Today I lost a plane do to my Moki 2.10 leaning out. I had just pulled into a hover and about 3-4 seconds later it died. I have been running the engine for about 6 months now with no problems. Today is the first day I ever ran it in the cold. Our high today was
about 43 degrees. I did have to richen the high end quite a bit before I flew it. Is there a solution to this engine running lean when pointed vertical? Someone at my field mentioned a cline regulator.

Greg

Cold air is more dense than warm air. It necessarily requires a richer setting.

The solution to your problem is not to run the needle for MAX rpm. Not only in the cool
weather, but in any weather.

The engine will lean out when it's 120F outside just as it would when it's 20F.

Conservative needle settings are the ticket. Tune for peak, then back off a few hundred rpm

'Race

Thanks,

Did that, but it still went lean in the hover. I richened it about 3/4 turn beyond where I normally fly it. It was to the point where when I richened it further the RPM would decrease.

Greg

Well..that's kind of the idea when you richen any motor. The rpm will decrease.

"Normal" is never a fixed setting with any motor. They're very dependent on atmospheric
conditions, and temperature plays a HUGE role with many aspects of an engine/airplanes performance.

Lean your motor for peak, and then richen the setting by 2-300 rpm. You have to do this, or....else.

Strange you got all the way to Moki 2.1's before you learned this?

'Race

Did ya do the pinch test, did you set the idle mixture also, did the engine die durning transition. Moki's are very reliable engines if tuned correctly, sorry ya dinked your bird.

Greg, one thing you might want to look at, is the low speed disk moving too freely, did it rotate by itself past the magic 15 degree point? Mine got loose over time and drove me nuts before I found it.

Ed M.

"Strange you got all the way to Moki 2.1's before you learned this?"

Race,

I don't see what you think its strange. I am fairly new at the hobby (2 years) , but I have owned enough engines to be beyond the novice stage. I've been flying the moki for 6 months now. You assume I didn't adjust the engine prior to flying. The moki is very temperamental to changes in temperature and air density, more sensitive than any other engine I have owned. As I said in my previous post, before I flew, I richened the high end until the RPMs started to decrease, and the engine actually ran rich during normal flight with airspeed. Even on uplines with airspeed the engine showed no signs of quitting or sputtering. It was only when I entered the hover did the engine die after 3-4 seconds. Never had this problem when flying in warmer weather. Just wondering would the cline regulator help maintain a more consistent fuel flow.

Ed

Low end needle seems fine and is fairly tight. It maintains its setting.

Thanks,

Greg

First off...a pump WOULD alleviate inconsistencies in the fuel delivery...provided the plumbing can
supply enough fuel in the first place.

The 2.1 is a beastie of a motor...it has an appetite for fuel that is going to require a large ID fuel tubing
be used all the way from the carb inlet to the clunk in the tank. LOTS of big STs fell prey to this overlooked
element.

The motor might run just fine in normal flight attitudes, but once the nose is brought up straight and held
there for a period of time...gravity adds further to the reduction in fuel flow, and you run into problems.

Many r/c carbs do not meter linearily throughout the rpm range. If it was set slightly rich at WOT, and gets a little
leaner in the mids...it'll die.

Set your needles, Have a helper hold the model upright...like a hover. Run the throttle smoothly through the rpm
range and observe what happens. See if you can duplicate the problem safely on the ground.

Adequate fuel flow capacity first...Pump/Regulator second.

'Race

Good Idea race. I will first try to duplicate on the ground by pointing the nose up and transitioning through all throttle settings. Hopefully it will die. Next step I guess is to make sure there is no debris in the carbeuretor jets. If that looks good then I will go ahead and get the cline regulator. After talking to Gerard interprises, in am now 90% sure that will alleviate my problems assuming there is nothing partially blocking the fuel system. I will also use larger diameter tubing. I think the reason it didn't quit when flying on an upline versus in a hover (same orientation) is because when I was on the uplines the throttle was higher...creating more muffler pressure. However, in the hover the throttle setting was much less... resulting in insufficient muffler pressure and without the aid of the fuel pressure, there just wasn't enough fuel delivery.

Greg

we always choose the shortest root - get a perryv30 and big fuel tubing a drilled clunk and you will save on expensive repair or total loss for only spending well under 50$ and a little time.

Columbo...

There ya go. You're going in the right direction.

If you need a pump...so be it. (I am just averse to added complexity if it's possible to avoid it)

It can be VERY revealing to hold your model vertical and run through the rpm range slowly. A motor
that is otherswise a real sweetheart can suddenly have all sorts of problems.

The hover attitude is a worst case scenario for the motor and it's fuel system.

Good Luck with it!

if this happened once, even though it is major, it may be a one time thing. I run the moki 2.10 on my edge. I know it is severly sensitive to fuels and plugs. I run all day long @ 5% Omega. The low end is so sensitive that its rediculas but after my second flight I havent had any problems what so ever. No matter what the manuver. I have been in all kinds of temps. I run the OS #3 plug. no pump. Medium tubing, nothing special to the clunk in the tank. my tank is mounted directly behind the engine on the centerline getting pressure from the bisson pitts muffler. I did have some grass garbage in the carb once and it spit for an instance and then worked through it. Just My 2 cents worth.

Greg,
another thing to consider is the fuel your using. Engines from a far where nitro is on the high dollar side tend to need either VERY little nitro, or even none at all. I've had GMS's, MVVS's and even Norvel's act crazy with too high of nitro fuels. They act is if your are chasing the needle, and never can find the right setting. When you use too high of nitro for a given engine, it makes the needle settings become critical.

I don't know if this is a factor in your case, but it is good for one to know and I hope it will help.
Dennis

Thanks Dennis,

I use 0% Nitro.

Greg

I don't know why nobody has mentioned this but one thing I like to do when there have been major changes in the weather or atmospheric conditions that required changes in needle valve settings is to keep the plane up high while running through some nose high maneuvers. A flame-out at high altitude tends not to have such disastrous effects as one at low altitude in a nose high attitude. [8D][8D]

RJ

I first tested it at a higher altitude. The reason being is because the day before I almost lost it when the engine sagged as I pulled up to a hover. In that case the power came back before I hit ground, and I was able to recover. So I was aware of the potential problem. I thought that the reason it quit the previous day was a result of too lean of a setting, so I richened it. The next day after richening it, I tested it fairly high first and it showed no signs of quitting. Later in the flight I brought it lower and had just pulled up and 3-4 seconds later it died. Maybe the reason it didn't quit during the high altitude hover test is because there was more fuel in the tank and the engine was running richer. Later as I brought it lower, there was less fuel in the tank and the engine was most likely running leaner.

Several days before when the temperature was about 15 degrees warmer, the engine would run on the leaner setting and I was able to hover just off the deck for 20-30 seconds. I think that since the temperature yesterday was colder and the air more dense, when pointed vertical at lower throttle, the muffler pressure just couln't keep up with the demand for fuel required by the richer setting. So I guess bottom line is in colder weather it is more difficult for muffler pressure alone to keep up with the demand for fuel than in warmer weather in these giant glow engines. When I tip test it on the ground I will make sure there is little fuel in the tank.

Greg

You're probably right........... RJ