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OS FS-61 Slowing and/or stopping when remove Glow igniter

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OS FS-61 Slowing and/or stopping when remove Glow igniter

Old 02-13-2021, 03:28 PM
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pawnee_driver
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Default OS FS-61 Slowing and/or stopping when remove Glow igniter

Hi folks,

I just test ran an OS FS-61 which I recently rebuilt and it starts right up (yayyy), but I cannot get it to run below 1/3 throttle without a glow igniter connected.

OAT is about 22-27F, and I'm running 15% Nitro fuel with an OS Type F plug and it seems to have reasonable compression.

Could it be that it's so cold that the plug can't maintain its heat? I've tried playing with the slow mixture, but haven't been able to appreciably change things.

Any thoughts?

Thanks

Matt
Old 02-13-2021, 08:08 PM
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J330
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You should certainly notice some change with idle with a glow igniter on while making idle mixture adjustments. Have you replaced the glow plug with a new one?

Last edited by J330; 02-13-2021 at 08:11 PM.
Old 02-14-2021, 05:57 AM
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pawnee_driver
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Thanks J, that's the first thing I did: I replaced with a new type F plug: no change :-(

Old 02-14-2021, 06:56 AM
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Originally Posted by J330 View Post
You should certainly notice some change with idle with a glow igniter on while making idle mixture adjustments. Have you replaced the glow plug with a new one?
Proper technique ISN'T adjust the needle valve with igniter ON. Unless onboard glow. Of course it is going to slow when the plug stands on its own, verses a battery connected. May not need new plug. Adjust engine without glow igniter. With a 4-stroke, if you don't have experience and a good ear, it must be adjusted by RPM and tach.
Old 02-14-2021, 07:17 AM
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pawnee_driver
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Thanks all, I do know RPM will decrease without the igniter. In my experience, however, the reduction in RPM is around 10-20%, not 50% or more.

Perhaps I didn't make my initial post clear: this is abnormal behavior. Not normal.

What *is* new to me is operating a glow engine in below freezing temps. Hence the question: could the low temps be responsible for cooling the cylinder head to the point that the glow plug is unable to maintain a temperature sufficient to sustain combustion?

So the question stands. Any ideas?
Old 02-14-2021, 07:28 AM
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Originally Posted by pawnee_driver View Post
Thanks all, I do know RPM will decrease without the igniter. In my experience, however, the reduction in RPM is around 10-20%, not 50% or more.

Perhaps I didn't make my initial post clear: this is abnormal behavior. Not normal.

What *is* new to me is operating a glow engine in below freezing temps. Hence the question: could the low temps be responsible for cooling the cylinder head to the point that the glow plug is unable to maintain a temperature sufficient to sustain combustion?

So the question stands. Any ideas?
You're hardcore out running a glow engine below freezing! 😂. Move to warmer climate! It'll be 85 today here in Florida. 😎
I would try to keep the fuel warm inside your house before going to the field. Insulate the fuel jug to keep the fuel temp higher. Maybe go up in nitro. Try a "cold" plug, but it needs an idle bar. It's been too long since I ran a glow engine close to freezing, let alone below freezing.

Old 02-14-2021, 06:08 PM
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try opening that idle screw a bit
Old 02-14-2021, 07:08 PM
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Yup, patience is a virtue... and it would be nice to wait until Spring, but my kids and I are excited to fly this big, light, high dihedral bird (it's school vacation here in New England), and we bought some skis for it, so it's perfect weather... to us! The OS 61 is just right for put putting around at 1/4 throttle and just having a nice day out.

Our other plane is a high wing-loading T6 Texan with teeny weeny retracts which needs a perfect landing every time, or the retracts will bend... :-(

Old 02-14-2021, 07:09 PM
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you bet: I'll mess with the idle screw setting tomorrow, once I put the engine on a test stand, where I can reach the doggone thing

Old 02-15-2021, 03:02 PM
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Hey Matt!

Have you seen these transmitter gloves? They are on eBay, and probably other sources. We used to run to the car for heat in between flights. These would have been great.



There are a lot of different brands and types.

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