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evo 58 gx losing power

Old 01-29-2008, 09:23 PM
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at7driver
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Default evo 58 gx losing power

Hi all,

I have an evolution 58gx that started losing rpm's... I flew it yesterday and all was well. after about 30 minutes on the ground started right up and after a short warm up period, about 1 minute I advanced the throttle to check the transition and tach it.. I only had about 5600rpm (24x10, woodie prop), then it quickly started losing rpm's... to the point where I decided to shut her off. A friend with the same engine mentioned his carb block had come loose and he had a similar situation. any ideas ???? Haven't had time tonite to take the cowl off etc.. thought I would post on here then go check it out...

thanks in advance,

david
Old 01-30-2008, 02:25 AM
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Default RE: evo 58 gx losing power

Hi,

please check your battery for ignition.
Old 01-30-2008, 09:42 AM
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Default RE: evo 58 gx losing power


ORIGINAL: at7driver

Hi all,

I have an evolution 58gx that started losing rpm's... I flew it yesterday and all was well. after about 30 minutes on the ground started right up and after a short warm up period, about 1 minute I advanced the throttle to check the transition and tach it.. I only had about 5600rpm (24x10, woodie prop), then it quickly started losing rpm's... to the point where I decided to shut her off. A friend with the same engine mentioned his carb block had come loose and he had a similar situation. any ideas ???? Haven't had time tonite to take the cowl off etc.. thought I would post on here then go check it out...

thanks in advance,

david
Loosing rpm is a problem symptom than can be anything from overheating to fuel starvation to loosing sparks to engine mechanical condition and blown seals. You must be a bit more specific, so I suggest you do the obvious things first, like preliminary checks with the cowl off, internal carb fuel filter, sound tank pipe lines that do not leak fuel or air, sound gaskets etc.
Is the throttle hooked up well and responsive to servo throws? Does the servo move like commanded by the transmitter?
Old 01-30-2008, 12:59 PM
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at7driver
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Default RE: evo 58 gx losing power

Hi guys,

After checking the engine over.. the ign batt is good, good spark, good throttle servo, good fuel lines, no fuel leaks. I will check the internal carb filter screen tonite. also will check the mounting block where the carb is attached for tightness.

I dont suspect lean fuel settings as I had just flown it twice before with great performance.


thank you for the help


david
Old 01-30-2008, 02:39 PM
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pe reivers
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Default RE: evo 58 gx losing power

I suspect mixture leaning out due to clogged internal carb fuel filter.
You did have an open tank vent, did you?
Old 01-30-2008, 11:01 PM
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at7driver
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Default RE: evo 58 gx losing power

Hi,

Yes there is a tank vent to atmosphere.. just got in from work and heading to bed.. will take the carb apart tomorrow to check the screen.. what type of inline fuel filter do you recommend.

thank you,

david
Old 01-31-2008, 08:07 AM
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pe reivers
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Default RE: evo 58 gx losing power

I use a felt clunk in the pickup line, which has NO T, but is a single line directly to the carb.
The felt is well kneaded and rinsed in clean gas before installing.
Old 02-03-2008, 03:10 PM
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at7driver
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Default RE: evo 58 gx losing power

Hi all,

finally had some time today to clean up the screen.

It wasn't bad, a light coating of crud in a very small area. I installed new fuel lines as well.

I ran it on the ground, still had the same problem at full throttle she seems to lean out, rpm loss. If I only advance the stick about halfway she will run great, tachs out at 6750 (24x10 tbm wood prop)... if I advance the stick to full throttle she leans out and loses rpms... my first thought was that somehow the throttle linkage got messed up but it seems fine. I have not changed any programming on the tx that would affect the throttle end points.

so do you think it possible that there is a restriction at full throttle that is leaning it out. I thought about just re-setting the throttle servo so that half stick is now full throttle but wonder why it was working fine one flight then the next flight (30 minutes later) it wasnt..

any ideas,

thank you,

david
Old 02-03-2008, 06:03 PM
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pe reivers
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Default RE: evo 58 gx losing power

What does the plug look like. Is the carb pumping OK? Crankcase line to carb OK? Fuel passage inside the carb to main regulating needle OK? Fulcrum height with regulating needle low or high? It should be even with the surrounding carb floor when the needle just opens.
6750 on a 24x10 prop is not bad at all and indicates a healthy engine, but she should run well at full throttle.
Old 02-03-2008, 10:57 PM
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at7driver
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Default RE: evo 58 gx losing power

hi,

It appears that when the tx stick is "full" throttle the carb plate is open past the 90 degree point, in other words it is over center, partially closing the bore. I don't have an explanation as to why it is doing this now, I have checked the servo, linkage and all appears well. I guess it is possible that the arm slipped on the carb somehow. I have her on the stand and will check into it further before the upcoming weekend.

I could see a situation where the carb plate goes over center, thereby reducing the airflow into the carb or perhaps "choking" the engine to a degree, does this seem plausible?? I am guessing the plate position for full throttle to be 90 degrees from closed.

I pulled thru 4 blades, then two flips with choke on she fired, and two more with choke off and she fired right up, as usual.


thank you again for your help.


david
Old 02-04-2008, 08:42 AM
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pe reivers
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Default RE: evo 58 gx losing power

you can set the tx/rx adjustments, so that the plate does not quite reach full throttle position, but stays just shy of it. That will give you the best throttle response as well.
Old 02-04-2008, 04:29 PM
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at7driver
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Default RE: evo 58 gx losing power

Thank you,

I will make the adjustments after I go thru the linkage again just to make sure nothing is loose.


Thank you again for your help,

great engine, pulls my lanier yak around very well.


david

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