krayzc-RCU

My Feedback: (31)

I picked up a new carb for my BME 100 because it use to hang for a long time in the high idle. Today I put the carb on there and still no improvement with the high idle. Once the motor has run about 20 seconds all of sudden the idle will go down 300-500 RPM. Upon starting the motor I am noticing there is a slight kick back in the prop while starting. I am not tring to get a prop bite. Can anyone point me in what may be causing this wild type of idle along with the kicking back that I am starting to feel. I don't know how the timing is controled I would guess its locked into the C & H box.

Thanks N advance...

Geistware

My Feedback: (16)

The high idle thing is a part of the engine. All the ones I have seen do it and mine does it as well. As far as the kick back, I would say that is a problem and it would be in the ignition unit.

TLH101

My Feedback: (90)

If it has a C&H Synchro Spark, could be the ignition is not retarting as it should be. Nay be the reason for both problems. You should call the guys at C&H and have a talk with them. They should be able to halp if it is an ignition problem. Easy poeple to deal with, and really helpful.
You can find the number here: http://www.ch-ignitions.com/

Geistware

My Feedback: (16)

Terry,
I sent my ignition in because one coil went bad. They replaced both and the wires and it still would not slow down until the plane was almost stalled.

Tim_Indy

A low speed needle setting that is too lean will also cause the idle symptoms you describe in any 2 stroke engine, be it glow or gas. In this case, richen the low speed needle in 1/16th turn steps until you get a stable idle that doesn't change. It won't take much, as the low speed needle is sensitive to change. You probably will have to use your transmitter trim to open the low throttle a bit, but your engine will not only idle better, it will run cooler at part throttle settings.

Regarding kick back, it definitely could be a faulty ignition, but I've owned the BME 102, the 105, and now have a pair of the 110 Beemers, and the only time they have ever kicked was when I tried to start them and they were flooded (any engine will kick back in that case). You probably already know this, but that's the reason my starting procedure is to close the choke and turn the ignition ON, then flip the prop about 4 times until it "pops" or tries to start. It now has just enough gas in the cylinder to run so I open the choke and within 3 flips, the engine is running. Many guys choke their engine with the ignition off. That may allow too much fuel into the cylinder, flooding the engine and inviting kickback. My way lets the engine tell me when it has just enough fuel to start.

Geistware

My Feedback: (16)

Tim,
What I find on my engine is that when I come in to land, the idle is high until just before the plane is at stalling speed then the idle goes down to the speed set on the ground. In my case the engine is not lean, it just idles fast until the speed drops down. What I have been told and what seems to work (but I seldom use it) is to set an idle down speed that is lower than normal idle. I did this along with some reflex in my ailerons and elevator and the engine will idle extremely low when hot but when first started, it will die if I activite the idle down feature.

Albatross

My Feedback: (7)

When I tested my BME 110 on the bench, I had a similar experience. I suspected I had a timing issue with this engine as well (see the link to the thread I sumitted in regards to timing concern). BTW those kick backs really hurt. I did not feel any pain on my hand, somehow the impact was received by my elbow tendons.
Tim remarks a good point, he describes the right way to start this engine.

[link=http://www.rcuniverse.com/forum/m_2956646/anchors_2956646/mpage_1/key_BME%252C110/anchor/tm.htm#2956646]BME Timing[/link]

krayzc-RCU

My Feedback: (31)

thanks all for the tips I have not made any adjustments on the new carb when i tried to adjust the old carb I could take the low out to about 4-5 turns and the engine still did that high idle. I did make any adjustments on the low or high i just started with the 1 /14 and 1 1/2 settings. After I felt the kick back i did not want to flip that baby anymore. I have never been bite and really don't want to lose my virginity in that area I will see if the new carb does effect the low end I am on it now. I should be back in a few hours it not that may not be a good sign[>:]

Geistware

My Feedback: (16)

Waiting to hear your reply.

krayzc-RCU

My Feedback: (31)

Okay the night set in on me but this is what I accomplished:

By turning, the low out to 2.5 this would drop the idle to 1800 within 5 seconds 20 seconds later the motor would drop to 1100-1200 or cut off

By turning the low back to the factory setting 1.25 the idle would hold at 1800 then creep down to 1650-1700

The high is about one or 1 1/4 getting 6300 on a 26 x 10 Menz

The transition is better with the needle set at 1.25 right now almost instance throttle response.

With the low out, over two the idle was better but the clean up was not right away about 5-8 seconds to clean up.

one the last cut off before the night set in I moved the low end in to 1 or 1/18 then the kick back was there so I let the motor cool off to see if i would get one more in before the vampires come out. It was like the carb got flooded just sitting.

When I first tried to start the motor I tried the flip it six times with the choke on ignition off then turn on the power and the motor started on the second flip cool!

I have a brison 3.2 and 3W-150 and they all idle lower than this baby will run right now. It is shaky idle until it cuts off on the 1100-1250 area if it runs that long. The motor will get this low idle when or if it make those drops out of no were. I would think I should be it 1400 RPM idle like it's cool.

At 1800 RPM, you have one fast taxi bird. What idle are you all getting? I can start all of my other gassers and they would not run after you. What are the symptoms of needing rings since this is an older motor? I would imagine loss of compression or low power (hum) [X(]

I will be back at it on Saturday to see what I find out with the low end. I am hoping i can get a clean drop to 1400-1500 RPM

??????

RTK

My Feedback: (1)

I would say that Tim is correct, but since it did not work for you, I can only think of two other reasons. #1 possible defective ignition (they had a few), #2 space between the carb and cowl to small, if so, cut a hole below the carb.

krayzc-RCU

My Feedback: (31)

Hum space between the carb here are some pic were I built some f-glass around were the carb is sitting so it not out in the air.

Was that a no no there is about 1 inch of free space at the bottom

RTK

My Feedback: (1)

1" should be enough, But I had a little less on my comp-arf with a BME110 and it exhibited the same symptoms until I cut a little hole below the carb.
It would idle down very slowly, it also accelerated slowly (not rich) just seemed constipated. Cowl off everything was fine.

I still think the ignition might have something to do with it if all else has failed. Does it run fine with the cowl off??

Nice work on the cowl by the way.

Geistware

My Feedback: (16)

I wanted to comment on these two areas of your post.
I don't know what my high end needle setting is but my rpm at WOT is about 5900 using the same propeller you are using. I know I am running rich.

I use the same first start procedure you use but with 7 flips and my engine starts the first time 90% of the time. I choke the engine off so that no choke is needed for re-starts.

THe last thing, how is your airflow around your diaphram? I have found that the engine is very sensitive to pressure or airflow changes around the diaphram pump. I used a 3W intake manifold and it made my idle very consistant without any changes. (on the ground)

Duing landings, I still get the auto idle down as my planes airspeed drops off prior to touchdown.

Crusty

Krazy, the carb shroud is not ideeal, it is probably creating a low pressure area at its open face, it would be better suited as an air exhaust

krayzc-RCU

My Feedback: (31)

Crusty

R u saying I need to cut an air hole in the bottom of the cowl?

Geistware
i would suggest to go in some on that high end so that you can get some more RPM. Even with the factory setting on my motor I still go 6050 on the RPM.

BBW Walt

My Feedback: (11)

Hey Krayzc: I had a BME 100 on an Aeroworks SU 31 which did some of the nonsence your describing. Mine kicked back once and sheared off the 6/32 hub bolts in the prop driver. But the idle thing was always there with this engine. I just went with long drawn out approaches while landing. I eventually sold the plane and along with it I threw in a Mejzlik 26-10. The new owner put the Mejzlik prop on the exact same set up and the motor instantly became happier. I attributed this change because the Mejzlic was a heavier prop than the Menz 26-10 I was running and it just seemed to settle in better coming back to an idle. In my head it seemed like a flywheel effect or like the extra load from weight of prop made a difference. RPM came up on hi end also. I always run Menz props but the Mejzlik made the difference on this one and your situation sounds pretty familiar with the one I had, hope this helps, Walt

Geistware

My Feedback: (16)

Thanks Walt.
I may try a Mejzlik.

Krayzc,
I will go in 1/8 turn on the high end and put some stick time in.

krayzc-RCU

My Feedback: (31)

i will get me a mejzlik on order right now i will also so somemore testing tomorrow (Sat 9/3). this baby is going to get figured out u can best believe that one!

Geistware

My Feedback: (16)

DA doesn't have any.
I just checked.
If you find two, let me know.

krayzc-RCU

My Feedback: (31)

http://www.hobby-warehouse.com/2blcafipr.html

http://www.skylarkrc.co.uk/Mejzlik.htm

i ended up getting one from one of these 2 places as DA was out.

I did it all on line so i am not sure they even have it at this point..

mglavin

My Feedback: (31)

Krazy what’s the carb p/n#? New and old same thing?

Why are you choking with ignition off and then flipping the engine? I think this is unsafe choke and flip with ignition on, the engine will sputter and die when enough fuel is present to fire rather than load up and flood with ignition OFF.

Tim mentioned the best method to diagnose your dilemma IMO.

Some of these carbs high speed needle affects low end operation. You might experiment here too.

Did you remove the cover plate to install a vent line tube barb or similar?

Geistware

My Feedback: (16)

Michael, this is not true.
I have had over 500 flights on my BME102 and this is how I have started it on the first flight for the entire 15 months that I have had the engine. I will admit it is unorthodox, it does work very well.

RTK

My Feedback: (1)

Geistware, to each his own, but I find no logical reason too not have the ignition on when choking.

mglavin

My Feedback: (31)

I understand it works, BUT why take the risk? You're simply asking to get bit IMO. You don't know if or when the engine is adequately primed or flooded. So why go there? It's not like there is any reason to NOT do as I others suggest? What does the BME manual suggest?