engine tuning question
 

I am new to RC airplanes. I was given an Eagle 2 ARF as a present a few years back. My dad gave me a K&B .40 engine that has never been used but it is over 10 years old. Is there anything wrong with a never used engine that old? I mounted it to my bench the other day to test it. It started fine but I am having trouble adjusting the fuel to air ratio. It was running super rich at first (lots of fuel coming out exhaust and it was dark) but got it to a more acceptable level. What should my exhaust be like? I am still getting some excess fuel coming out...it is minor though and it is clear. (I am using a 10% fuel) Any advice? Thanks in advance.

engine tuning question
 

You need to do a proper break-in on it. You can't just take a new engine, lean it out, and expect it to run perfectly. It will take some time and some patience to get that engine properly broken-in.

What kind of engine is it? Is that one ringed? Do you have the instructions for it?

engine tuning question
 

A 10 year old K&B 40 NEEDS to run rich, "lots of fuel coming out exhaust and it was dark". Running it lean can ruin it.

You want it "blubbering" rich (called 4 cycling) at full throttle for the first full tank at least. Then, you can lean it out a little, just until it starts to break into a 2 cycle run. (Preferably back and forth between 2 and 4.) Run it this way for another tank or two.

For the next couple of tanks you can run it on the rich side of lean. (All of this at full throttle.)

Once you have at least 3 to 4 tanks through, 4 to 5 is better, you CAN start running it leaner. "I am still getting some excess fuel coming out...it is minor though and it is clear." May be too lean.

If the engine is bench mounted, the easiest way to determine if it's too lean is to "pinch" the line feeding the carb. If the engine just quits, it's too lean. If it picks up some RPM before it quits, it's probably about right.

You don't EVER want to run your engine at peak RPM because once in the air they unload a bit and lean out further. Can do a lot of damage quickly. Tune it to peak, then back off 400 - 500 RPM. If you do, the engine will last for years. (If you don't plant it first. :( )
Dennis-

engine tuning question
 

I don't have instructions for it. My Dad got the engine as a gift as he wanted to get into RC planes but never did. I'm kind of doing this blind.

It's a K&B .40 engine. I'll either get a model numbe off of it or take a picture.

So a 4 cycle run is just running it super rich? Did I understand that correctly? and a 2 cycle run is running it more lean?

How do you determine what RPM you are running at?

Thanks for the information about how to break in the engine properly. I greatly appreciate it.

engine tuning question
 

Dennis obviously knows what he's talking about, follow his advice!

You know what RPM the engine is running at with a tachometer...

You don't NEED a tach, but they always help. It's easy to hear the engine speed up and slow down. A 400-500 RPM drop is basically just enough to hear it noticably slow down...

http://www2.towerhobbies.com/cgi-bin...?&I=LXPT31&P=7

engine tuning question
 

Thanks for the information and advice. I ran 5 tanks through the engine today. I had it running so rich I think that it was blowing out more fuel than it was actually burning. I ran it at pretty low RPMs when I did this. As I went through the tanks, I noticed that it ran smoother at the same throttle position.

Is there anything else that I need to do?

Now that my engine is broken in, when I get the air/fuel mixture set, will I still get some fuel blowing out? Will this affect my aircraft at all (ie fuel on the aircraft skin)?

Also, would it be worth it to buy a newer engine down the road? How do the new engines run differently?

Thanks for being patient with all of my questions!

engine tuning question
 

Medium,
Don't ever apologize for asking questions. It's about the best way to learn anything.

You will get excess fuel/oil blowing out the exhaust of every glow engine, it's normal. The residue is a pain to clean off the aircraft, and most people use some form of homemade cleaner and paper towels. (A mix of Windex with ammonia, and Fantastic or 409 works for me.) It should not harm covering or paints that are made for RC aircraft, most are fuel proof. (Some decals and graphics will lift at the edges though.) DO be sure to coat all exposed wood with epoxy though. The oil will soak into wood and soften it. :(

I'd say 'maybe' to the newer engine if you can afford it. K&B 40's (older ones at least) have a reputation for being finicky. The carbs get to be an issue over time too.

An OS 46 FX is one of the best engines out there right now, but also on the expensive side. Some swear by the Thunder Tiger .46 Pro (I think). It's supposed to also run reliably and produce good power at less money.

BUT! If the K&B runs okay for you, stick with it for now. Wait until you learn more before you invest. You may move on to a second plane quickly and want a 60 size. Who knows. :D

Your next step should be to find a local club and an instructor. You don't want to try flying on your own, it's much more difficult than anyone ever expects.

This site can help you locate clubs in your area, and most clubs have instructors who will teach you without cost.

http://modelaircraft.org/templates/ama/

Dennis-

engine tuning question
 

Dennis,

Thanks for all of the information, I greatly appreciate it.

My plane is almost done (Eagle 2 ARF) and I'm want to get some instruction this fall.

With your advice, I think I'm going to stick with the engine I have for now and see how it works out for me. I can upgrade in the future.

Jason

engine tuning question
 

With out going in to details, the break-in procedure metioned above is absolutely correct for engines like your old K&B.

BUT, if you do get a new engine like the OS .46FX or the TT .46Pro, there is a different break-in procedure to use. If you use the same technique on those engines (ABC or ABN engines), you can actaully cause damage.

So, before doing break-in, you need to know what kind of engine it is. There have been lots of threads on there about engine break-in and the different ways to do it, so I wont' repeat it now.

engine tuning question
 

Real good point Kirk! I probably should have mentioned it when I recommended those engines, but frankly, never thought of it!

Jason,
If you buy one of those engines, ask before you try to break it in.
Dennis-