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pa3arw(at)euronet.nl
Guest

Posted: Sat Sep 04, 2010 11:43 am Post subject: Compression

Yakkers,



The engine 

of my Yak52 has recently been removed in order to be repaired in Lithuania.

Problem: 5 cilinders having no or almost no compression.

Engine has always been maintained properly and compression checked regularly

up to this moment.

Any thoughts/ideas......???



Hans Oortman

YAK52 RA3326K

Netherlands

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Sat Sep 04, 2010 12:22 pm Post subject: Compression

Nice place to have it overhauled. But if you are looking for constructive comments You should at least tell the hours of your engine and at best tell its history.



If I remember well, and I do, Richard Goode have a very professionnal place to overhaul the M14P.

  

Didier.



2010/9/4 Hans Oortman <pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)>

 	  Quote: 	
		    --> Yak-List message posted by: Hans Oortman <pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)>

 

 Yakkers,

 

 The engine

 of my Yak52 has recently been removed in order to be repaired in Lithuania.

 Problem: 5 cilinders having no or almost no compression.

 Engine has always been maintained properly and compression checked regularly

 up to this moment.

 Any thoughts/ideas......???

 

 Hans Oortman

 YAK52 RA3326K

 Netherlands

 

 

 

 ===========

 rget="_blank">http://www.matronics.com/Navigator?Yak-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 	


-- 

Didier BLOUZARD

didier.blouzard(at)gmail.com (didier.blouzard(at)gmail.com)

0624243672

  [quote][b]

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

talew(at)bellsouth.net
Guest

Posted: Sat Sep 04, 2010 12:50 pm Post subject: Compression

Could be a stuck valve . I found it is usually the exaust valve that

sticks it is easy to fix . If the valve snapped off that is really bad . 

I could be wrong .

Terry



---

pa3arw(at)euronet.nl
Guest

Posted: Sat Sep 04, 2010 12:58 pm Post subject: Compression

Didier,

 

 The engine has 220hrs since major overhaul. It was overhauled in Voronezh and after that installed on my Yak52.

 No further specifics. Engine has always been running within its limits and never been really pushed to its limits.

 Ran 80% of its time on Avgas and the remainder on a 50-50 mixture of Mogas and Avgas.

 No excessive oil consumption: i.e. 0.5 l/hr during overland cruise and 1 l/hr during aerobatics.

 

 What else can I say??

 

 Hans

 

 

 Op 04-09-10 22:13, Didier Blouzard <[url=didier.blouzard(at)gmail.com]didier.blouzard(at)gmail.com[/url]> schreef:

 

 [quote]Nice place to have it overhauled. But if you are looking for constructive comments You should at least tell the hours of your engine and at best tell its history.

 

 If I remember well, and I do, Richard Goode have a very professionnal place to overhaul the M14P.

 

 Didier.

 

 2010/9/4 Hans Oortman <[url=pa3arw(at)euronet.nl]pa3arw(at)euronet.nl[/url]>

  	  Quote: 	
		  --> Yak-List message posted by: Hans Oortman <[url=pa3arw(at)euronet.nl]pa3arw(at)euronet.nl[/url]>

 

 Yakkers,

 

 The engine

 of my Yak52 has recently been removed in order to be repaired in Lithuania.

 Problem: 5 cilinders having no or almost no compression.

 Engine has always been maintained properly and compression checked regularly

 up to this moment.

 Any thoughts/ideas......???

 

 Hans Oortman

 YAK52 RA3326K

 Netherlands

 

 

 

 ===========

 	
rget="_blank">mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

 ===========

 mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

 ===========

 le, List Admin.

 ="_blank">mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

 ===========

 

 

 

 

 

 [b]

pfstelwagon(at)earthlink.
Guest

Posted: Sat Sep 04, 2010 12:59 pm Post subject: compression

You might try adjusting the valves sounds strange  that you have 5 cylinders with no compression.

  

 Frank

  [quote][b]

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Sat Sep 04, 2010 1:07 pm Post subject: Compression

OK thanks Hans,

That's fine Hans.

I'll check around with my friends, and come back to you if any relevant suggestion.

Good luck



best regards



2010/9/4 Hans Oortman <pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)>

   	  Quote: 	
		       Didier,

 

 The engine has 220hrs since major overhaul. It was overhauled in Voronezh and after that installed on my Yak52.

 No further specifics. Engine has always been running within its limits and never been really pushed to its limits.

 Ran 80% of its time on Avgas and the remainder on a 50-50 mixture of Mogas and Avgas.

 No excessive oil consumption: i.e. 0.5 l/hr during overland cruise and 1 l/hr during aerobatics.

 

 What else can I say??

 

 Hans

 

 

 Op 04-09-10 22:13, Didier Blouzard <didier.blouzard(at)gmail.com> schreef:

 

  	  Quote: 	
		  Nice place to have it overhauled. But if you are looking for constructive comments You should at least tell the hours of your engine and at best tell its history.

   

 If I remember well, and I do, Richard Goode have a very professionnal place to overhaul the M14P.

 

 Didier.

 

 2010/9/4 Hans Oortman <pa3arw(at)euronet.nl>

  	  Quote: 	
		  --> Yak-List message posted by: Hans Oortman <pa3arw(at)euronet.nl>

   

 Yakkers,

 

 The engine

 of my Yak52 has recently been removed in order to be repaired in Lithuania.

 Problem: 5 cilinders having no or almost no compression.

 Engine has always been maintained properly and compression checked regularly

 up to this moment.

 Any thoughts/ideas......???

 

 Hans Oortman

 YAK52 RA3326K

 Netherlands

 

 

 



 ===========

 	
rget="_blank">mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

   ===========

 mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

 ===========

 le, List Admin.

 ="_blank">mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

   ===========

 

 

 

 

 

 	
        	  Quote: 	
		  



et="_blank">http://www.matronics.com/Navigator?Yak-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	




	


-- 

Didier BLOUZARD

didier.blouzard(at)gmail.com (didier.blouzard(at)gmail.com)

0624243672

  [quote][b]

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

talew(at)bellsouth.net
Guest

Posted: Sat Sep 04, 2010 2:02 pm Post subject: Compression

Please disregard my previous post . 

 I misread the information .

 Thought you meant #5 cylinder . Stills sounds like a valve problem internal

 to the engine.

 Terry



 

   From: Hans Oortman <pa3arw(at)euronet.nl>

To: yak-list(at)matronics.com

Sent: Sat, September 4, 2010 4:58:37 PM

Subject: Re: Compression



Didier,



The engine has 220hrs since major overhaul. It was overhauled in Voronezh and after that installed on my Yak52.

No further specifics. Engine has always been running within its limits and never been really pushed to its limits.

Ran 80% of its time on Avgas and the remainder on a 50-50 mixture of Mogas and Avgas.

No excessive oil consumption: i.e. 0.5 l/hr during overland cruise and 1 l/hr during aerobatics.



What else can I say??



Hans

Op 04-09-10 22:13, Didier Blouzard <didier.blouzard(at)gmail.com> schreef:



 [quote]Nice place to have it overhauled. But if you are looking for constructive comments You should at least tell the hours of your engine and at best tell its history.



If I remember well, and I do, Richard Goode have a very professionnal place to overhaul the M14P.



Didier.



2010/9/4 Hans Oortman <pa3arw(at)euronet.nl>

  	  Quote: 	
		  --> Yak-List message posted by: Hans Oortman <pa3arw(at)euronet.nl>



Yakkers,



The engine

of my Yak52 has recently been removed in order to be repaired in Lithuania.

Problem: 5 cilinders having no or almost no compression.

Engine has always been maintained properly and compression checked regularly

up to this moment.

Any thoughts/ideas......???



Hans Oortman

YAK52 RA3326K

Netherlands



===========

	
rget="_blank">http://www.matronics.com/Navigator?Yak-List <mailto:pa3arw(at)euronet.nl (pa3arw(at)euronet.nl)> 

===========

http://forums.matronics.com <

yakplt(at)yahoo.com
Guest

Posted: Sat Sep 04, 2010 4:09 pm Post subject: Compression

The question I would ask is: 



How many hours has it been since someone adjusted your valves?  



Everyone seems to be on the same page of music here and is thinking valves.  But are you actually saying that FIVE CYLINDERS HAVE LITTLE OR NO COMPRESSION?  Not.. the #5 cylinder, but FIVE INDIVIDUAL CYLINDERS?  Wow.  



One thought is:  If someone managed to really screw up the valve lash and tightened the things down too much, your valves might never be allowed to fully close.  If that happened, your valves would burn up pretty darn quickly.  



Lots of other things comes to mind.  But cut to the chase.  Get a bore-scope and LOOK inside those cylinders.  Look at the cylinder walls for scoring and look at the valves for signs of burning and high temps.  



When you run a compression test, what happens to the air you are putting in there?  Is it coming out the exhaust, or is it coming out the intake?  A good mechanic ought to be able to tell you what the heck is going on.  Just saying: "Five Cylinders have little or no compression" tells me that you might want to consider getting someone who knows a little more what they are doing.  I am not a great engine mech.  But even I know a little about the basics, and you should not have to go to the YAK list for an answer.  Not that I (or anyone else) minds, but it is just that a good mechanic should be able to tell you.  



Mark Bitterlich

--- On Sat, 9/4/10, Hans Oortman <pa3arw(at)euronet.nl> wrote:



 	  Quote: 	
		   From: Hans Oortman <pa3arw(at)euronet.nl>

 Subject: Compression

 To: yak-list(at)matronics.com

 Date: Saturday, September 4, 2010, 3:43 PM

 

 Hans Oortman <pa3arw(at)euronet.nl>

 

 Yakkers,

 

 The engine 

 of my Yak52 has recently been removed in order to be

 repaired in Lithuania.

 Problem: 5 cilinders having no or almost no compression.

 Engine has always been maintained properly and compression

 checked regularly

 up to this moment.

 Any thoughts/ideas......???

 

 Hans Oortman

 YAK52 RA3326K

 Netherlands

 

 

 

 Forum -

 FAQ,

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

cjpilot710(at)aol.com
Guest

Posted: Sat Sep 04, 2010 6:11 pm Post subject: Compression

This really sounds interesting!  I agree with Mark on a lot here.

    

   If you have burnt exhaust valves, pressurizing the cylinder while the piston is a TDC, you will hear air in the exhaust stack.  The same will happen if the valve is not fully seated.  If the intake valve is brunt or not fully closed, you'll hear air in the carburetor intake.  If the rings are bad you will hear air in case, when you put your ear to the case breather.

    

   Also starting the engine would be harder.  Since both valves need to be closed with the piston slightly passed TDC and on the power stroke.

   One time on my HS6 I had a brunt exhaust valve.  Its only give away was occasionally it would not start kick over when I hit the start button.  I would need to get out of the airplane, and pull the prop though one blade.  The engine seem to run OK otherwise.  Its wasn't until I did a compression check at the annual, did I find the problem!  One of those duhhhh moments.

    

   You might want to check the little pop it valve on the cylinders.  If these are not seated, (crap under their seats) they could allow pressurized air to escape back toward the starter valve.

    

   Let us know what they find.  For an M-14p to have that many cylinders so low with as little time on the engine as you say, is very usual.

    

   Jim "Pappy" Goolsby

 

 

   

 

 

   --

pa3arw(at)euronet.nl
Guest

Posted: Sun Sep 05, 2010 12:19 am Post subject: Compression

Mark,

You know how it goes; I want to have an answer sooner and quicker than those

mechanics can work.....

Yeah...I have a very good mechanic(s) working on it. The valves have been

checked a year and a halve ago and nothing was found wrong.

Cilinders 4, 5, 6, 7 and 8 have no compression left. The air seems to get

out via the exhaust valve, you can hear the hissing.....but the thing that

bothers me really is: why 5 cilinders at the same time???

It could or can only(?)be a common thing to all those five cilinders?? If

that is the case it can not be the individual exhaust valve.

The only reasons I can come up with are:

1. Fuel....too lean...but this should have an effect on the cilinder head

temp which has never been in the red zone at all.

2. The air start system...something in the "spider", may be....

I'll keep you all informed on the progress the mechanics are making. They

promised me to send some pictures as well...

W'll keep you posted.

Hans

Op 05-09-10 02:09, Yak Pilot <yakplt(at)yahoo.com> schreef:

 	  Quote: 	

 The question I would ask is:

 How many hours has it been since someone adjusted your valves?

 Everyone seems to be on the same page of music here and is thinking valves.

 But are you actually saying that FIVE CYLINDERS HAVE LITTLE OR NO COMPRESSION?

 Not.. the #5 cylinder, but FIVE INDIVIDUAL CYLINDERS?  Wow.

 One thought is:  If someone managed to really screw up the valve lash and

 tightened the things down too much, your valves might never be allowed to

 fully close.  If that happened, your valves would burn up pretty darn quickly.

 Lots of other things comes to mind.  But cut to the chase.  Get a bore-scope

 and LOOK inside those cylinders.  Look at the cylinder walls for scoring and

 look at the valves for signs of burning and high temps.

 When you run a compression test, what happens to the air you are putting in

 there?  Is it coming out the exhaust, or is it coming out the intake?  A good

 mechanic ought to be able to tell you what the heck is going on.  Just saying:

 "Five Cylinders have little or no compression" tells me that you might want to

 consider getting someone who knows a little more what they are doing.  I am

 not a great engine mech.  But even I know a little about the basics, and you

 should not have to go to the YAK list for an answer.  Not that I (or anyone

 else) minds, but it is just that a good mechanic should be able to tell you.

 Mark Bitterlich

 --- On Sat, 9/4/10, Hans Oortman <pa3arw(at)euronet.nl> wrote:

> From: Hans Oortman <pa3arw(at)euronet.nl>

> Subject: Compression

> To: yak-list(at)matronics.com

> Date: Saturday, September 4, 2010, 3:43 PM

> 

> Hans Oortman <pa3arw(at)euronet.nl>

> 

> Yakkers,

> 

> The engine 

> of my Yak52 has recently been removed in order to be

> repaired in Lithuania.

> Problem: 5 cilinders having no or almost no compression.

> Engine has always been maintained properly and compression

> checked regularly

> up to this moment.

> Any thoughts/ideas......???

> 

> Hans Oortman

> YAK52 RA3326K

> Netherlands

> 

> 

> 

> Forum -

> FAQ,

>    - MATRONICS WEB FORUMS -

> List Contribution Web Site -

>               -Matt

> Dralle, List Admin.

> 

> 

> 

>

george(at)gesoco.com
Guest

Posted: Sun Sep 05, 2010 5:38 am Post subject: Compression

How often was the engine Run? 



George Coy

CAS Ltd.

714 Airport Rd.

Swanton VT 05488

802-868-5633 off

802-363-5782 cell

george.coy(at)gmail.com

http://coyafct.com/

SKYPE george.coy



--

dsavarese0812(at)bellsout
Guest

Posted: Sun Sep 05, 2010 6:39 am Post subject: Compression

I think I would ask your mechanic to bring the individual  cylinders up to top dead center one at a time and then check the valve gap on  them.   The valve gap should be .010 - .014 (.25-.35 mm) cold per  specification.  Be sure when checking the valve gap the pushrod adjuster  nut is pressed down to relieve the spring pressure.  While holding the  pressure on the adjuster nut, measure the gap 90 degrees perpendicular to  the roller on the rocker arm.  Not in the direction of the roller.  It  would be a good idea to have a bent feeler gauge with the bent tip about   1/2" or so long.  With leaking exhaust valves as you described, it could be  improper valve gap which in turn could cause the exhaust valve to  burn.

 Dennis

  

  

  

 ---

viperdoc(at)mindspring.co
Guest

Posted: Sun Sep 05, 2010 6:41 am Post subject: Compression

I’m betting it is valve adjustment that lead to it. Have the valves been adjusted after every 100 hours of operation?  

Doc  

     

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of cjpilot710(at)aol.com

 Sent: Saturday, September 04, 2010 9:10 PM

 To: yak-list(at)matronics.com

 Subject: Re: Compression  

  

     

This really sounds interesting!  I agree with Mark on a lot here.  

    

   

    

If you have burnt exhaust valves, pressurizing the cylinder while the piston is a TDC, you will hear air in the exhaust stack.  The same will happen if the valve is not fully seated.  If the intake valve is brunt or not fully closed, you'll hear air in the carburetor intake.  If the rings are bad you will hear air in case, when you put your ear to the case breather.  

    

   

    

Also starting the engine would be harder.  Since both valves need to be closed with the piston slightly passed TDC and on the power stroke.  

    

One time on my HS6 I had a brunt exhaust valve.  Its only give away was occasionally it would not start kick over when I hit the start button.  I would need to get out of the airplane, and pull the prop though one blade.  The engine seem to run OK otherwise.  Its wasn't until I did a compression check at the annual, did I find the problem!  One of those duhhhh moments.  

    

   

    

You might want to check the little pop it valve on the cylinders.  If these are not seated, (crap under their seats) they could allow pressurized air to escape back toward the starter valve.  

    

   

    

Let us know what they find.  For an M-14p to have that many cylinders so low with as little time on the engine as you say, is very usual.  

    

   

    

Jim "Pappy" Goolsby  

  

     

--

coolade1

Joined: 05 Aug 2010
Posts: 3

Posted: Sun Sep 05, 2010 9:50 am Post subject: Compression

Your problem is most likely a carbon on the exhaust valves, we recently had the same situation on a compression test on two cylinders--removed one and had valves reground, noticed that the valve and seats were not burned but merely carboned.  The next cylinder I decided to try and old trick my father used to do on stuck valves. remove spark plugs insert about six feet of cotton rope into cylinder, bring up towards compression to prevent valves from moving when you depress valve springs to remove keepers. Remove exhaust tube. attach slow rpm drill motor to valve, insert small brush into exhaust port to reach valve seat, start with course compound then go to fine compound running drill motor to seat the valve. wash with contact cleaner or automotive brake cleaner. the cleaner and valve compound is absorber by the cotton rope. bring cylinder back towards compression and compress valve spring and reinsert keepers--whole operation took less than three hours.  compression came back to 75/80.

On Sep 5, 2010, at 9:37 AM, A. Dennis Savarese wrote:

[quote]I think I would ask your mechanic to bring the individual cylinders up to top dead center one at a time and then check the valve gap on them.   The valve gap should be .010 - .014 (.25-.35 mm) cold per specification.  Be sure when checking the valve gap the pushrod adjuster nut is pressed down to relieve the spring pressure.  While holding the pressure on the adjuster nut, measure the gap 90 degrees perpendicular to the roller on the rocker arm.  Not in the direction of the roller.  It would be a good idea to have a bent feeler gauge with the bent tip about  1/2" or so long.  With leaking exhaust valves as you described, it could be improper valve gap which in turn could cause the exhaust valve to burn.

Dennis

 

 

 

---

pa3arw(at)euronet.nl
Guest

Posted: Sun Sep 05, 2010 11:29 am Post subject: Compression

Doc,



Absolutely....but 5 cilinders wrongly adjusted by a mechanic who¹s done

hundreds of M14P¹s????Mmmmm?



Hans

Op 05-09-10 16:09, Roger Kemp M.D. <viperdoc(at)mindspring.com> schreef:



[quote] I¹m betting it is valve adjustment that lead to it. Have the valves been

 adjusted after every 100 hours of operation?

 Doc

  

 

 From: owner-yak-list-server(at)matronics.com

 [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of cjpilot710(at)aol.com

 Sent: Saturday, September 04, 2010 9:10 PM

 To: yak-list(at)matronics.com

 Subject: Re: Compression

  

 

 This really sounds interesting!  I agree with Mark on a lot here.

 

  

 

 If you have burnt exhaust valves, pressurizing the cylinder while the piston

 is a TDC, you will hear air in the exhaust stack.  The same will happen if the

 valve is not fully seated.  If the intake valve is brunt or not fully closed,

 you'll hear air in the carburetor intake.  If the rings are bad you will hear

 air in case, when you put your ear to the case breather.

 

  

 

 Also starting the engine would be harder.  Since both valves need to be closed

 with the piston slightly passed TDC and on the power stroke.

 

 One time on my HS6 I had a brunt exhaust valve.  Its only give away was

 occasionally it would not start kick over when I hit the start button.  I

 would need to get out of the airplane, and pull the prop though one blade

pa3arw(at)euronet.nl
Guest

Posted: Sun Sep 05, 2010 11:36 am Post subject: Compression

George,



On a very regular basis with the exception of the winter time when it ran

only once every 2 or 3 weeks.



Hans



Op 05-09-10 15:28, George Coy <george(at)gesoco.com> schreef:



[quote] 

 

 How often was the engine Run?

 

 George Coy

 CAS Ltd.

 714 Airport Rd.

 Swanton VT 05488

 802-868-5633 off

 802-363-5782 cell

 george.coy(at)gmail.com

 http://coyafct.com/

 SKYPE george.coy

 

 --

yakplt(at)yahoo.com
Guest

Posted: Sun Sep 05, 2010 3:40 pm Post subject: Compression

Excuse me for adding a comment slightly off topic, but .... 

  

 1.  Doing what Dennis suggests makes perfect sense to me.

     

 And... a comment was made: "How could a mechanic misadjust so many cylinders? " Easy.  All that is needed is a cam lobe that is worn much differently from the others, and the mech adjusted all the cylinders to the worn cam lobe.  Then when the other ones hit the rocker, they end up not allowing the valve to fully close.  Not a gross error.  Just too tight.  The valve does not completely close, very high temp exhaust valves erode the seat, and POOF.   Might take awhile to happen.  A year or so?     I am not putting money on this being the problem mind you, just offering a circumstance that MIGHT explain it.  

  

 2.  A STRONG CAUTION on what Adrian Hale wrote regarding lapping valves in place.  

  

 If you are going to do the Indian Rope Trick on a cylinder in order to get an exhaust valve to seat, be advised that is does indeed work.  And it works pretty darn well for the lower cylinders... why just the lower ones?  Because all that grinding compound pretty much ends up falling out the spark plug holes.   Blow some compressed air in there, be careful and you can be PRETTY sure you get it all out.  THIS IS NOT THE CASE FOR THE UPPER CYLINDERS!  When you try this trick with those, it is VERY VERY possible that some of that grinding compound will make it past the rope and down into the rings.  

  

 So what do you think can happen when you start an engine up with grinding compound stuck in the piston rings?  

  

 This is not "theory".  Yes, I actually did this.  I also ended up having two rings cracking in half, and had to hone the cylinder.  I was actually lucky that it did not do more damage.  

  

 So yes, it is a neat trick.  Yes, it can indeed work.  It can also destroy a cylinder. QUICKLY!   Especially on the top ones.  

  

 If   *I*   EVER run into a problem like this again, top or bottom, that darn cylinder is coming OFF the engine, and we are going to fix it on the bench.  But, that's just me.  You roll the dice, you take your chances.  

  

 Mark Bitterlich

  

  

  

  

 

--- On Sun, 9/5/10, adrian hale <coolade1(at)att.net> wrote:



 [quote]

From: adrian hale <coolade1(at)att.net>

Subject: Re: Compression

To: yak-list(at)matronics.com

Date: Sunday, September 5, 2010, 1:50 PM



 Your problem is most likely a carbon on the exhaust valves, we recently had the same situation on a compression test on two cylinders--removed one and had valves reground, noticed that the valve and seats were not burned but merely carboned.  The next cylinder I decided to try and old trick my father used to do on stuck valves. remove spark plugs insert about six feet of cotton rope into cylinder, bring up towards compression to prevent valves from moving when you depress valve springs to remove keepers. Remove exhaust tube. attach slow rpm drill motor to valve, insert small brush into exhaust port to reach valve seat, start with course compound then go to fine compound running drill motor to seat the valve. wash with contact cleaner or automotive brake cleaner. the cleaner and valve compound is absorber by the cotton rope. bring cylinder back towards compression and compress valve spring and reinsert keepers--whole operation  took less than three hours.  compression came back to 75/80.

  On Sep 5, 2010, at 9:37 AM, A. Dennis Savarese wrote:

 [quote]  I think I would ask your mechanic to bring the individual cylinders up to top dead center one at a time and then check the valve gap on them.   The valve gap should be .010 - .014 (.25-.35 mm) cold per specification.  Be sure when checking the valve gap the pushrod adjuster nut is pressed down to relieve the spring pressure.  While holding the pressure on the adjuster nut, measure the gap 90 degrees perpendicular to the roller on the rocker arm.  Not in the direction of the roller.  It would be a good idea to have a bent feeler gauge with the bent tip about  1/2" or so long.  With leaking exhaust valves as you described, it could be improper valve gap which in turn could cause the exhaust valve to burn.

 Dennis

  

  

  

 ---

viperdoc(at)mindspring.co
Guest

Posted: Sun Sep 05, 2010 8:17 pm Post subject: Compression

Hans,  

As you, it really surprises me that you would have 5 leaking cylinders. One cylinder with the rings align so as to lose compression  I can rationalize. One or two cylinders with leaking exhaust valves I can see too but generally not in 200 hours total time unless there was a mistake in valve lash adjustment. The guys in Lithuania will tell the tale soon. Sorry you are having to go through this. Will interested in hearing what the cause is.  

Doc  

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Hans Oortman

 Sent: Sunday, September 05, 2010 2:27 PM

 To: yak-list(at)matronics.com

 Subject: Re: Compression  

Doc,

 Absolutely....but 5 cilinders wrongly adjusted by a mechanic who’s done hundreds of M14P’s????Mmmmm?

 Hans

 Op 05-09-10 16:09, Roger Kemp M.D. <[url=viperdoc(at)mindspring.com]viperdoc(at)mindspring.com[/url]> schreef:  

I’m betting it is valve adjustment that lead to it. Have the valves been adjusted after every 100 hours of operation?

 Doc

 From: mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of [url=cjpilot710(at)aol.com]cjpilot710(at)aol.com[/url]

 Sent: Saturday, September 04, 2010 9:10 PM

 To: [url=yak-list(at)matronics.com]yak-list(at)matronics.com[/url]

 Subject: Re: Compression

 This really sounds interesting!  I agree with Mark on a lot here.

 If you have burnt exhaust valves, pressurizing the cylinder while the piston is a TDC, you will hear air in the exhaust stack.  The same will happen if the valve is not fully seated.  If the intake valve is brunt or not fully closed, you'll hear air in the carburetor intake.  If the rings are bad you will hear air in case, when you put your ear to the case breather.

 Also starting the engine would be harder.  Since both valves need to be closed with the piston slightly passed TDC and on the power stroke.

 One time on my HS6 I had a brunt exhaust valve.  Its only give away was occasionally it would not start kick over when I hit the start button.  I would need to get out of the airplane, and pull the prop though one blade.  The engine seem to run OK otherwise.  Its wasn't until I did a compression check at the annual, did I find the problem! One of those duhhhh moments.

 You might want to check the little pop it valve on the cylinders.  If these are not seated, (crap under their seats) they could allow pressurized air to escape back toward the starter valve.

 Let us know what they find.  For an M-14p to have that many cylinders so low with as little time on the engine as you say, is very usual.

 Jim "Pappy" Goolsby

 -----Original Message-----

 From: Yak Pilot <[url=yakplt(at)yahoo.com]yakplt(at)yahoo.com[/url]>

 To: [url=yak-list(at)matronics.com]yak-list(at)matronics.com[/url]

 Sent: Sat, Sep 4, 2010 8:09 pm

 Subject: Re: Compression

 --> Yak-List message posted by: Yak Pilot <[url=yakplt(at)yahoo.com]yakplt(at)yahoo.com[/url]>

 The question I would ask is: 

 How many hours has it been since someone adjusted your valves?  

 Everyone seems to be on the same page of music here and is thinking valves.  But 

 are you actually saying that FIVE CYLINDERS HAVE LITTLE OR NO COMPRESSION?  

 Not.. the #5 cylinder, but FIVE INDIVIDUAL CYLINDERS?  Wow.  

 One thought is:  If someone managed to really screw up the valve lash and 

 tightened the things down too much, your valves might never be allowed to fully 

 close.  If that happened, your valves would burn up pretty darn quickly.  

 Lots of other things comes to mind.  But cut to the chase.  Get a bore-scope and 

 LOOK inside those cylinders.  Look at the cylinder walls for scoring and look at 

 the valves for signs of burning and high temps.  

 When you run a compression test, what happens to the air you are putting in 

 there?  Is it coming out the exhaust, or is it coming out the intake?  A good 

 mechanic ought to be able to tell you what the heck is going on.  Just saying: 

 "Five Cylinders have little or no compression" tells me that you might want to 

 consider getting someone who knows a little more what they are doing.  I am not 

 a great engine mech.  But even I know a little about the basics, and you should 

 not have to go to the YAK list for an answer.  Not that I (or anyone else) 

 minds, but it is just that a good mechanic should be able to tell you.  

 Mark Bitterlich

 --- On Sat, 9/4/10, Hans Oortman <[url=pa3arw(at)euronet.nl]pa3arw(at)euronet.nl[/url]> wrote:

 > From: Hans Oortman <[url=pa3arw(at)euronet.nl]pa3arw(at)euronet.nl[/url]>

 > Subject: Compression

 > To: [url=yak-list(at)matronics.com]yak-list(at)matronics.com[/url]

 > Date: Saturday, September 4, 2010, 3:43 PM

 > --> Yak-List message posted by:

 > Hans Oortman <[url=pa3arw(at)euronet.nl]pa3arw(at)euronet.nl[/url]>

 > 

 > Yakkers,

 > 

 > The engine 

 > of my Yak52 has recently been removed in order to be

 > repaired in Lithuania.

 > Problem: 5 cilinders having no or almost no compression.

 > Engine has always been maintained properly and compression

 > checked regularly

 > up to this moment.

 > Any thoughts/ideas......???

 > 

 > Hans Oortman

 > YAK52 RA3326K

 > Netherlands

 > 

 > 

 > 

 > Forum -

 > FAQ,

 >    - MATRONICS WEB FORUMS -

 > List Contribution Web Site -

 >               -Matt

 > Dralle, List Admin.

 > 

 > 

 > 

 > 

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george.coy(at)gmail.com
Guest

Posted: Mon Sep 06, 2010 4:47 am Post subject: Compression

Thanks. I apologize if I am asking questions that were already answered, I

came into this discussion in the middle of it. 



A couple of other questions:

1.Were the compressions taken hot or cold?

2. What was the orifice reading on the compression tester and what were the

actual readings?

3. Were they all leaking by the exhaust valves?

4. Did you try "STAKING" the valves?

5. Did you take the aircraft out run it up to temperatures, fly it around

the field and then re check the compressions?



Bear in mind that compression tests with the piston at top dead center only

give an indication of health of the cylinder valves and rings at a moment in

time. It is a guide. History of compressions is just as important. A single

set of readings can be misleading. IF they were taken with cold cylinders

after a period of inactivity, I would certain ally run I up, fly it and re

check them before sending the engine out for overhaul.  



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