BME owners and public in general:

What do you think about this spark plug ?

Too lean?

Lean is a light grey or almost a tan to white color. That does not look very light from that picture. A light brown is what looks good from my experience. That doesn't look too bad.

Looks pretty good, what are your engine temps right after landing?

Thanks Joe

The engine hesitates during the take off, then couple of seconds later seems to run fine.

I am seeing oil traces underneath the fuselage, then I guessed it should be still bit reach, then decided to leaned the low needle, just little bit, however next take of did same thing, engine hesitated. I tried to open the throttle gently.

I am getting 6300 on the ground, I guess should be OK.

1) The oil traces might be explained since the oil/gas rate I am using 40:1. I am using Motul 800 synthetic. The guy at the Honda bike dealer told me that is one of the best they carry for motocross and 2 stroke competition engines. They don't carry AMSOIL in Mexico.

2) I think is too soon to for this engine to use less oil, however the only thing that puzzles me is that weird behavior during take off. Sounds like its got way too much fuel at this point, however I would like to ask before leaning more the needles.

flyingrazback

After landing this is what the flying data recorder showed, 230 & 175

This is the plot of the engine temperatures:

It looks a little rich on the high end ,but not excessively .
The spattering on the plug looks like maybe too much oil in mix , what oil and ratio are you using and what octane fuel and how old is it?

Albatross- There is a fine line on the 110 between perfect on the high and too lean. If you are a little rich on the high it can cause the upper mid range stumble.

If you let your engine idle for 20 or so seconds (on the ground while restrained) and goose it does it stumble? If it does not stumble while motion less on the ground, you will have to look at other causes.

Wish I could get my temps that low, but I haven't finished my baffling work yet. By the way how hard were you pushing it in that chart above?

RTK

I see what you mean, the needles of this engine are very sensitive.

Stumbles on the ground. However typically after hand starting the engine just before the flying session, when testing the engine on the ground:

From idle goose, stumbles then finally reaches 6300, 6200.
Throttle back. let the engine idling, wait some time (no sure how ), goose then the transition is just fine this time.

Taxing, then open the throttle, exactly when is gaining altitude or before the engine stumbles.

I am getting used to this stumble, however is pretty scary. I don' think is right.

By the way, I am positive I am working my way to the lean area since the two maiden sorties I did I noticed some smoke coming along, at that point I started leaning the needles. It has been 4 weekends so far after that maiden. 3 flights each weekend only 7-8 mins long. Before that I ran the engine on the ground on a test stand at no more than 4000 rpm, reach 2-3 gals on ash less oil.

Between the 5 and 7 mins mark of that plot I am sure corresponds to the time I was torque rolling the airplane.

The oil I am using is Motul 800 40:1, if I am not mistaken, the Octane of this gas is 87.

The oil traces in the LG and fuselage might indicate that I might be in the reach end. should I try 50:1?
However the spark plug indication is saying that I might be Ok , as you said it is not excessively reach.

On mine I am having the same or similar challenge getting the needles just right. Initially I could advance the throttle quickly to mid stick and it would go, from Idle to full or mid stick to full there was a lag after prolonged idle. I wouldnt call it a stumble but it didnt take throttle. So I have the low speed to a point where I think its lean enough, then started working the high speed lean in 1/16 turn increment and seeing improvement in throttle response.

But my initial behavior was similar to yours, that is its fine in the pits but on the take off roll it didnt take throttle for a good part of the takeoff roll but finally goes. I also see the oil spots on the bottom of the plane, Im at 32:1 pennzoil.

Where are your temp probes located?

Just a side note for anyone, once a plug is established as rich, that is its dark, when you get the needle set lean does it go ahead and lighten up?

Brian

I read that plug as being the correct mixture with high oil content

Thermal sensor location:

I have not tried to lean the engine any further to check what color the spark plug does it turn yet.
Even with the baffling I installed, I am afraid about reaching any point of not return and ruin the engine. I understand that takes more than one flight to "paint" the spark-plug. I may try that later.

[quote]ORIGINAL: Geistware

I read that plug as being the correct mixture with high oil content
Thanks Geistware, I guess that matches couple of opinions so far.
MOTUL 800 is seems to be the best oil I can find around here and as far as I know BME 110 likes low octane gas, which is what I am using.

Look here for plug readings [link]http://www.prme.nl/forum/viewtopic.php?t=10[/link]

Specs on the fuselage is not a mixture indicator. Look down into the plug where isolator meets plug body. If you see a black ring, the mixture is OK.
The black plug body is indicating a slightly rich mixture. Oil has little to do with that.

Placing the sensor on the front of the engine gives low temperatures. The prop turbulence forces the cool air deep into the finning. They should be placed at the rear, where the sensor is not cooled by the airflow. That is the main reason for the massive temperature rise after stopping the engine.

That's a good point, the air flow will give you lower temperatures.

After using the Hand held IR thermometer and the thermocouple sensors, another conclusion is that is very hard to say what is exactly the engine temperatures. I think depends, where you are measuring the temperatures, what are you using and when you are measuring them.

Thanks for the link to plug reading.

The plug looks real good. Don't touch anything.

Thanks guys, really useful information. I am glad I am member of this forum.
Few I mean really few of us are flying twins around here, so I have little feedback and help.
Counting on your opinion is crucial.

Merry Christmas !

The plug itself was showing a pretty good mixture setting. You can mix the Motul at ratios of 70-1 to reduce the soft carbon build up on the plug. What I see here is consistent with a 50-1 Belray mix on plugs with 100 plus hours on them so overall it's good.

The reason for the "stumble" is because the engine is still cold. You stated that after it idles for a bit all is well, so that was a key statement. Moving the thermocouple to the back of the engine but in the same relative location on the fin will give a more accurate heat reading.

Pat

I would attach the thermocouple to the spark plug washer.

That would indeed be the best, and standard solution. With the tie-on thermocouples like the Venom etc, that is not an option.

If that is a new motor, perhaps you should try the non-synthetic oils first for mabay a couple of gallons and then go to the synthetics. This will seat the rings quicker and give you more power and more consistent running engine. If you try adjusting the fuel rich and lean both ways and it still hesitates on take off, make sure all of your seals around your carb is good and nothing has loosened up. If not the case, check the inlet nipples that attach to the fuel lines to make sure they havent lossened up as well. If you do all that and it still is hesitating on throttling up, call BME and tell them you may need to send the engine in to them! BETTER SAFE THAN SORRY...... I am not sure were else to take it,,,, I have spent over 10hours straight trying to get an engine to run right and then I found it had a faulty ignition when I sent it in for warranty..... Oh, one other thing ... Try changing the spark plug for new one and then see if it still stumbles.....
Hope I have helped.

As mentioned earlier make sure the engine is warmed up, especially before changing any needle settings.
Does it ever hesitate/stumble in flight when you go from an extended low throttle setting to high throttle setting?

Regarding the thermocouple position. A pretty accurate reading will be obtained if you move the thermocouple to the back of the cylinder, second fin down from the top. You can use the cylinder screw access holes to clamp the wire in place by running a short hex head screw and bolt into the hole, and using a couple of flat washers as clamps on both side of a fin. This has been done on about a thousand engines that I'm aware of and it works just great.

If you have the ability, attaching at the base of the spark plug is the best, but as noted before, not always possible.

SS- I think he is using a thermo-couple that wraps around the cylinder so to speak with no need to mount it. But you are right, the rear of the cylinder (in relation to air flow) tends to be hotter. Especially if you do not use much baffling as I used too.