esbenbach

Hello

First of all I want to say that I am not good at english.

I have a problem with my YS-110 [:@] that is the fueltube between the pump (i think) and the carburator has small airbubbles, but their aren't air in the tube between the tank and the engine. Are there someone who know how I can solve this problem?

Esben

petec

My Feedback: (58)

If they are really tiny bubbles and are there only at idle it could be a function of the fuel not being under pressure on the carb side of the regulator. If they are bigger bubbles and there all the time I'd be lookng for a leak in the fuel system or a bad seal around the regulator.

42etus

My Feedback: (2)

There may not be a problem. It is completely normal to have SOME bubbles in that fuel line. How is the engine running? If it is running badly and there is an excess of bubbles, then you need to check for leaks or a small hole in the diaphram. How old is the engine?

esbenbach

Thank you for the answers. The engine is new (my first YS ) and has run 1 gallion, and it runs realy badly, when it hit half power, it try to turn backwards, and runs irregular . I can make i video tomorrow, i really dont no what to do with this engine . I use i Tetra tank.
In idle it is running very wel, but when it increase RPM [:@].....

petec

My Feedback: (58)

If you are getting big bubbles then the engine will go lean when you advance the throttle which will cause the engine to backfire. In which case you need to find the source of the leak.

greenred

I have a new YS-140 that I have run maybe a third of a gallon of fuel through and it is doing the same as what has been described here. It start fine, spins a 16 x 8 APC prop just over 8000 rpm, is totally adjustable with the needle valve on the top end but will not idle worth a hoot.

When the engine is running there is a fair amount of air bubbles in the line from the regulator to the carb. As long as the rpms are up it seems to run fine but when you allow it to go to idle it will idle high for about 10 to 15 seconds and then the idle will drop until it quits. As it is idling, (just before it quits) the air bubbles in the line start to outnumber the amount of fuel in the line and pretty much looks like foam.

No adjustment of the low speed screw or regulator screw makes any difference. To get the engine to maintain an idle the idle that the engine holds for the 10 to 15 seconds after coming down from higher rpms needs to be set at about 3000 rpm! With this high an idle the plane would not be landable and anything lower the engine stalls.

I have taken the regulator apart and inspected all the components and I cannot find anything obvious wrong!

??????????????????????????

GRR

tz250w

I'm having the same problem here with the 110FZ (not S). I just acquired this engine after it took a swim in a river with its previous owner... doh. I disassembled it within minutes after the dive, cleaned it with fuel and have run two tanks through it on the bench. Everything looks okay visually but I get the bubbles and things go nuts. I noticed releasing the pressure from the fuel tank will let it run well again for a few minutes until the bubbles start (lots of bubbles) and then it starts coughing and flaming out.

tz250w

Just curious... I haven't removed the fuel line nipples yet. The regulator gasket looks fine, as does the diaphram. Where else could it be sucking air (fuel lines all new)?

Or could this be a matter of too much blow by?

dmccormick001

Is this engine a 1.40 Sport? If so, there's a known issue with the carb barrel that may be causing you some problems. It makes it impossible to get the engine to idle smoothly. If it is a 1.40 Sport, I'll detail for you how you can determine if your engine is one of the ones affected, and how you can fix it. It's a factory error in production, but it isn't hard to correct.

For the other guy who started this thread, Esben, as has already been said, a small number of air bubbles, small air bubbles, in the fuel line between the regulator and carb is completely normal. Rather than worrying about them, decribe to us exactly what the engine is doing wrong, and we may be able to help you figure it out. If your engine is idling well, try making the mid-range mixture a little richer by turning the screw on the regulator out (counter-clockwise) about 1/8th of a turn at a time. It sounds like the engine is starving for fuel when you advance the throttle.

For tz250w, it sounds to me like your engine may set too rich. If releasing pressure from the tank makes it run better, then the regulator is probably set too rich, causing the engine to flood. Start with the screw flush with the top of the regulator, and then try turning your regulator clockwise a little, just about 1/8th of a turn at a time, until you see improvement. And you shouldn't be looking for places where the fuel system could be "sucking air". The fuel system is pressurized everywhere, from the diapragm to the tank, and back to the diapragm. On the side where the check valve is located, the sytem is pressurized from the crankcase, so those lines have positive pressure (air) going to the tank, and the lines coming from the tank back to the regulator contain fuel that's under pressure, so any leak in either of them will produce either air or fuel leaking out of the system. Likewise, the line going from the regulator to the carb is also under pressure except when the engine is idling. If the gasket under the regulator body looks good, and you've double-checked the check valve to make sure it's facing the right way, then your problem is most likely due to incorrect mixture settings, so take your time and make small adjustments until you get it running right. These engines are very difficult to get right, but once you do, they will run hour after hour with no adjustments, and perform like nothing else.

David