Engine Miss-fire

[Shuttle-mad]

Hi

Got a new problem with my heli to solve i am running a sc36 mk11 ringed engine i have been restting all the trims today after rebuilding most of the head assembly the problem is the engine has developed what i can only explain as a miss fire. I have tried screwing the needle valve both in and out i also turned down the slow throttle adjustment screw to try and reduce the amount of unburnt oil from the exhaust. The engine has only seen half gallon of fuel since it was fitted,the fuel is Duraglo 5 with 20% caster oil


Kev

[magnumfuels]

Kev,

Unburned oil is GOOD! Its meant to be that way. I guess you're hovering at the moment so set the engine to the settings in the manual and go fly it. After you land and shut the engine off, stick your finger up against the backplate - it should be tolerably warm. If it is hot then richen ther main needle a little (2 clicks at a time). Then fly it again and check it afterwards - it should be warm immediately after shutting down. If you wait too long after shutting down, then the backplate will warm up as the heat from the head transfers throughout the engine.

HTH

P.S. Isn't there anyone that can help you locally?

[belair]

Hi, just like to say that when you use a OS engine for your heli, you can forget having enginetrouble. That was the advise I got before even buying a heli. I toke the advise and payed a little more but don't have any regrets.

[G-DAVE]

The oil in your model fuel has two functions -
1 - Lubricates the moving parts
2 - Acts as a sort of heat sink, the oil that's pushed out of your engine after the ignition cycle carries heat away with it -- that's good.
There are many options for fuel choice on the Market but a one with 20% castor oil would be at the bottom of mine.
Try Magnum - or Cool Power -or Flair double orange in that order of preference .
Dave

[antsis]

Kev
Can you be more specific. Does it misfire at idle, as you open the throttle or at full power? 2-stroke engines will make a noise when they are running rich whch sounds like a misfire and this is generally known as four-stroking.

I would start with getting the idle smooth and then see how the engine responds as you throttle up. Generally, the main needle is set to 1.25 to 1.5 turns out.If the engine burbles, misfires, 4-strokes, in the mid range, then you idle could be a little rich. On some engines, if you adjust the main needle it can affect the idle as well. I would also recommend starting with 10% nitro. This will help with the slow running.

There is nothing wrong with 20% castor. The drawback with using it is that the piston crown tends to carbon up quite quickly, meaning regular engine cleaning. Many other brands utilise synthetic oils with a small % of castor.