Well this engine is the king of the hill when it comes to 4-strokes and seems to pack a lot of power as well..

The question I have is how hard is to tune? What about maintenance, do you constantly have to retune it or is it set it and forget it?

I have only had Saitos and OS before, they were really good... but in this application I need the power of the YS.

Look.
YS engines are the most powerful 4str. available.
But,
tuning is a thing to think about it.
My friend has many YS engines.
He builds onlly kits,not even one ARF trainer.
He says that he trust YS because they don't quit and also they pressurize the tank....=>constant fuel delivery to the carb.
So,until now i've seen three of his plains crashing hard.
A Marutaka Corsair with a YS 63 FZ-S crashed first flight.
Not a construction problem not fuel.
He uses Cool power 15% nitro.
Second was [X(] Cap 232 from Tettra.
It had many flights with it,no problem or messing with the YS 91 AC that has.
But one and a half month ago we went on the field,he took off and after the first turn the engine just quitted.
...maybe not good reflection characteristics + windy day and crashed it.
And the third was an Acrostar Tettra kit with a YS 110 FZ.
And things went exactly as with the Cap above.
I am not trying to discourage you.
Me?
I bought a YS 53 FZ used,it was in a very good condition.
Good bearings etc.
But couldn't tune it to run correct except idle.
Maybe it was an old lemon ofcourse.
So,
back again to the topic,
needles it all engines must be inspected ones in a while.
You don't tune an engine and leave it.
You check it periodically.
And when we are checking it's power?
The best.
It is the most powerful engine in it's class in comparison with all other 4strokers.
The only,
messing things i dislike in a YS are:

1) High nitro percentage=>that costs a lot.
2) Hard to tune it because it is NOT a SIMPLE engine.

I'd better go with an OS 120 FS Surpass pumped if weight is not a problem.
The YS 110 FZ weights 800gr with muffler vs the OS FS 120 Surpass/p that weighs 1000gr.
For 200gr i would go with the OS.
And i would be sure about what i bought.
Enjoy.
Kostas
Greece

I have the YS53, /63, /91, /110 & /120, mostly in pairs. It is a wonderful product, good for an extra inch of prop diameter compared to the OS/Saito type (which I also have & enjoy). They are a little trickier to tune than a standard 4-stroke, but not a lot. There is the added variable of the regulator screw, which most of the time can be left flush with the crankcase and no special trouble. The pumped, regulated, pressurized tank simplfies tank plumbing, and I prefer this kind of fuel delivery system over any other.

Four strokes all come with instructions saying you need to set the valve clearances every so often. In my experience, once a season is usually enough, but I did have a (non-YS) 4-stroke once that would not hold it settings well.

The high nitro is a disincentive for some. If you burn just a gallon or two a year, then the added cost is not so bad. If you fly hard several times a week (like us retired old farts), you can buy high nitro in bulk and it costs what sport blend costs at LHS retail. If you're in the middle, buying 3-6 gallons a season, then you may resent the added cost. The YS is not happy if you skimp on nitro or lube--gotta be 20/20 on up to 30% nitro if you like (and I do).

The YS has a wonderful supporter in Troy Newman, whose tuning posts are legendary. Look them up, and you'll know everything there is to know about tuning a YS.

HOWEVER, with specific regard to the 110: I bought a new YS110 last year, broke it in according to the book. Tuned perfectly on the ground, idled @ 2000 rpm, throttled up beautifully, fuel Magnum I, APC 15x8, everything right on the money. However, after the first ten flights it started hesitating when I would throttle up from flying idle to cruise power--as in coming down from a stall turn, for example--it would seem to gag for a moment, then catch and go. Pretty soon it would gag and die. For the next few weeks, it kept doing this, and I kept trying to tune this out. Just about every flight ended in a deadstick after a few minutes flying.

I posted for help to the YS engine forum, got a response from Dave Shadel, whose answers are usually clear and effective. No improvement. Then not too long ago I saw a post from Seanychen here on RCU describing the same problem, citing many other 110's with the same problem, blaming air leaks (all with new engines!). Seanychen's contribution was to turn the regulator all the way in, then back out three turns, problem went away. I switched to another YS110 last year (bought used, flew great), and have not yet had an opportunity to try the three-turns solution.

If you are strictly a plug and play guy, get yourself an Evo from H9 and have yourself a good time. If you are not afraid to twiddle with an engine, the YS is definitely worth learning how to tune and maintain. It helps tremendously to have a YS guru locally who can help you on occasion, but I was able to learn it myself with the help of the Troy Newman posts. Power to weight the YS is in a class by itself.

hrm... I may just go with a tried and true 2-stroke like os 120 ax looks pretty good...[&:]

The 1.10 is a awesome engine. Mine started up out of the box and emediately idled at 2000 with no adjustments. The loyal OS guys watching it just watched in tears. My 1.10 when new turned 9,300 with a APC 16-6, and after 1 gallon turned 9,800-9,900. I also tried a APC 16-8 and it turned approx 9000-9100. The engine has a idle and throttle responce that is unbeleviable. Follow the instructions and as long as your not a needle jockie, the engine will run awesome. You must think about how the adjustment is going to affect the engine before you do it. After my engine had 1 gallon thru it, I never adjusted the needles again for the next 3 gallons.

"Tried" maybe but I have not heard much on the "True" yet since its a new engine.

Majortom, THANK YOU! I am having similar problems with my YS110. I would get 10 flights, then would have trouble transitioning from idle. My solution was to change plugs (OSF's) but obviously this was getting expensive. Dave ran out of advise unfortunately, but I'm going to try the 3 turn suggestion.

I'll also agree that when YS's are running they are powerful and sweet, but one does need to tune them a lot more than an OS or Saito.

My experience with tuning YS's is that, once they're tuned, you can leave the needles alone as long as you don't change prop or fuel. Even last year's tuning is still good this year. But change the prop size, or fuel blend, or both, and you'd better get ready for a little needle time.

I'll add the fact that it's easy to tune as long as you don't 'chase' the low end adjustment.

After each tweak of the low speed screw, rev the engine a few times and let it settle down to the idle before rechecking if the mixture is correct.

-David C.

The 110 is a good strong engine, just like the other YS. I have a 63FZ, 110FX, 140DZ and 160DZ. My suggestion, feed it the proper fuel, prop it correctly, and spend some time getting it in tune. You'll be very happy with the engine. I think the #1 problem with those that have YS issues is wrong fuel, poor prop choice and settings out of wack.

As to your specific questions, it isn't exacly hard to tune, but it can take a little while, but it is worth the effort. Once set, it is pretty much forget as long as you don't change fuel and prop, as others mentioned. As for maintenance, a occasional valve clearance check and maybe a gasket and o-ring set once every 1-2 years, depending upon use.

Cheers.