Hye Troy I just bought a YS 110FZ from a guy, I put it on a GP geebee,, and started it for the first time today, I have a check valve, filter all the stuff is plumbed correct,, well I can start it up and it idles great and the transistion is fine,till about 3/4 throttle, as the rpms jump up past(ballpark figure) 7-8 thousand, all of a sudden I can see the fuel go out of the intake line going from the front of the engine the the clunk line on the tank,, , and the motor sags and I can let off the throttle back to below say half throttle and the fuel will suddenly shoot back in to the intake line,,, but like I said I can transistion good but when it shoots up to high rpm it acts like it sucks the intake line dry,,, (and it almost looks like it is sucking the fuel back in the tank ,very quickly),, but then I can drop the throttle back down to 3/4 throttle or below, and it fuel returns back in the line,, thanks for any info troy or anyone,, thanks,

Is the tank under pressure when you shut it down?

My guess is no.

If the tank was holding pressure then there is no way for the fuel to go toward the tank in that line.

Your plumbing is not correct or the tank is not holding pressure (has a leak).


From the symptom I would say right off hand your check valve is not installed correctly...the proper direction is to allow air from engine to the tank, and block the air from coming out of the tank.

Next thing is are you using a YS check valve. There are other varieties on the market that use a small ball bearing and a little spring. These take more pressure to close off. So when the tank is not up to pressue it will take longer to get up to pressure.

Next is to fill the tank with fuel, then plug up the check valve side and pump more fuel into the tank. This will build pressure in the tank. See if its leaking? It could be leaking past the check valve even though the check valve is installed with the proper direction. Check this. If the tank system will not hold pressure then it will not work.

The engine does NOT suck any fuel above 2000-2500rpm. It is force fed fuel above 2000-2500rpm by the pressure in the tank. The way it works is the tank is under about 6-8psi. The carb gives a little suck on the regulator and the plunger opens allowing fuel to flow past it as its under pressure. When the pressur ein the line gets to equal the pressure in the tank the fuel stops flowing and the spring will close the plunger. The only line that has any suction at all is the line from the Regulator to the Carb. This only happens when it is at the right spot in the rotation cycle and it is just a lower pressure than the 8psi in the tank. I doubt it is ever negative pressure...The enigne never really sucks fuel at all.

Now if the check valve is installed backward, or missing then the fuel in the pressure line will move toward the engines when its not on its pressure push cycle, and the when the pressure line is pushing pressure into the tank the check valve will stop it from going to the tank and act like the tank is already up to pressure.


Another option is the check vlave could be sticking from gummed up fuel and oil. You can pump raw fuel through them and this will usually un-stick a gummed up one.

Troy Newman
Team YS

Thanks Troy I will check all of these things tommorow,, something I forgot to mention, I have the engine mounted inverted,, and lets say I turn it over to prime it, it runs ABUNCH of fuel out of the exhaust pipe,, almost like the fuel line hooked to a muffler like on a saito or whatever, but it just runs out of the exhaust,, for a second until I start it,, ????????????????????????

Plumbing is not correct. Double check to make sure the check valve is attached in the proper line and in the proper direction. Then make sure the plumbing matches the diagram. I think you likely have plumbing messed up...they just don't dump fuel like that..

If the regulator was staying open all the time the fuel would run from the carb not the muffler.

The enigne should likely not need any prime to get it started...maybe if its been sitting for a long time....


Inverted mounting has no effect on these engines. If they are upright you might be able to run them a little richer at idle that if they are inverted that is the only difference upright to inverted mounting.

Troy Newman
Team YS

I will check it out and let you know Troy, thanks,

Looking at the front of the motor, there are two nipples stuck straight up ,,, one is pressure and one is intake,, which one is what, I can turn the prop over and the one on the right, looking at the front of the engine pumps fuel out,,,

The nipple on the exhaust side of the engine is fuel IN...the nipple on the Needle Valve side of the engine is Pressure back to the tank.

The one on needle valve side toward the rear of the pressure line out...(inline with the cam gear) connects to the nipple that is back at the Needle Valve assembly.


The main thin is the connections up front. The one on the exhaust side is fuel IN the one on the needle side is pressure out.


The check vlave installs with the arrow point toward the tank. This allows pressure into the tank and stops the pressure from coming back toward the engine.

here is the manual that came with the engine

http://www.yspartsandservice.com/pdf/FZ110.pdf


Troy Newman
Team YS

Also,
The notch cut into the check valve to indicate direction of flow can be deceiving.
The notch has a short end and a long end. The long end should be directed toward the tank.
In any event, I always blow thru them to do a manual check of the proper direction.

I had the lines crossed guys,, so maybe that will fix the problem, I am using a new Perry check valve,, it seems to work fine doing the blow through test so I will try it for now,, and maybe now it will crank up and run right tonight,,

You will want to use the YS check valve....The Perry may work, But the YS check have a fairly low pressure to close. many of the check valves on the market have a ball bearing in them and it takes too much pressure to close them off. This doesn't allow for the engine to build pressure.


This could also be your problem. I have no experience with the perry...but if it doesn't close fast enough (blow test is not good enough) then it will likley not close until pressure gets higher in the tank. Since the pressure ina YS builds slowly you need the YS style of check valve.


Troy Newman
Team YS

Hey Troy, I got the YS running decent,(had the fuel lines crossed), the only problem now is the low - mid range,, When I start it up , even with the glow heat on the engine, when I try to transistion from idle on up ,, it will fall on its face, I will quickly back it back down to idle and it will catch up and idle decent,, but I if it stays at a low idle to long it will cut off,,, ,,,,,, , , then I can crank it back,,, I can fly it around fine, but when I back it down to a high idle to keep it running it is to high of a idle,, but when I back it down on final approach to a slow idle to land it will cut off by the time it gets to the runway,, just wondering,,, to me it sounds lean on the low it,, it doesn't really burble when you advance the throttle after you start it,, it will just almost cutoff, then I can quickly bring it back down to idle and it will sound fine,, but the high end(if I can get the throttle to take that far) sounds good,,,, anyway, thanks for any advice Troy

Yes likely lean on the low end... Maybe the regulator is a little lean too.


Regulator is set at 4000rpm....surging up and down is lean, and slowly loading up is rich. Regulator works the same as the HS needle In (CW) is lean and out (CCW)is Rich.


Then drop it into a low idle....2000rpm or as close as you can get, but try to get it less than 2400 at least...goal is 2000rpm....If it drops to a higher rpm then will slowly settle to the lower rpm its lean. If it drops to the 2000rpm right away and then surges up and down its lean. If it drops to an idle then slowly loads up and quits then its rich. The air bleed screw on the carb is OUT (CCW) for Leaner and IN (CW) for richer.

A tell tail sign of too lean on the regulator or low end is a sudden quit on throttle up. a ZiiiiiiiiiiP! and then it catches and goes or just dies. If its rich on the low end or regulator is will chuuuuug-chuggg-chuc-chug-chug and eventually clean out and throttle up. rarely will it stumble on a throttle up when its rich...it will just take a while to clean out. The quick stumble is a sign of too lean.

Troy Newman
Team YS

Thanks Troy I will play with it tonight,, thanks, I will let you know,,

Could also still be the perry check valve. If it leans out on the low end, you could be losing pressure in the tank when the throttle is brought back down.

OK guys got back to the tuning today,, I have got this baby tuned great now,, I read all instructions and all threads and used Troy Newmans advice,, I have her idling at about 2030 rpms and it sounds great,, I can let it set for minutes and nail the throttle and it shoots wideopen in a heart beat,, I put a 14x12 apc and it peaked at 9080 rpms and I riched it up to 8750rpms,, to that should be good,, dont' you think Troy,, , I have it running like a sewing machine and I think I am going to love this YS,,

That will work. The RPM are a little low only about 200 or so. ...but this could be various things such as fuel choice and so on. It will work fine at those rpms.


Troy Newman
Team YS

THX

Hi Troy, is it necessary to have the engine idling at exactly 2000rpm or lower for reliable flight and will it load up if you set the idling speed higher? The way its explained, the engine is on vacuum feed below 2000rpm and pressure above that.
I've got mine down to 1850rpm reliably on ground but worried about a flameout in midair as our flying site is not user friendly other than the landing strip!
Thanks

Not sure when Troy will pick this up, he's usually pretty quick with answers.

But I'll throw out a thought or two for you based on my experience with the 110's; once broken in mine will idle quite nicely in the 1700 RPM range when running 30% CoolPower fuel. The higher nitro content fuel not only produces higher peak RPM but allows them to idle slower and the needle settings are not quite as touchy. I had to get mine idled down or the airplanes they are mounted on would taxi off on the asphalt taxiway's and runway at our field. My Funtana 90 especially likes this lower idle RPM for landing...

I too was nervous about it quitting in flight so I used to just bump up the throttle trim three clicks (or beeps depending on your radio) before takeoff and back it down again for landing. Then when I started flying gassers and all, or most all, of the guys run a mix for what I call a flight idle on their IMAC stuff. Just do a throttle-throttle mix on your radio kicking up the idle to whatever makes you feel comfortable and kick it up before takeoff, and down to land.

Works great and adds some confidence/error margine for you, try it or the clicking the trim up for flight.

The reason I state the 2000rpm is as you said Togatoga the engine is on vacuum at 2000rpm and below. SO this is one reason that 2000rpm is the idle. The other reason is at 2000rpm the throttle barrel is closed enough that the air bleed screw is actually working because the barrel is closed far enough...that Air bleed is actually letting air past. As the barrel rotates and opens up the air bleed screw becomes non effective because the barrel already is letting air-fuel mixture past so it doesn't go through the air bleed hole. The low end adjustment just controls the size of that air bleed hole.


So if you idle is up at 2600rpm the air bleed is not really working anyway and any adjustment you make to it will have little to no affect on the mixture setting for the engine.

NOW that all being say. Once you get the engine set at the 2000rpm for tuning the mixtures then you can run your idle at just about anything you want. 2500rpm is fine. 1800rpm is fine. You want it high enough that it will not quit on you. This can be affected by the quality or the age of the glow plug. As the plugs age while running in the engine idle performance will suffer.

Another note 2000rpm is pretty low. I have seen the engine idle lower like posted above but I tend to pick 2000rpm as my rpm for idle.

An idle up mix or condition in the radio is a way around this....so you have a higher idle in the air while flying and then lower it down to a super low idle to land with. That works. With a properly set mixture and good glow plug.....You should be able to to maintain any idle from at least 2000rpm up. The engine should run there for a extended period of time and then transition like normal. This is where the YS engine excel and outperform most other engines on the market. Basically on the newer YS engines you have a 3 setting mixture. HS, Regulator for midrange and then the air bleed for low speed to fine tune the idle mixture. Properly setup I have seen engine idle at 2000rpm for 10mins and then transition perfectly up through midrange to full throttle.

Troy Newman
Team YS

Thanks very much for answer and the tip. Will program in the idle up feature for peace of mind.