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Valve Lash Adjustment

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cpayne(at)joimail.com
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Posted: Sat Apr 29, 2006 4:38 am Post subject: Valve Lash Adjustment

The principal reason for routine checking of valve lash is due to wear. Wear between the valve and seat mostly.The reason for having valve lash is that the valve train expands with heat and tends to tighten up at operating temperature.  Excessive lash can lead to losses in combustion effiency and a buildup of deposits on the valve and seat, leading to burning, etc.

  

 The problem with adjusting lash hot is that the other cylinders are cooling while one is being adjusted. The result may be not enough lash on a cylinder which causes a "sticking" spot during air start due to air escaping through the valve, or a loss of compression after the valve train heats up; which means the valve really never closes during the compression stroke.

  

 I check mine cold, and on more than one cam lobe. Remember that there are 4 intake lobes and 4 exhaust lobes for 9 cylinders. If a cam lobe experiences more wear than the other lobes, valve lash is excessive for each valve train that the lobe opens. On a tired old Huosai, I measured a .002" difference in lobes. Upon teardown, there was pitting on valve,  seats, and cam lobes due to sitting in storage for a long time without "pickling". Of course the Chinese logbook showed 15 day runups, but the handwriting, even in Chinese looked identical for every entry :>(

  

  

 Craig Payne

 cpayne(at)joimail.com (cpayne(at)joimail.com)

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YakL1(at)aol.com
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Posted: Sat Apr 29, 2006 11:15 am Post subject: Valve Lash Adjustment

In a message dated 4/29/2006 5:39:34 AM Pacific Standard Time,  cpayne(at)joimail.com writes:

  	  Quote: 	
		  On a    tired old Huosai, I measured a .002" difference in lobes. Upon teardown, there    was pitting on valve,  seats, and cam lobes due to sitting in storage for    a long time without "pickling". Of course the Chinese logbook showed 15 day    runups, but the handwriting, even in Chinese looked identical for every entry    : 	
  

 Have you been making this daily entry or am I supposed to do  it?

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