TimT2000

My Feedback: (1)

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I had a dead stick in a hover with my BME 102 in a 75cc AW QB 260.
Bent the gear but now have carbon ones on the plane. The engine just quit.
First engine out I have ever had with a gasser, some suggested the ignition
may have over heated as it is under the engine box behind the mufflers.
It sparks now and I can find nothing wrong with the setup. The pics were
taken after the engine out, they are one and a half years old and have about
4 gals. of gas through them. I am using TCW-3 outboard oil in all my gassers
and so far all the engines are clean. 40 to 1 ratio.
TIA

Tim

w8ye

My Feedback: (16)

You should be using aircooled oil and not marine oil.

But that is not why your engine quit.

Those plugs look a little on the lean side? One is a little more lean than the other.

TimT2000

My Feedback: (1)

Yup, not the oil most people use but I have a ton of it and cheaped out

The plugs look lean to me also, I was shocked to see them as I thought it was
plenty rich on the big end. But it is not looking that way.

The engine did not sag and had great response right up until it quit like it was shut off.

Now I don't trust it. I am relocating the ignition inside the engine box. Or is this silly.
Tim

Tired Old Man

My Feedback: (1)

From what I could discern the plugs indicated things are a bit lean. The engine may have just got hot and stopped. BME's don't always fade out like most other engines, mine has stopped as abrubptly when it was running lean and hot. Moving the ignition away from the exhaust is a very good plan.

TimT2000

My Feedback: (1)

TOM thanks for the info, I better rethink my tuning's. I pride my self for smooth running gassers
with no burble, 4 stroking or break up in the mid range but it looks like I am running them lean.
I will open the high needle 1/4 turn and maybe lean the low end a little for starters. I bet it will start burlbling a
little in the mid range but that is better than burning them up and having a engine out!!. I hear the Masters
planes running rough in the mids, but I may be the one that has mis tuned.

I bet Jedi Jody is going to punch me for the oil I use and running so lean.

Tim

MetallicaJunkie

lean....mine are usually a couple of shades darker...and look oily whenever i remove them ...i had an engine that i tuned for max rpm(dumb*** me [:@])....ran great i did 2 wot flybys, and after that it was bogging...i had to cut down to 1/4 throttle so it wouldnt quit ... i landed and and the plug looked pretty much like yurs i ritchened the highe end a couple of hairs and it ran great...

TimT2000

My Feedback: (1)

so should I start setting the high end 100rpm rich from max or so like we do the slimers (glow) engines?
I thought I had it right ,, but you know I might have set it up on a hotter day where I needed to lean it a little
to make up for the lack of oxygen. At the WOTR my engines ran fine at 1 mile high so I thought the walbro
had seen this. This might not be true for temp. changes.
Thoughts?

Tim

MetallicaJunkie

as long as you keep your fuel mix consistent... i would say 100 is acceptable ... i tune with the engine on, i adapt a socket head screw on my highend so the driver stays put.. i rev to WOT and and lean out high end till i hear a slight drop in rpm, then richen it till it peaks again, then richen it a hair more than 1/8th of a turn

av8tor1977

My Feedback: (6)

They look lean to me. It is sometimes hard to tell with the fuel we have today, but definitely lean by the looks of them...

AV8TOR

Tired Old Man

My Feedback: (1)

A Walbro will self compensate with an altitude delta of about 6,000' from what it was originally set at, so the carb itself is a non issue. The temperature delta would need to be >35 degrees for re-tuning to provide much benefit if things were right to begin with. Plain and simple, the high needle is a little tight. If the low needle was also set lean enough that the engine throttled up and down without hesitation when the engine was cold it would be overall too lean. Throttle response should not be good until after the engine warms up.

There's no need to tune rich of peak. In fact, when engine cooling is done right you'll get the best performance lean of peak, but you need to do the cooling side right. So if it was mine I'd go back to the needles, starting with a warm engine not a cold one, and do some fine alignment work. It might be easier to start at square one with the needles set at 1 1/2 and start over. If that could all be done with the plane safey restrained and the engine running continuously, so much the better. But you are the one that will be determining what is safe or not safe for you to do.

jedijody

My Feedback: (1)

I wouldn't punch you, besides, it doesn't look like you'd need it, looks like you're taking good advice very well.

If your cooling is done well you shouldn't need to richen the high below peak RPM, you want the high needle right at the rich edge of peak but not rich enough to drop any RPM.


For Pete's sake TOM, you beat me by 2 minutes.

rc bugman

My Feedback: (30)

Hi,

The only problem with using TCW-3 oil in an airplane engine from my experience, is that the exhaust residue will harden and clog the small holes in the muffler during the winter when the engine is not run on a regular basis. Otherwise, the oil works as well as air cooled or in some cases better at keeping things clean. All of my experience was with Pennzoil marine synthetic oil. Other oils may be different.

Elson

soarrich

My Feedback: (98)

@ TimT2000

Do you baffle your engine?

The other day I saw a Yak with a nice 3W sitting there in the cowl not baffled. I mentioned it should be baffled the response was, "It gets lots of air."

Ih82crash

A quarter turn is too much. Gas engines are more sensitive than glow engines. I would start with a 1/16 of a turn rich.

jaka

Hi!
Do not richen the high speed needle! It's not a too lean setting that is the culprit. The problem is probably no baffles! The engine gets too hot due to the air is not passing trough the cylinder fins!

Tired Old Man

My Feedback: (1)

Oh, it's definately running hot. Cooling air is part of it, as is mixture. Something few consider is what they were doing before going into a hover. Was it a bunch of torque rolls, harrier flight, knife edge spins, and tumbles? If so the engine was already hot, regardless of baffling, and the hover finished it off.

TimT2000

My Feedback: (1)

Well I hate to say it but no. I have a 102cc stuffed in to the 75cc plane and the cowl is pretty full. Tell me what you
think.
Tim

TimT2000

My Feedback: (1)

I got her back together for a flyin in Columbia, MO. today, moved the ignition in side the box, loaded up 4 planes and took off. I did richen up the high side an 1/8 turn, no WOT burble. So I went 1/4 more and had a slight burble at WOT. So back lean 1/16 and perfect, clean at WOT and sure it is at the richest setting with out stuttering. Flew it four flights
and it ran just great, super power and a slow smooth idle. Midrange was just fine. Now what? should I baffle the cowl?

Tim

TimT2000

My Feedback: (1)

I think you called it like it was, please see pics and suggest how to baffle this cowl. Notice the cracked paint on the
bottom of the cowl, it is not perfect anymore so now I can fly it harder right?

Tim

soarrich

My Feedback: (98)

The air is going to take the easiest way through the cowl, so I bet most the air that goes through the cowl will go down in front of the cylinders. It looks like it would be very easy to put ducting straight back from the lower edge of your cowl opening, make it with the engine shape cut out looking down on it, the trim the outside edge to fit in the cowl. I use foam-board from the craft store, it's about $3 for a 20"x30".
From the front your cowl air exit looks more like a air scoop to me. [X(] I think you need a spoiler at the front of it to help make it a low pressure area. This guy has a really good page on cowling and ducting, (but it's down right now, anyone know a better link?), http://www.supercoolprops.com/

TimT2000

My Feedback: (1)

Yes it does. With the mufflers on it, it fills up that area pretty good just inside the cowl and has the pipes sticking
straight down. I run smoke on this plane quite often, can this heat up an engine with added back pressure?

I am going to work on a baffle for the BME but I have no idea what to do with the big hole in the bottom. A nice spoiler
on the bottom could look pretty cool.

Any pics of one that works?

Tim

soarrich

My Feedback: (98)

Here's a few shots of my baffles, I don't try for perfection, I just try to get most of the air that comes into the cowl to go through the engine's fins.
I don't know if I have any pictures of spoilers, I try to put my outlets in low pressure areas. I'll see if any of my planes have spoilers on them and take some pictures if I do.

Tired Old Man

My Feedback: (1)

Use the big hole on the bottom to your advantage. Make a low pressure generating lip. Add a ramp inside the cowl, behind and under the engine that forces air to follow it out of the ramp.

TimT2000

My Feedback: (1)

Thanks Soarrich! I went flying at our field in Eldon, MO. today and talked to a new friend like you all that have been there.

I took some pics of setups so I could find a place to start. This guy has his DA 150 set up with heat shields for the
carb. and an outlet duct like you are talking about. Looks like I have work to do!

Tim

TimT2000

My Feedback: (1)

Good info, TOM I noticed my high screw is not as touchy as many have said. I did open the screw just a hair over a 1/4 turn to get the high end rich but with no stutter. It is smooth and powerful now. Do you see this as some clue or was I just really lean.

Tim