MarkHolbrook

Hi All,

I have a Magnum 61 two stroke ABC that is fairly new. I've probably got 6 tank fulls through it running EXTREMELY rich as the manual suggests.

Now I'm trying to get a little better idle performance out of it. Here is where I'm struggling. Currently all settings are pretty much factory except for the main needle which has gone in about 1/2 a turn.

It is still running really rich on the high end but it will keep running. In flight if I reduce to 1/2 throttle it will quit. So do I need to richen or lean the idle screw and if so how much?

Another hint, when it idles (with the glow plug adapter on) and I advance the throttle it will really lug and spit fuel then eventually it will begin to rev up. This sounds like the idle is too rich.

However this seems contrary to something said in the manual... "If the engine quits when the throttle is advanced the idle mixture is too lean".

I understand that breakin will take a long time and I'm really not looking for a great idle at this point. I just want to be able to reduce power in flight to 1/2 or 1/3 throttle without it quitting.

Mark

daveopam

My Feedback: (9)

It sound rich to my. On a lean setting ,like the manual is talking about, it will pick up some rpm when you advance the throttle then die. It won't sputter. You should be able to adjust the low end 1/8 turn at a time while at idle. Then reset the high end. You might also put in a hotter plug. maybe an OS type "F".
When it dies on you it's swamping the plug. A little hotter plug wil help some. Alot of companies
set the needles rich from the factory. This keeps people from burning them up in the first five minutes.
Personally on an ABC after 6 tanks of fuel I would say it's 95% broken in. ABC motors don't like to run real rich.
They need the heat to expand the piston and make a good seal. later daveo

RaceCity

Daveo makes a good point regarding running the ABC engine "too rich"...(ie: Slobbering 4C rich). It'd be faster to just take a hammer and file to the piston,liner and connecting rod.

The ABC engine needs to come up to a near optimum temp quickly to allow the sleeve to expand properly. If this doesn't happen there's a lot of interference near TDC that will quickly damage the piston/sleeve plating and pound the daylights out of the rod.


With a new out-of-the-box ABC engine...the needle should be set just past the 2C/4C break....just a click on the lean side. Run the motor for a minute like this...shut it off...let it cool completely. Repeating this 5 or 6 times then gradually extending the run time of the engine until it can be leaned to near-maximum power and HOLD this setting without sagging/overheating.

THEN the engine is broken in. Otherwise...it's likely to be just broken.

'Nite