Sent my 63FZ in to YS service last month because it would'nt hold pressure & was leaking fuel. cleaned the regulator & tried adjusting with no improvement. Sent it in to YS service & they said they replaced some pump parts & did a piston upgrade. Got my engine back with the old regulator parts they replaced but my engine is no different than before. Will not hold pressure, I have run this engine before in a couple of my other planes so it's not like I don't know how to setup the plumbing on this engine. I thought YS sevice ran these engines before shipping them back, I have'nt touched the regulator figuring that if they ran it before sending it back it should run for me. As it is now the fuel leaks through the carburator when cranking it over. If I crank it over long enough to build some pressure it leaks fuel all over the place, then I can turn the prop slowly by hand & hear the pressure escaping through the carb. When I release the pressure from the tank I get very little or no hissing at all.[]

What kind of tank are you using? Have you tried running it? You didn't mention if you had or not.

My experience is fuel leaking out of the carburator is symptomatic of a rich setting of the regulator. You may wish to turn the regulator screw in 1/4 clockwise increments until problem is solved. Troy Newman maintains an excellent website for trouble shooting YS engines; URL is: http://www.patternflyer.com/troy/?page_id=13

Best wishes for success,
Ken

Have this engine mounted in a 40 size U-CAN-DO using the stock fuel tank. When I first built this plane the engine ran great for about 10 flights before acting up. Before sending in I tried running it but could'nt get it to fire, tried adjusting the regulator both in & out with no difference. Have not tried running it since getting it back repaired since it's acting the same as before. I'll try readjusting the regulator sometime this week turning it in(lean) & hope for the best.

Tried turning the regulator adjustment screw in 1/2 turn & turned it over with an electric starter for 10 - 15 seconds & still not holding pressure. Doing this with an empty tank as I don't want fuel all over my work table. Turned it in another 1/2 turn with the same results. Turned it in 2 turns & now shows signs of improvement. Can now get a good hissing sound when releasing the tank pressure. At this setting it's 3 - 4 turns in from flush with the regulator housing. Will try it with the tank fueled up tomorrow after work & hope it's not leaking fuel through the carb, If this goes well I'll have to wait till weekend to start her up & adjust the regulator.

You may wish to ensure throttle is open when testing to determine whether tank is being pressurized. Troy Newman points out YS FZ 63s pressurizes tank only when turning above 2000 rpm; at 2000 rpm the engine simply draws fuel into the carburator.

Best wishes for success,
Ken

Have throttle open anywhere from half to full open while turning it over.

YS does run the engines before sending them out which makes me question the fuel system in the plane. If it is leaking fuel out of the carb your regulator may have gotten some junk in it. Maybe your fuel filter isn't quite doing it's job. The other thought might be a little hole in one of the fuel lines in the vicinity of the carb that looks like fuel is leaking from the carb.

When I got the engine back from YS I installed it in my plane & tried to pressurize the tank without any fuel, leaving the regulator adjusted just as it came from YS. I think this would eliminate the question of bad/dirty fuel. As per my earlier post I adjusted the regulator about 3 turns in from flush & was holding pressure. Let it sit all night then realesed the pressure, pressurized the tank again & off to work I went. After work it was still pressurized so this would eliminate a leak in any of the fuel lines. As the regulator is adjusted now if I turn it in another 3/4 turn it bottoms out. Will try running it this weekend & further adjust the regulator.

Did YS replace the regulator spring?

The only parts I got back were plunger (brass ) & the silicone piece that fits on the end of this plunger & under the spring. I did not recieve a spring back indicating replacement. Seems as if the spring compressed & now has to be turned further in.

Got around to test running the engine today. Started right up with the regulator adjusted about 3 turns in past flush, idle is pretty good at about 2300 rpm, at full throttle getting about 9800 rpm with an APC 14x4 but will only run for about 10 - 15 seconds before she dies. Kept turning the regulator 1/2 turn out a few times with the same results. When adjusted near the flush setting it was dripping fuel & I could hear the pressure escaping through the carb. Think I should replace the regulator spring & try again.

It should run well with the regulator just barely turned in from being flush with the top of the regulator housing. If it is leaking past the regulator, you've got some debris in the regulator. Clean it out and make sure it is not leaking anymore.