BME 50cc acting funny
05-26-2005, 12:48 AM
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BME 50cc acting funny
I asked for help in the engine forum and did not receive much help so I thought i would ask here since it is in a giant scale plane. I have a Aeroworks 29% Edge with a 50 cc BME engine on it. Engine runs fine on the ground and in the air except when I get wild with it. Say I do a double snap roll or a flat spin, the engine rpm's drop to a idle for about 10 seconds. I replaced fuel lines, cleaned filters, rebuilt carb, and installed a new spark plug. Engine still does it. Can someone give me some pointers please. Any help would be greatly appreciated.
Jeff
Jeff
05-26-2005, 06:57 AM
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RE: BME 50cc acting funny
blue ice
Give us some more info, such as type of radio equipment etc. Some RX's will drop to idle if the battery voltage goes below a certain point. It could be some sort of failsafe as well.
Another thing you might try is to use a felt clunk. Sometimes a violent manuever could cause air to enter the fuel line. The felt clunk will prevent this.
10 second idle is a looong time after something like a spin. Hopefully you have some spare altitude when this happens.
Safe Flying!
Give us some more info, such as type of radio equipment etc. Some RX's will drop to idle if the battery voltage goes below a certain point. It could be some sort of failsafe as well.
Another thing you might try is to use a felt clunk. Sometimes a violent manuever could cause air to enter the fuel line. The felt clunk will prevent this.
10 second idle is a looong time after something like a spin. Hopefully you have some spare altitude when this happens.
Safe Flying!
05-26-2005, 08:46 AM
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RE: BME 50cc acting funny
Could be a lot of things. I had that same combo and the cowl is real close to the carb inlet. Is the cowl moving around and choking the engine? Is the choke lever being moved aound by the cowl? Did you cut a hole in the cowl for air to get to the carb? I didn't. The Carb is mounted on a plastic manifold, is that cracked or loose? Post a picture of the carb area with the cowl on and off if possible.
05-26-2005, 10:00 AM
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RE: BME 50cc acting funny
Sounds like a fuel pick up issue. Check that the fuel pick up in the tank is staying at the back of the tank, and not being bent or doubled up going to the front of the tank. Possibly a vent line getting pinched off in violent maneuvers. Unless you want to clean the filter scrfeen in the carb all the time, don't use a fely clunk. They often create more issues than they cure.
05-26-2005, 11:22 AM
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RE: BME 50cc acting funny
I installed all new lines in tank so I dont think that is the problem. As far as radio goes I am using a 8 channel pcm rx(futaba) with a 9c tx. I have never done anything with the f/s programing but just looked and everything is set to 0 except for the throttle which is set at 20%. If it went into f/s mode would I still be able to control all the other surfaces? I do have control of plane while the engine is at idle? I bought this plane used and the gentleman who sold it to me said he never had a problem. Looking at BME's website, they sell a new design cover fr the carb that has a nipple on it. Might I be smart to make one of these and give that a try?
05-26-2005, 11:42 AM
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RE: BME 50cc acting funny
What batteries are you using? Lots of current draw on a poor too little battery can cause huge voltage drops.
PCM Futaba has 2 options of fail safe. One is when you get interference, as you described above. You have no control of the plane but you determine where you want each and every servo in your plane.
The other is when your battery voltage goes below a certain voltage (around 3.8 volts I think). When this happens, throttle goes to iddle as long as you do not put your throttle stick to iddle to "reset" the thing. This is to give you some time to land while still having enough battery power. This functione, to the best of my knowledge, is not adjustable.
I suspect your batteries do not provide the juice.
PCM Futaba has 2 options of fail safe. One is when you get interference, as you described above. You have no control of the plane but you determine where you want each and every servo in your plane.
The other is when your battery voltage goes below a certain voltage (around 3.8 volts I think). When this happens, throttle goes to iddle as long as you do not put your throttle stick to iddle to "reset" the thing. This is to give you some time to land while still having enough battery power. This functione, to the best of my knowledge, is not adjustable.
I suspect your batteries do not provide the juice.
05-26-2005, 09:15 PM
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RE: BME 50cc acting funny
If the battery failsafe is realized you have to return the throttle stick to idle momentarily to regain throttle control. This should help identify this specific phenomenon.
The carb part pictured is a good idea in any event IMO. This device allows the fuel metering diaphragm to work with undisturbed or consistent air pressure. In practice as your banging around in the air the air pressure within the cowl is ever-changing. This effects the fuel metering diaphragm as it reacts to these pressure changes.
With BME's gadget you route a fuel line to an area inside the fuse or better yet IMO to the carb throat opening. The latter allows the metering diaphragm to realize the same pressure as the carb air inlet. It’s all good.
The carb part pictured is a good idea in any event IMO. This device allows the fuel metering diaphragm to work with undisturbed or consistent air pressure. In practice as your banging around in the air the air pressure within the cowl is ever-changing. This effects the fuel metering diaphragm as it reacts to these pressure changes.
With BME's gadget you route a fuel line to an area inside the fuse or better yet IMO to the carb throat opening. The latter allows the metering diaphragm to realize the same pressure as the carb air inlet. It’s all good.
05-26-2005, 11:37 PM
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RE: BME 50cc acting funny
Thanks for the advice guys. I called Desert Aircraft and asked them what they thought and the tech I talked to agreed with you 3D Joy. I have a new pack on Charge now and will try it again this weekend weather permiting. I hope that is all it is.
05-27-2005, 10:59 AM
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RE: BME 50cc acting funny
Even if it turns out to be a battery issue the diaphragm static balance tube is a good idea for the reasons that Michael stated. It will go a long way toward eliminating those heart stopping stutters that often occur after violent manuevers.
ORIGINAL: mglavin
If the battery failsafe is realized you have to return the throttle stick to idle momentarily to regain throttle control. This should help identify this specific phenomenon.
The carb part pictured is a good idea in any event IMO. This device allows the fuel metering diaphragm to work with undisturbed or consistent air pressure. In practice as your banging around in the air the air pressure within the cowl is ever-changing. This effects the fuel metering diaphragm as it reacts to these pressure changes.
With BME's gadget you route a fuel line to an area inside the fuse or better yet IMO to the carb throat opening. The latter allows the metering diaphragm to realize the same pressure as the carb air inlet. It’s all good.
If the battery failsafe is realized you have to return the throttle stick to idle momentarily to regain throttle control. This should help identify this specific phenomenon.
The carb part pictured is a good idea in any event IMO. This device allows the fuel metering diaphragm to work with undisturbed or consistent air pressure. In practice as your banging around in the air the air pressure within the cowl is ever-changing. This effects the fuel metering diaphragm as it reacts to these pressure changes.
With BME's gadget you route a fuel line to an area inside the fuse or better yet IMO to the carb throat opening. The latter allows the metering diaphragm to realize the same pressure as the carb air inlet. It’s all good.
