I have a YS 140L, that has been quite very reliable over the years. However, I have had a 2 year "Holiday" from pattern flying.
The urge returned, so I dusted off the plane, cycled the nicads, fueled her up and off I went.
All seemed well, initally. Engine, once it was primed up, started and ran, just like I remembered it.
Idles well, pulls well.

But after the second flight, it would keep quitting when you throttled up when doing a manouvre. I would try and simulate it on the ground, but it wouldn't quit. I can leave it sit on the ground for ages idling. I can fly at high throttle, and it won't quit. But as soon as I throttle up, say at the bottom of a loop, it quits.
I have checked all the fuel lines, it has good pressure in the fuel tank when I check after the enforced landing.


Apart from the engine quitting, it was a real thrill to see a pattern plane sit in the groove, see those straight lines, SMELL the nitro and see the beautiful smoke trail coming from the plane on a clear blue sky. I have to say, I love my YS over an electric, but that's another story.

If somebody could offer some help, I would appreaciate it.

Bruce

Bruce,

After sitting that long I think the first thing I would do is replace the little diaphram for the regulator. They need it every now and then anyways so it can't hurt

I had an problem like that with my 1.20FZ last year. Drove me nuts. I changed the check valve, diaphram, and even dumped out my fuel and opened a new jug. At the suggestion of friend I took the carb apart and found a piece of grass on the cylinder pipe side of the butterfly an some gunk in the idle needle. Runs fine now, but like you I couldn't duplicate the problem on the ground, only in the air after throttle up after a downline.

Years ago I had the EXACT same symptoms; It was driving me nuts. Tony Frakowiak(spelling?) suggested the solution.
Check the rocker cover gasket for leaks. I replaced the gasket, problem solved..

Old Dawg,
Long Live Team Vegas

It could be a number of problem. Sitting that long I would rebuild the pump, and replace the gasket on the valve cover. It's just a common problem for Y.S. They don't like sitting around, they were built to run!

Hope this helps,

Rick

Thanks guys for all your responses, I am working it now, and will post an update.
I do recall, some years ago, it kept stopping mid flight at a comp, and one of the more experienced guys there told me to check the rocker gasket. In that case, the screws were loose. But in my case now, they were tight. However, the gasket looks a little seedy.
So I go through th ewhole fuel system, replace all the gaskets, and make sure it's squeaky clean, and post my results.


BTW, what headers,mufflers(pipes) are you guys using on your pattern planes, with the YS?

Thanks, Bruce

A problem with an L.... No way, lol..
I had your same problem with my L when I first bought it. Sent it back and they replaced the piston, liner, regulator diapragm, and gaskets. I got it back, flew great for 20 flights, then started having more problems. I had replaced all I could replace. Even sent it back in. And only ever got about 10 more flights on it.
Anyway, back to your problem I think it's probably an air leak. Remember even though your plane may be horizontal in the air, or sitting on the ground, there is alot of air flow over your engine while in the air. Therefore creating problems such as the one you say you have.
Easiest part to replace also. The valve cover gasket...
Before putting the valve cover back on. I make sure it is 100% flat also. If not I put a piece of sand paper (fine) on a super flat surface, then put the valve cover down on it and move it back and forth slowly.

Also, as it did sit for along time I would definitely replace the diapragm, plunger, and gasket..
Also adjust valves.

I used the dz header with two copper gaskets mounted to the engine. And I can't remember what pipe.

Well,
I changed all the gaskets, the regulator diaphram.

Now it runs like clockwork. I suspect, the carby gaskets were all ok, the rocker cover gasket was a bit lumpy.
I gave the rocker cover a light lap with some 600 grit paper too.

It's great to hear thos YS's, I love the low pitch "snarl" they make as they run just above idle.

Thanks everybody for your help.

BT