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byronmfox(at)gmail.com
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 Posted: Sat Jul 06, 2019 12:58 pm Post subject: M14-P quandary |
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I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the engine runs rough for about 10-15 seconds, and then smooths out. Gets one's attention.
Grounding testing, chocked and chained down, I get the same result at full power, and black smoke is observed coming out of the port (left) exhaust stack.
During the roughness:
- Both mags check OK
- Throttle movement has no effect
- Wobble pumping has no effect
- Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
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markbitterlich(at)embarqm
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| Posted: Sat Jul 06, 2019 1:17 pm Post subject: M14-P quandary |
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Start with a compression test.Next make it happen on ground as badly as possible then shut down engine pull plugs and examine them.
Look for induction air leaks
Look for any leakage through wobble pump.
While it is running badly try to use IR heat gun to get temps on cylinders and tubes. Yes, pretty dangerous and lots of air moving.
Check intake drains, assuming you have installed them, for bad leaks.
-------- Original message --------
From: Byron Fox <byronmfox(at)gmail.com>
Date: 7/6/19 16:57 (GMT-05:00)
To: Yak LIst <yak-list(at)matronics.com>
Subject: Yak-List: M14-P quandary
I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the engine runs rough for about 10-15 seconds, and then smooths out. Gets one's attention.
Grounding testing, chocked and chained down, I get the same result at full power, and black smoke is observed coming out of the port (left) exhaust stack.
During the roughness:
- Both mags check OK
- Throttle movement has no effect
- Wobble pumping has no effect
- Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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dsavarese0812(at)bellsout
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| Posted: Sat Jul 06, 2019 1:53 pm Post subject: M14-P quandary |
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Add a quart of Marvel Mystery Oil to the oil and go fly the airplane for
an hour or two.?? The MMO tends to clean the valve stems and valve guides
of the varnish buildup that causes valve(s) to stick. Even a couple of
quarts won't hurt it.
Dennis
A. Dennis Savarese
334-546-8182 (mobile)
www.yak-52.com
Skype - Yakguy1
On 7/6/2019 4:57 PM, Byron Fox wrote:
| Quote: | I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the
engine runs rough for about 10-15 seconds, and then smooths out. Gets
one's attention.
Grounding testing, chocked and chained down, I get the same result at
full power, and black smoke is observed coming out of the port (left)
exhaust stack.
During the roughness:
1. Both mags check OK
2. Throttle movement has no effect
3. Wobble pumping has no effect
4. Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why
briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
|
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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terrycalloway(at)mac.com
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| Posted: Sun Jul 07, 2019 4:29 am Post subject: M14-P quandary |
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I've see lots of other good advice being posted and agree trying those points too.
Don't overlook the effects of one or a few bad spark plugs can cause. Also to isolate a cylinder you might use a heat sensor gun if you don't have multi-port cyl gauge.
Good luck.
On July 6, 2019 at 4:05 PM, Byron Fox <byronmfox(at)gmail.com> wrote:
| Quote: | I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the engine runs rough for about 10-15 seconds, and then smooths out. Gets one's attention.
Grounding testing, chocked and chained down, I get the same result at full power, and black smoke is observed coming out of the port (left) exhaust stack.
During the roughness:
- Both mags check OK
- Throttle movement has no effect
- Wobble pumping has no effect
- Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
|
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http://www.matronics.com/Navigator?Yak-List |
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Mon Jul 15, 2019 5:30 am Post subject: M14-P quandary |
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Blitz, Black smoke from the exhaust normally means it is running rich. There is but here though with the single carb and the supercharger. Do all Mark says. Pay attention to glan nuts on the right side for induction leaks. Pay attention to all of them for that matter but especially the right. Also check you carburetor filter screen. Flappers in the fuel line can accumulate there obstructing the fuel flow.
Doc
Sent from my iPad
On Jul 6, 2019, at 3:57 PM, Byron Fox <byronmfox(at)gmail.com (byronmfox(at)gmail.com)> wrote:
| Quote: | I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the engine runs rough for about 10-15 seconds, and then smooths out. Gets one's attention.
Grounding testing, chocked and chained down, I get the same result at full power, and black smoke is observed coming out of the port (left) exhaust stack.
During the roughness:
- Both mags check OK
- Throttle movement has no effect
- Wobble pumping has no effect
- Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
|
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Yak-List |
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Viperdoc |
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markbitterlich(at)embarqm
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| Posted: Tue Jul 16, 2019 12:52 pm Post subject: M14-P quandary |
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Blitz,
Going over this again after reading Doc’s inputs, if the compression is good, and there are no induction leaks, and you have no leaks in your intake drain kit (easy to overlook that issue) it is hard to believe it is a fuel issue in any way. If a high performance car engine was doing this, I would immediately check for a failed or cracked valve spring as well as checking valve lash. It is hard for me to imagine the exhaust valve sticking at high RPM and then “unsticking” as soon as you reduce RPM. But my thoughts at this point would primarily be on ignition, assuming everything else is OK. You are NOT using the stock ignition wiring correct? If it IS stock ignition wiring, a cross fire to another wire in the tube could easily cause this. Have you done a mag check WHILE THIS ISSUE IS HAPPENING? I understand a normal MAG check is A-OK, but have you run the same mag check when it is belching smoke? If it is doing this on the ground, and you don’t really like the idea of doing a mag check at full power (yes, I get that doing that might be worth thinking twice about), then simply run on just one MAG and run it up to full power and then back, and then try it on the other mag running alone. Simple and worth seeing what happens.
Good luck.
Mark
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Roger Kemp
Sent: Monday, July 15, 2019 9:26 AM
To: yak-list(at)matronics.com
Subject: Re: M14-P quandary
Blitz,
Black smoke from the exhaust normally means it is running rich. There is but here though with the single carb and the supercharger. Do all Mark says. Pay attention to glan nuts on the right side for induction leaks. Pay attention to all of them for that matter but especially the right. Also check you carburetor filter screen. Flappers in the fuel line can accumulate there obstructing the fuel flow.
Doc
Sent from my iPad
On Jul 6, 2019, at 3:57 PM, Byron Fox <byronmfox(at)gmail.com (byronmfox(at)gmail.com)> wrote:
| Quote: |
I'll endeavor to be succinct.
About 1-2 minutes after takeoff in our CJ, climbing at 2900 rpm, the engine runs rough for about 10-15 seconds, and then smooths out. Gets one's attention.
Grounding testing, chocked and chained down, I get the same result at full power, and black smoke is observed coming out of the port (left) exhaust stack.
During the roughness:
- Both mags check OK
- Throttle movement has no effect
- Wobble pumping has no effect
- Prop movement has no effect
The analysis so far is a sticking exhaust valve, but which one? Why briefly at high power and consequently high heat?
Compression tests are fine.
Nothing obvious appears when the valve covers are removed.
Would appreciate your thoughts.
Thanks,
... Blitz
Byron M. Fox
415-307-2405
|
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Yak-List |
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