Engine Tuning Question
 

So the trainer is assembled and I took it outside to fire up the engine and break it in. This went well, it started quickly and I followed the manufacturer's break-in procedure. So now I THINK it's running quite well but my question is how low should it be able to idle without stalling? Should it be so low that the model doesn't roll at idle? Because right now I have to hold it firmly even at the lowest that I can get it to reliably idle. I do intend to have an instructor check it out prior to flying.

BTW-it's a .40 sized trainer w/ a Magnum XLS .46 engine

Thanks!

RE: Engine Tuning Question
 

Sounds more like high idle than a tuning problem. Your instructor will be able to sort this out. Make sure you tell him before he fires up the engine ;)

RE: Engine Tuning Question
 

You should have your idle set so the plane doesnt roll.

RE: Engine Tuning Question
 

It's also worth keeping in mind a couple of things.

First, idle reliability improves with run time. I doubt you have enough time on the engine for the idle to have really become as good as it will be.

Second, idle rpm varies with prop diameter. Heavier and longer props have more flywheel effect, allowing the engine to idle lower.

Third, the prop brand, pitch, and diameter will affect how much thrust the engine is producing at idle, which basically is how hard the engine is trying to make the airplane roll.

Fourth, what surface your plane is on, and how friction-free your wheels are will affect how hard the airplane fights back against the engine to keep from rolling.

All that put together means that you might or might not be able to get a plane to stop moving on a smooth paved surface, but most planes will stop moving on grass easily. If your on pavement, you can always add a little friction to the wheels by moving the wheel collars against the wheels a little.

Oh, as for actualy rpm, anything below 2k is pretty good for most new 2-stroke engines in that size, some can get close to 1k, depending on the details.

RE: Engine Tuning Question
 

depends, what is it "rolling" on??

grass no roll, concrete or tar youll probably get some roll even at low idle

RE: Engine Tuning Question
 

Move your idle trim down to see if it slows down further.

RE: Engine Tuning Question
 

Montague has said it all, so re-read his post...............

Jetts