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Over-tight Primer

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Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Sat Feb 17, 2007 12:49 pm Post subject: Over-tight Primer

My mechanic "serviced" the primer in my Yak-52.  I assume he replaced the o-rings but what was most noticeable was that he cranked down excessively on the collar nut.  Thus the primer knob was difficult to move.



Now when i start (cold engine) it runs very, very rough for three or four minutes then smooths out.  After its warm it can be shut down and restarted and it runs relatively smooth.



I backed off the collar nut a bit.  There was a little click and now it slides as it should.  I restarted the engine and moved it from center position to primer position (it ran rough in primer position as it should).



I will start it again tomorrow to see if the problem continues.  My theory is that cranking down on the primer resulted in it feeding through.  I can't tell from the diagrams whether this could be the case and I haven't taken one apart yet.  Any ideas?  Could over-tightening the primer cause this?  Could the primer have been re-assembled incorrectly?  Note that priming to artery will bump up fuel pressure and priming to engine will put fuel in the intake - so the primer appears to work as it should.

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viperdoc(at)mindspring.co
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Posted: Sat Feb 17, 2007 6:47 pm Post subject: Over-tight Primer

Scooter,

It really sounds like you mechanic just over tightened the knarled nut

(collar nut) at the base of the plunger. By backing off on the tension, it

became easier to move and therefor prime the engine. Also try spraying some

LPS spray on the plunger with it out and cycle it a few times to loosen it

up also. With it being extremely tight, you were probably not getting the

ports completely closed during engine start.

Doc 

 	  Quote: 	
		   [Original Message]

 From: Scooter <yakk52(at)verizon.net>

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

 Date: 2/17/2007 2:55:30 PM

 Subject: Over-tight Primer



 



 My mechanic "serviced" the primer in my Yak-52.  I assume he replaced the

o-rings but what was most noticeable was that he cranked down excessively
	


on the collar nut.  Thus the primer knob was difficult to move.

 	  Quote: 	
		  

 Now when i start (cold engine) it runs very, very rough for three or four

minutes then smooths out.  After its warm it can be shut down and restarted
	


and it runs relatively smooth.

 	  Quote: 	
		  

 I backed off the collar nut a bit.  There was a little click and now it

slides as it should.  I restarted the engine and moved it from center
	


position to primer position (it ran rough in primer position as it should).

 	  Quote: 	
		  

 I will start it again tomorrow to see if the problem continues.  My

theory is that cranking down on the primer resulted in it feeding through. 
	


I can't tell from the diagrams whether this could be the case and I haven't

taken one apart yet.  Any ideas?  Could over-tightening the primer cause

this?  Could the primer have been re-assembled incorrectly?  Note that

priming to artery will bump up fuel pressure and priming to engine will put

fuel in the intake - so the primer appears to work as it should.

 	  Quote: 	
		  



 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=95719#95719

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Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Sun Feb 18, 2007 9:20 am Post subject: Re: Over-tight Primer

That was it.  It started fine this morning and ran smoothly.  Apparently if you crank down on the primer it will bleed through to the supercharger housing even with the primer handle centered.  Note that the primer really has to be torqued down in a ridiculous fashion.

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