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Can't get 58DC to run right...

Old 12-08-2007, 12:39 PM
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*JCB*
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Default Can't get 58DC to run right...

I have a newish 58CD that just doesn't run right. It seems that mid-high range runs great and smooth, but the motor WILL NOT drop below about 4000 rpm reliably. It will hit about 3800 rpm, start running VERY rough and just conk out. I am running powermaster 15% sport fuel, an OS type F plug and a 12x6 prop. I have tried reseting the needle valves (per manual) over and over and over, i've tried new plugs, fresh fuel and many different needle settings in both directions and it just runs the same.

Also, this motor doesn't really respond to high speed needle settings very well. It seems as if it needs a drastic change to change RPM in either direction. The motor seems to be running rich as there is oil spray all over the ground...

The motor has about 90 minutes total run time on it as of now


I don't get it!! Please help!
Old 12-08-2007, 01:48 PM
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Default RE: Can't get 58DC to run right...

When the motor is running rough at low speed, what happens if you pinch the fuel line?
Does the motor smooth out and speed up, or just drop revs immediately.

The factory needle settings are for a rich run, safety settings if you like.
The idle is critical, and I have found the only reliable way to set it is with the motor running. Set it the same as you would the high end.

90 minutes is not much run in time for an RCV. I would always put about 4 to 5 20oz tanks through before removing it from the engine test stand.
Even then it will change in the first 5 to 10 hours use.

But it does sound like the idle needle is playing up, have you got some sh*#t stuck in the spray bar? How is the tank positioned, is it lower than the carby?
Old 12-08-2007, 07:51 PM
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Default RE: Can't get 58DC to run right...

Doing the pinch test, i can only get the motor to run decently at about 4000 rpm and the motor speeds up a bit before it dies.

I've tried the low speed needle from 3-5.5 turns out and seems to run the best right at 4 turns (between the pinch test and smoothness of running). The high speed doesn't seem to have much effect, it's really bizarre. Anywhere between 1-3 turns out and the RPMs only change by a couple hundred. I have pulled the carb apart a few times and blew it out with compressed air to make sure everything was clean as well. The motor is side mounted and the spray bar is pretty dang close to the center of the fuel tank...I am truly at a loss with his motor as i have never had one run quite this bad. I'm not a motor expert by any means, but I am also not a complete bozo either.

The most weird thing to me is that the idle needle seems to have more of an effect than the high speed.

Do i just need to put more time on this thing and hope for the best?
Old 12-11-2007, 04:58 AM
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Default RE: Can't get 58DC to run right...

Hi *JCB*

Sorry to hear you are having problems with your engine. Please could you let me know the serial number of your engine and we will look into it for you and advice further.

Many thanks

Stephanie
Old 12-11-2007, 04:44 PM
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Default RE: Can't get 58DC to run right...

it seems as if the serial number from the box was torn off a little bit. It looks like 2XX4 where the X's could be 0's 6's or 8's. The motor was purchased from Smith Brother's Hobbies in Northridge, CA USA on March 18, 2007.

Where can i find the serial number on the motor case? It is currently installed on an airplane

Thank you
Old 12-11-2007, 05:00 PM
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Default RE: Can't get 58DC to run right...

The serial number is on the bottom of the engine mounting flange [:@]
So you will have to uninstall it to get to it.
Might not be a bad idea to take the motor out and set it up on the bench to nail these problems.

I have had different issues with installations but when the motor was set up on the bench it ran perfectly. Looking deeper into the the plane setup and things come to light, low tank, crimped line, lack of cooling, etc.
But at least you have the engine on the bench in a nice easy to get at position, which is a safer way to work on it, and quicker in the long run.

If it does prove to be the motor, then you have it out of the plane anyway.
Old 12-11-2007, 05:46 PM
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Default RE: Can't get 58DC to run right...

OK, i was a little off - the serial number is 2584

Thanks for the help mboland!

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