I sent in my YS .63 for service a couple weeks ago. I sent it in because it ran terribly. It made a terrible sound and usually died when you increased the throttle, never held a reliable top end, no reliable idle, and it was pretty hard to start.

I got the engine back today. A new piston, new ring, and a new plunger was put in. The bill was $70 (enough for a new .40). I was expecting to have the best engine around (just like I did when I bought it). So far I've got $320 invested in this engine.

I put it all back together and mounted it back on my model. I put the 13x6 on, YS 20/20 fuel, an O.S. F plug, and opened the main needle 2.5 turns to starts.

I took it out and fired it up...Nothing has changed! NOT reliable, a TERRIBLE sound is heard with a quick increase in throttle and everything else is just like it was. Obviously, I am not too happy. What's going on? What happened? What am I doing wrong?

I've never seen one run at 2.5 turns open on the main needle. Normally 1.5 to 1.75 is about right. At 2.5 turns I am surprised that it will run at all without flooding.
My guess is that the whole problem is adjustment. Try it and let me know.

Thank You,
Dave

I did lean things out, up to only 1.5 turns out. It does not change things...

If they shouldn't be run at 2.5 turns out, maybe it shouldn't say to do that in the manuel that came with it.

2.5 turns will only be a beginning when the engine is new so that it will be very rich. Like I said. the engine should run nicely at 1.5 or so turns open.
I still suspect the problem is in your adjustments. If you would like to send it back in for us to confirm that please do so.

Thank You,
Dave

Hey kane77, sounds like your fuel is stale! my 2 ys DEMANDS fresh fuel, and fresh plugs. Don't give up on it untill you try it! If it dont work, I got a Saito .72 to trade ya!(wink, wink!)

Sorry it took me so long to get back to this.

I took my tank apart and tested it and found a link by the screw that hold the stopper together. I put in a new stopped and a new screw and still had the same leak (when under pressure). I put a bunch of sealer and glue and whatever I had to do the trick over the whole stopper assembly and screw. No leak! I felt like I genius...

I fueled it up with a brand new gallon of YS 20/20 and also a fresh O.S. "F" plug. It fired right up.

Ran PERFECTLY!

Sorry green river rc, but you're gonna have to keep that Saito!

I forgot to mention, always those o.s. f plugs. and how come nobody wants to trade there Y.S. for my Saito? L.O.L.!

I always use those O.S. "F" plugs...I use O.S. plugs for everything, even though I don't like their engines...

I finally got to fly it today and it was perfect..Got 2 great flights, but then I had a problem. I couldn't get it started! I think my tank is leaking again!!!!!

Tank is not leaking...It just won't start!

I am haveing exact same problem. will only run at 2.5 turns out on High end.

What should the low end be set to. I think I have tried everything.

I got mine running perfectly!

Low end needle is 1.5 turns out from closed.

High end is the same.

Regulator is flush with it's housing.