Racinrc14

My Feedback: (7)

Hello fellas,

Acquired a .91AC for a H9 Katana right here on RCU. It looked like new (came in original box, no staining, solid compression, smooth bearings, clean valves and piston), so I am proceeding as if new. I installed it in the airframe, plumbed it as per the instructions (with Y.S. check valve), and set both needles to 1 1/2 turns out from closed, and set about running it in. VP 15% nitro, 18% oil, new O.S. #F plug, APC 14 x 8, uncowled. Here's what I'm experiencing: Start the engine, let it idle a bit, then run it up to set the high speed needle. It will not 'clear out' until I have the HS needle in one full turn (which is 1/2 turn out from closed), then, it 'catches up' and over leans, preignites, and spins the prop off. I have tried to 'sneak up' on the HS adjustment, only to have it do the very same thing. I don't want to damage this engine with preignition, but it will not clear out (8-stroking, as it were, if a 2-stroke running rich is called 4-stroking) no matter how I approach the HS adjustment. It idles beautifully around 2100 RPM, and will idle that way for a full tank of fuel if you let it. This is an older engine, so could it be the gaskets? What are the symptoms of a faulty or mal-adjusted regulator? Thanks for the help, I really want to fly this plane this weekend.

-Tommy

tande

My Feedback: (48)

Well..... tough to trouble/shoot over the internet, but.....the fact that it runs at all, leads to the very first test......with engine stopped, does the fuel supply system hold decent pressure? ( tank pressure IS the fuel delivery process, there is NO pump).....a properly operating system will hold tank pressure for days if not weeks..... after this we can move on to fuel regulator issues (disassemble & clean) & then on to "Air/leaks" (gaskets etc.)......FWIW.....

Jimmy Skids

My Feedback: (2)

Tommy,
I am not sure what your problem is for sure, but let me offer this up to hopefully point you in the right direction.

When starting I use the following procedure. Using a fuel with 20% nitro minimum (I prefer 25-30% normally for sport flying) I will first prime the motor by opening the throttle with no glow ignitor aplied to the plug and spin the prop for 10 seconds. Then I will close throttle to idle position and apply ignitor. I will start the engine with the starter, then allow the motor to "warm-up" over a period of about a minute at 1/3 throttle. Once the motor is warmed up I will slowly advance the throttle to full open and then tune the high speed needle.

Just guessing here, but I would believe that you should start with your fuel and see if the problem persists.

Good Luck,
Jimmy Skids

Racinrc14

My Feedback: (7)

Thanks for the tips guys.

I did manage to finally get it running, but not what I would say is up to the reputation of these YS engines. I'm pretty sure I had a leaking gasket somewhere. The fuel system holds pressure for at least overnight, and it starts very easily by hand. Here's what I have done thus far:

ALL new gaskets (YSE2020)
ALL new O-rings (YSE2090 I think) including the throttle barrel seal
ALL new regulator components (spring, plunger, and diaphragm)

Here is what it is now doing: Starts easily, runs up to max RPM (minus a couple hundred, as per the instructions), return to idle, everything is fine for a while. After about a minute of running at various throttle settings (flying), the needles (both high and low) become inconsistent, i.e. run it up once and all is well, run it up again and it wont clear itself out without leaning the high end a little more. Then, after getting it to run up ok a few times, it richens up again starting the whole process over. The high speed needle is not 'drifting', as it is in the same position as before adjustment as witnessed by the location of the set screw in the end of the needle. The low speed needle also seems to be somewhat un-responsive to changes (starting with the factory 1 1/2 turns out). Also, I observed fuel running out of the carb after shutting it down (remember, all NEW regulator compolnents). A catastrophic flutter problem on the last flight prevented me from further frustration, but the airframe has been repaired and is ready for more engine tuning. I'm looking for advice on what changes to make next.

I cannot find any good, specific instruction on how or why to adjust the regulator, other than to 'just set the screw flush with the body', which it is. Could this be an issue?

Thanks for the advice, and sorry for the novel, but I'm trying to give you fellas as much info. as I can.

-Tommy

Jimmy Skids

My Feedback: (2)

If you are dripping fuel after shut down you need to close the regulator some. I would suggest about 1/8 of a turn at a time. Lastly you did not mention if you have tried a different fuel yet. I would strongly recommend something with a bit more nitro. Many like to run these motors on cool power 30% helicopter fuel by Morgan's. It might save you some frustration if you pick up a gallon and start there. Also, the higher nitro content makes the motor a bit easier to needle.

Lastly I would also suggest that you remove the regulator and check it to make sure there isn't any debris in it.

Good luck,
Jimmy Skids

Racinrc14

My Feedback: (7)

Jimmy,

I took the regulator apart before I posted that and found nothing in the cavity or orifices. I was hoping to see something installed incorrectly but alas, it looked to me like I installed everything as intended. As for the fuel, my other four strokes (I have several, Saitos and an older O.S. .70) run great on this VP 15% fuel. I'll stop by the LHS tonight and see if he has any 30%, but I fear I may have to make a run to Dallas (Im at Sheppard AFB for training for the next four months, and the LHS here is nice, but not fully stocked) for fuel.

Thanks again, I'll try the regulator bit tonight before I go to the LHS to see if there is any change.
-Tommy