.

First off, I am not trying to blast YS or anyone, just trying to help YOU get a running motor. See what I did, because it worked.

Don't beat yourself up tuning like a madman for days. Its likely got nothing to do with it. The motor will actually run very good with the base settings you were given already. If not, it has issues. Ive been down this road and eventually came to a good ending.

Mine was purchased when they first came out (2002?). Ran enough to fly but too many deadsticks, chronic rich midrange, and dicey idle. No adjustment would cure it. A cold 2-stroke plug was all I found that would let me lean out the main needle enough to fly it at midrange. The motor was position sensitive as well.

Finally it went to Y.S. service out of warranty (stupid me). They replaced the regulator, blessed it, and it came back running exactly the same, except I was out 65 bucks. Not sure what happened at YS service that time, but I was not sending it back again. It was either fix it or straight to Ebay. If yours is under warranty... SEND IT IN, you have nothing to loose.

Since I am an old carb guy from the 60s/70s and know my way around a metering block, i took it upon myself to learn this motors fuel system from scratch. None of the guru descriptions I have seen to date have it described exactly right, but their methods do work well enough. The bottom line is there are so many variables interacting in the fuel delivery it is difficult to get your mind wraped around it all. Just make sure you have replaced the regulator diaphram with new and the reg is mounted / oriented correctly. Also check the valve clearances. After that, well, read on....

Here's what I did:

1) My engine would suddenly die after getting heated up. I found black stains on the front of the cylinder crankcase seam after a hot flight. Look for that on yours. If it's not there, don't worry about it. The factory tolerances (on my particular vintage) allow for almost no o-ring compression. I replaced the leaky cylinder o-ring with a slightly oversized one after much experimentation with various o-rings. That cured the sudden flame outs at throttle and the stains are gone.

2) The totally wet backside of the engine always bothered me, so I cut my own thicker gaskets from NAPA material for the backplate and air box. Gone are those newspaper thickness gaskets. You must do both the carb and air box for them to still line up. Cant change the backplate gasket though. No big change, but the backside is much cleaner /dryer now and it is just one more possibility off the list. Make your own judgements here.

3) Learn how to mount the airbox so the carb to airbox o-ring is really tight as it witnesses substantial pressure. Simply mounting the airbox and tightening just doesn't make any sense when you look at the direction of the o-ring interface. Instead, loosen the four cylinder screws so the cylinder lifts a bit. This brings the airbox vertically up off of the carb. Now loosen the airbox screws, and retighten them while keeping the airbox pushed downward on the cylinder the whole time. This will favor the air box closer to the carb just from screw hole clearances. Now tighten the cylinder down and you will draw down the attached airbox to compress the o-ring onto the carb straight down as it is meant to be. This is just another belt/suspender proceedure that cant hurt. Again, this helped to dry out the backside of my engine.

4) Assuming all is well with plumbing, air leaks, fuel, ect. We move to the nasty regulator. There has been some mystery surrounding this marvel of pandora. You never get a straight answer from YS as to why they need changed or changed to a different style. Here is my theory, and it has proven itself to me.

The reg is a fuel valve operated via pressure pulse. The plunger vibrates up and down during run, at the rate of the positive crankcase pulse or piston stroke. Pretty darn fast. This forms an RPM relative metering of the pressurized fuel to the carb. The carb has it's own metering slot on the throttle barrel that changes with throttle position. Those two items (RPM and throttle position) make up a major portion of the engine load demand sensing needed for any fuel delivery system (somewhat simplified). You alter the amount of RPM based metering by changing the spring tension on the plunger. This changes the dwell or "hang time" of the unseated plunger and little rubber stopper valve on the end of it. The main fuel mixture needle forms the high limit of fuel delivery at full speed, but only slightly effects lower flows. When the engine goes really fast, the plunger is just hanging open most of the time with fuel limited only by the main needle and delivery notch in the throttle barrel.

The snafu comes in when you consider this regulator plunger is submerged in fluid - fuel. During operation, this nailhead shaped plunger goes into the regulator body and seats flat against the bottom of the housing. If you have the regulator in your hand and push it in, sometimes it will stick on the oil residue for a moment then release. Hmmm. Have you ever tried to pick up a frisbee on the bottom of the pool? Cohesion it's called. Just a millisecond of this behavior while oscillating will change the metering toward the rich side. Some regulators have a brass plunger of about 1/4" diameter. Others have one about 1/8" diameter. Guess why? They behave differently and the smaller one would have to stick less.

After I witnessed how this thing sticks, it took me about 30 seconds to realize the cure. (Too bad it took me 2 years to get to this point.) On the aluminum regulator body, where the plunger contacts the flat area around the stem hole, I lightly punched an awl into the aluminum at four places around the circle. This raised four little bumps under the plunger. These "standoffs" keep the plunger from seating totally flat and bingo, no cohesion, and it would stick no more.

Finally, and only after this re-work of the regulator, the engine magically started and ran almost perfect with factory settings on the regulator, idle air needle, and 1- 1/2 turn on the main. Only a very slight tweak was needed to really tune in the idle and regulator transition.

Now a year later and it can still idle through an entire tank of fuel unattended. WOW. To say the least, I am drop dead pleased with the engine now. It does 13lbs of thrust on my 10 lb Edge. Now that's smiles

Central Hobbies used to sell a flex pipe for the YS 91/110. I don't know if they still carry it.