CAP232S

HI all BME Extreme 110 owners,

I would like to know the following: I have bought a brand new BME Extreme 110 engine. I decided to check the carb high and low needle settings
as I recieved it out the box. I have noticed that the low end needle was set to only 1 (one) turn out and the high end needle was set
to 2&1/2 (Two and a half) turns out. This is way out from the factory default setting which should be low end needle to be 1 & 1/4 and the high end needle
should be 1 & 1/2 turns out.

Should I reset the needles to the factory setting or is this normal for the BME Extreme 110 to have these kind of settings?

I live +/- 5800ft above sea level and just want to make sure I have the right needle setting for the BME.
I don`t want to run the engine too lean for the first few flights as it is still brand new and I believe in running
an engine in properly to ensure good life and power from the engine.

Just a little concerned about the needle settings for reliable engine running for the first flight.....
I would like to avoid a dead stick on the first flight due to incorrect needle settings!

Please help. Any feedback shall be greatly appreciated

Marius

Tri-stan

My Feedback: (1)

All BME Engines are test-run before shipping. This is probably where they set the needles on the carburetor to assure it ran properly at their altitude of about 500' ASL. I'd advise just starting the engine and adjusting the carburetor from there. There are no 'Factory' Settings on an engine like this, since the engines the carburetor was originally intended for, basically weedie and chainsaw engines, had much milder porting and ran in a totally different manner. The BME110 has pretty radical porting, and this affects carburetor adjustment. I've seen everything from 1/2-1 1/8 on the low needle and 1-2 1/4 on the high needle, depending on the particular carb (even with the same exact carb type on the same engine) EVERY engine should have the carburetor 'dialed in' before it is flown, and you should run about 1/2 gallon of fuel through the BME to assure everything is working properly and that you have the mixture needles set before you ever fly with the engine.

By the same token, though, I just pulled a 110 off a plane, and it had canister exhausts on it. Needles were 3/4 on the low side, and 1 1/4 on the high side. If you feel that your needles are incorrect, I'd recommend trying the settings I just gave you .. 3/4 low, 1 1/4 high, and going from there. Remember to keep the engine slightly rich on the top end, but not slobbery rich, and to set the low end for a clean, but transition-able idle. Run 50:1 ashless oil for break-in of about 8-10 gallons, then I highly recommend switching to Amsoil Sabre 100:1 oil mixed at 80:1 ratio for the rest of the engines life.

Remember to check your sparkplug color to ascertain the proper mixture. You want a light tan colored center electrode and insulator. Pale-white is too lean, and anything darker than medium grey/brown is too rich. Check this after about an hours running time, and periodically thereafter. You will find that the engine will need to be leaned slightly as it loosens up and breaks in.

A good Break-in prop is the 27-10 BME prop, or a comparably sized Menz-s, Bambula, or other wooden 'wide blade' prop of similar design. You can also start off with the 28-10 Mejzlik CF prop, and never take it off the engine. Shoot for a prop that puts the engine in the 6300-6600 rpm range while running. All the props I listed will do so, with the Menz-s (actually a 26.5 inch diameter prop) spinning in the 6600+ range usually, and the Mejzlik at about 6400 or so. I've run props up to the 29-10 Mejzlik on these engines, with good results, but the 28 inch diameter range, especially the Biela or Mejzlik props, will probably get you the best performance overall.

Hope this helps.

Geistware

My Feedback: (16)

Tri-stan,
Glad to see you are back.
I have another question, I have always been told that you close the throttle then adjust the idle the best setting, then adjust the high end. I can really lean the low end out but I have to open the throttle to do it. What do you recommend. Open the throttle while leaning the idle? Doing it this way I can adjust the idle at the transistion point to keep the mid-range from being too rich.

Tri-stan

My Feedback: (1)

Okay, Geist .. looks like a discussion about Carburetor dynamics is called for.

Two circuits in a carburetor. . Main, and Idle. Both do different things at different throttle settings.

We'll start with the Main. Basically it controls fuel down to the point where airflow through the carburetor is too low to effectively drag gas out of the Main fuel feed Venturi. This is usually below 1/8 total throttle blade opening. If they made the Main capable of flowing gas at lower throttle settings than that, the top end would be restricted, or the fuel curve would go overly rich when you started to get a lot of airflow through the carburetor. So, to enable the engine to idle at lower rpms than about 2000-2500 or so, they add an idle bleed right next to where the throttle blade closes in the carb throat.

Basically what happens with Idle fuel feed is that at a nearly close throttle plate position the air is forced against the small hole for the idle mixture gas, and causes a low pressure area, which pulls fuel into the airstream, allowing the engine to continue running. The farther you open the throttle blade, the less the vacuum on this hole, and the less idle mixture gas you get into the engine. Idle mixture is effective up to about 1/4 throttle at most, at which point the throttle blade opens too far for air to be forced against the outlet, effectively cutting off that source of gas and making the engine depend only on the Main mixture coming from the top portion of the carburetor.

What it sounds like you are doing is getting the throttle blade into a position where the Main fuel feed is crutching the idle mixture as well, basically an off-idle position, not a true idle. It may work, but there are problems involved with it. What you SHOULD be doing is closing the throttle blade as far as possible, and adjusting the low end mixture needle to achieve the lowest possible idle setting, then backing it off a hair (usually about 1/16 turn from that point) and then setting your idle speed to about 1100-1300 rpm. You ridle should sound smooth, but not TOO smooth. An occasional burble or misfire is perfectly fine at idle. We are not trying to have an idling contest here. . we are trying to keep the engine running when we close the throttle while flying, and a slightly richer mixture helps with this because the engine tends to cool down while the plane is gliding, and too lean of a mixture can lead to stumble or even a flameout.

You want to set your Main mixture by checking it at half throttle. You want half throttle to be SMOOTH. . .no burbles, then as you slowly close the throttle to about 2-3 clicks off idle (where the idle mixture will start to come into play) the engine should start to slightly burble or misfire. If it does not, then you are too lean on the top end. Set your top end needle to where the engine just starts to run rough when almost at idle, but not really rough. . its more a slight stumble/burble every second or so at about 2000-2200 rpm than a constant 4-cycling effect. Once you have those two parameters set .. a decent idle, not TOO smooth, and a clean midrange with just a hint of burble toward the bottom of the throttle settings, try a few medium speed transitions from idle-full throttle.You do NOT want to just slam the throttle full open. . first off, the servo is going to take about .2-.25 seconds to make the transition, a lot slower than your thumb moves, and secondly its a BAD idea to ever do that anyway. You want to operate the throttle smoothly at all times. Slamming it open can cause flameouts or rough hesitation as the carburetor tries to get enough gas into the airstream and the engien has to wait for it to arrive so it can run properly. After you've checked it all over. . made sure it transitions smoothly with no hesitation and runs well both at full power and idle, let it cool down and see how it starts. Some engines are a bit cold natured, and will require a couple of restarts to run properly (all my 3W's do this. . just the nature of the engines) If the engine starts well and holds idle even when cold, it's probably just a little on the rich side, and you can play with the needle slightly to lean it out a little more. When you start having problems getting the engine started, due to the mixture making the engine cold natured, open the bottom end 1/16 turn at a time till the problem is resolved, then leave it alone unless you have furhter problems. Always try to set the high end for best transition. . NOT best Power. I have not used a tachmoeter to set a needle in about 3 years now. I do check top rpm from time to time, as well as idle rpm, but as long as I can kill the engine using the throttle trim, and I have a clean, slightly rich, midrange transition, and it starts the way it always has, I don't even bother with a Tach. You can lean an engine to achieve an extra 50-100 rpm on the ground, but it's running characteristics in the air may tend to become questionable, which is why I advocate a slightly rich mixture and setting the engine up for midrange, decent idle, and good transition, instead of overall power numbers. Aftter all, the thinking goes .. if you REALLY need that extra 100 rpm or so, you gotta ask WHY. . if its necessary, then you need a bigger engine. If you are just trying to impress people, well. . that's a different story. I don't concern myself with top-end rpm numbers anymore. . they are not what's important. . what IS important ishow well and dependably the engine runs at all times. N ot tweaking for the last 50-100 rpm will result in a better overall running engine throughout the rest of the flight.

After you get it set up, its must a matter of keeping an eye on it. Mosty gassers seldom require readjustment of the needles.

Hope this helps.

Diablo-RCU

My Feedback: (1)

Here's an alternative method to setting the idle mixture. Set the idle mixture so that you get best acceleration from idle to 1/3rd throttle when you jam the stick from idle to 1/3rd. Diaphragm carbs don't have accelerator pumps. Setting the idle mixture for crisp acceleration results in a slightly rich mixture at idle, not too lean and won't flame out at a bad time. If you set the idle mixture too lean, you can easily hear the motor gasp as you do the acceleration test. If the idle is set too rich, the acceleration is slow and the engine will blubber until it clears the mixture.

CAP232S

HI TRi-Stan,

Thank you so much for the complete explanation you have given. All you have said makes perfect sense!
Thank goodness for people like yourself with such good knowledge and experience with gas motors!!

Once again thanks.

Marius

Tri-stan

My Feedback: (1)

Diablo has a good technique too, Cap232s. Use what works best for you, and keep that engine running smmmooooottttthhhhhhh.

Antique

My Feedback: (4)

Deja Vu all over again You really believe what your first paragraph says ?
The high speed needle controls mixture below 1/8 throttle ?
IF airflow through the carb is too low to "effectively drag gas out of the Main fuel feed venturi" why would adjusting the high speed needle make any difference ?
Last paragraph..Set the high needle so the engine just starts to run rough at 2000 rpm ?
Contradiction maybe ?
I give up

Tri-stan

My Feedback: (1)

Ralph I believe you read that out of context.

"Basically it controls fuel down to the point where airflow through the carburetor is too low to effectively drag gas out of the Main fuel feed Venturi. This is usually below 1/8 total throttle blade opening."

This means that the Main controls fuel flow down to about 1/8 throttle blade opening, below which there is not enough air for the Main to properly work. Above that point it works very well usually. Sorry if I did not properly correlate the two sentences.

Setting the main needle, which is just starting to lose it's effect, so that it no longer dumps fuel properly at this point will give you an accurate indication of just how sensitive the Main jetting is to air flow variatinos. If you are too rich between 1/8-3/8 throttle, it's usually because your top end is too rich (In my experience) and when starting at half throttle, and backing the throttle down, you will run into evidence of a too rich top end mixture at the point where crossover begins to occur, usually in the 2000-2200 (or up to about 2500 sometimes) rpm range. The theory and practice here shows that your main jetting will still be supplying fuel, but the fuel will not be atomizing properly due to lack of airflow, and this will lead to overly sized fuel drops hanging in suspension, puddling in the crankcase, and not burning properly, leading to burbling and an overly rich indication. So, this is a good indication of just how properlyjetted your main jetting is. Just something I've noticed over time, and which has proven to be a very accurate indicator for me.

Geistware

My Feedback: (16)

Thanks Ralph, Kris, and Diablo,
I will say it looks like my engines are run rich. My next question is: I have been told that you always run with a tan plug color. Not black. I have never had a tan plug on my BME. I have had a tan plug on my Brison engines. I adjusted the carb the same way with both engines but with different results. maybe I just got lucky with my Brisons. I guess I will keep leaning the engine until it shows poor transistion or sagging on uplines. For me it is hard to tell if an upline is sagging. Usually the plane does not look like it is slowing down until it is too high to see the pilot in the cockpit. I always contributed this to perception instead of reality.

Tri-stan

My Feedback: (1)

Fatten the bottom and lean the top, Geistware. Do ground run tests to make sure its not too lean at idle with the blade as closed as possible. If the plug is black, and 75% of your mixture comes from the Main jet, its too rich. A rich top end will also cause the idle, where you are trying to set it, to appear rich, and you will be mistakenlyleaning the bottom to try to straighten it out.

Geistware

My Feedback: (16)

Sounds like I will have my work cut out for me during Easter Weekend

Tri-stan

My Feedback: (1)

Just get the idle set first, Geist. . and go from there. It's really a simple 10-15 minute process.

CAP232S

Hi Tri-stan,

Just a follow up after the week-ends flying. Well I tried the settings as they were which was 1 turn low and 2 1/2 high. I did actualy manage to get the engine going on these settings but it was very rough. I flew it like this but it was four stroking all the time. Everybody at the flying field told me to lean it out because it was very bad for a motor to run so rich to the extend that it four strokes.

The motor ran very cool, I could touch the cylinders with bare hands no problem. I did however lean out the motor quite a bit. I have not checked it but I am about 3/4 low and 1 3/4 high. Even on this setting the motor is running rich but I am scared to lean it out further at this stage.

One thing that I think is realy crap, is the one bolt thing for the prop. I replaced the cap screws with spring steel pins hoping this will solve the prop slipping problem but the engine just bent those pins like they were tooth picks!! The prop slipping thing caused the prop to hit the spinner and damaged the the prop slightly. I am going to try the rough sandpaper idea I read somewhere once between the prop and the back plate of the spinner. I dont think this will solve the problem.

This is one area where BME can learn something from the other manufacturers regarding bolting a prop on to an engine.........
If you have any other ideas regarding the prop slipping then please advise.

From the little that I flew I could see that there is awesome power from the motor and cannot wait to try the engine again after leaning it out a bit more.

Well that is it for now
Marius

RTK

My Feedback: (1)

CAP232S- Make sure that the back plate of the spinner has plenty of deep knurling, and really tighten that nut. I have a tru-turn spinner and have not had any problems with slippage as of yet with the stock setup.

Albatross

My Feedback: (7)

CAP232S:

Did somebody talk about propeller slippage? although I don't own a BME 110 yet, that's one of my concerns. I have seen spinners and propellers damaged by this nasty inconvenient. I submitted the same question in this forum as well, here you will found some answers too:

[link=http://www.rcuniverse.com/forum/m_2526295/anchors_2590325/mpage_1/key_/anchor/tm.htm#2590325]BME 110 Owners [/link]

I don't know a lot about engine design, evidently the single bolt propeller along with other weight savings tricks, together are the key behind the weight reduction of this engine, however that's the little something that makes me thing twice about investing in this engine. I am with you I wish I had a BME 110 with 6 bolts to attach the propeller (having same power and same weight), however so far owning and flying my airplane with that engine is just a project.

barryb-RCU

On prop slippage -- pins do nothing but help you align the prop when you put it on. And neither do multiple prop bolts. The only thing that keeps
slippage from happening is tight bolts combined with correct advance.

I've run a Brison 6.4 twin for years with a single bolt hub -- no slippage whatsoever. I've run a DA-100 for years with three of the six bolts (I'm a weight freak)
with no problems. And a DA-50 with two of the four bolts.

Other than too much advance, the problem that causes slippage is compression. Usually compression of the prop. If you're running wood props, you must
re-tighten the prop bolt after the first 5 minutes of running (a very short flight!), then retighten it after each of the next two flights.

Another point of interest -- I've seen a six bolt hub used where all six bolts sheared at a high idle. They did so because they were loose. The bolts
themselves provide almost no torsional strength. It's through compression that they keep it all in one piece.

If you're confident that your prop was tight, look to too much advance as your culprit.

Tired Old Man

My Feedback: (1)

Another note on prop slippage. If the center nut was relatively tight to begin with, if and when it slips it will usually tighten the nut, not loosen. That in itself is a pretty common occurance. If the nut was too loose initially, then coming off would be a natural ocurrance with any kind of a kick back due to excessive advance or a less than energetic flip of the prop

Geistware

My Feedback: (16)

If I am not mistaken, Tim Mills bolts the propeller to the spinner backplate and then uses sand paper between the spinner back plate and engine hub. He doesn't have this problem

byoung466

My Feedback: (16)

To wake this thread up again. I was curious, I have a BME 110 where the engine starts great and has a good clean idle at 1100-1300. Im still learning to set this up as its my second gas engine. Its on JMB cannistors w/ a Biela 28x10 prop.

So advancing the throttle to 1/3 open the engine is very responsive, no hesitation. Advancing the throttle further and/or after taxing out to take off the throttle advance through 1/2 yields a fairly flat result, but the runup in the pits doesnt seem like the top end is too lean.

For me it seems like there is a lean spot in the transition, the engine doesnt burble or pop or anything that to me would seem like a rich low speed needle setting. I have been working the low speed needle richer but it seems OK now. My thinking now is to start taking the main needle richer to see how the transition is affected....make sense?

thanks for any comments.

RTK

My Feedback: (1)

How does it respond in the air??

byoung466

My Feedback: (16)

Similar to on the ground...full power isnt frequently needed or actually much above 1/2 throttle but anything pushed beyond half isnt very responsive. Could also be that I have to much prop on it to early I suppose.

RTK

My Feedback: (1)

First, what do your plugs look like? This can tell you a lot about which way to go.

How does the engine pull at WOT on an up-line?

"Sometimes" the needles can give the false impression of being lean by making the engine bog in mid-range (load up) and you think it is lean.

I would start by leaning the low till it won't transition when goosed to 1/3 throttle, then richen until it will with out hesitation and add just a tab more.
Now before flying and/or testing the "high" end, richen it a good bit. I like to start really rich on the high end then back down.
The low always affects the high and with this engine and carb combination it seem to be more pronounced than in others. I never run my large gas engines for more than a few seconds on the ground at WOT, I have seen too many people do damage this way because the did not realize how lean they had there engine.
Now you should be able to transition from idle to high with no hesitation. Make sure you are a hundred or two rich on the top end and you have good baffling.
Now fly a couple of gallons thru the engine and then do your final tweaking by how it responds in the air.

DKjens

My Feedback: (50)

Brian,
These gas engines will often not act very linear with the amount of throttle given. It is different from engine to engine and from engine/airplane/prop/exhaust combination to combination. If your engine doesn't seem to increawe very much in power from 1/2 to 1/1 throttle, it may just be your combination. I most often use a throttle curve for my engines (150cc and up), where 1/2 on the stick yelds 1/3 throttle opening. As you said, you very rarely use 1/1 throttle, so broadening the area you do use on your stick makes flying much nicer.

DKjens

RTK

My Feedback: (1)

Very good point DK, I did not even think of that. I just ass/u/me everyone mechanically sets it up this way and then fine tunes with a curve, but you should still see something from 1/2 to full throttle.