Hi,

I run my YS 160DZ with a Mejslik 18x10 prop turning at around 8600 rpm on CP Heli 30%. The engine runs like a pro but recently behaves a bit strange. My needle valve used to be 1.5+ clicks out, a bit rich but the temperature in Greece is high so I thought that it would be good to run it rich. The other day in the second loop of the two outside loops of P09 at nearly full throttle the engine stopped for a second and then continued, this happened twice. So what I did was to lean the mix at 1 1/4+3 clicks and richen the regulator by turning clockwise a tiny bit. Since then I do not have any issues.

However since then, there were some cases that the pump would not pull fuel out of the tank when I rotated the prop by hand, it used to pull fuel very easily in the past. Now needs to be turned with the starter. This happens mainly on very hot parts of the day. When the pump is cold seems to be ok, it can pull fuel by hand rotating. Is there a particular reason for that? Do you believe I should change the pump diaphragm?

Also my YS 170 DZ that I have on another plane has now about 1.5-2 gallons and works pretty well , I followed Troy's in procedure. However seems a bit oily when I remove the under cowl from the plane, my needle there should be 1.5+ turns out. Do you think this oli coming from the carb? I thought initially that was coming from the NRV valve on the head but seems ok. What else should I check?

Thanks in advance ,

Nikos

Nikos,

As delivered from the factory, the fuel line between the regulator and the carburettor on DZ's runs very close to the cylinder head. On very hot days, especially after the engine has been run, this can cause the fuel to partially vapourise in the line. It is good practice to space the line out slightly from the cylinder head or to enclose it in a short length of insulating material.

As for your oil leaks, there could be a number of sources. It is not unusual for some DZ's to come from the factory with bolts that are not fully tightened. Before installing a new engine in an aeroplane, it is worth setting it up on a test bench. Don't run it for longer than is necessary - just long enough to ensure that the idle is steady and that the engine is running up smoothly and reliably to full revs. Before the engine has fully cooled down, check all the bolts to ensure that they are tight. Your leak may be caused by one or more of the 5 cyliner head bolts that is slightly loose or by a loose bolt in the backplate assembly. "O" rings are the other thing to check, though if the engine is new they should be OK unless they have been nipped during assembly.

Best of luck

Bob

PS:
I am assuming that the seal between your manifold and your exhaust is in good shape!

The oil leak could also be the valve cover. They get out of shape really easy, and can be fixed by re-surfacing using some 1500 - 2000 grit paper and some sort of lubricant on a piece of glass.