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Subject: 8N hydraulic intake control valve adjustment

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Travis Marshall    Posted 12-26-2018 at 17:38:31 [URL] [DELETE]        [Reply] [Email]  
  • 8N hydraulic intake control valve adjustment
  • Iíve scoured the forums for answers to my question but havenít found any references at all.

    I am rebuilding the hydraulic lift pump in my 1947 8N. Completely tore it down and cleaned every possible space. Iím a bit OCD...

    The intake control valve has an adjustable stud and lock nut combination. I presume this is for adjustments perhaps necessary as the spring tension weakens over the years... Is there a published specification for the adjustments to the control valve such as length of plunger or spring length and tension values?

    Thank you in advance

    Tim Daley(MI)    Posted 12-27-2018 at 07:56:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8N hydraulic intake control valve adjustment
  • There is no 'adjustment' procedure. The 8N intake valve was issued in three different sizes. Did you refurbish it and its bushing as well? The bushing has four intake holes held with a cotter pin. There is the valve body, a spring, and a button plug all slipped into the bushing. They don't make those new anymore, except the spring, p/n 8N-697. The valve must have a minimum clearance fit in the bushing but also must move freely. The button plug goes in the bushing large end first. Be sure it is inserted correctly. The spring goes in next and fits over the smaller end. Test in a free state and be sure it is coated well with clean hydraulic oil to test. Did you replace the Safety Relief Valve? That part is available new. The I&T FO-4 Manual has a chapter on R & R'g the hydraulic pump. Dennis Carpenter and JUST8Ns carry the parts. The original 8N operator's manual and the lime green Dealer Service Manual all have chapters on the hydraulic system as well. In addition, we have several documents here in our HOW-TO's forum that may help you. SEE LINK -

    Tim Daley(MI)

    Travis Marshall    Posted 12-27-2018 at 14:23:38 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8N hydraulic intake control valve adjustment
  • Tim,

    Thank you for the excellent clarification.

    I did buff out the valves and bodies for the intake and exhaust ports. I didnít remove the bodies from the pump, but Iíve thoroughly flushed this thing in a solvent tank for a couple hours, brushing away every last speck of grease I could locate on any surface. By time I would have been better off replacing it, but thatís not how my hobby works. =)

    I did replace the relief valve with brand new. Also every cotter pin was replaced.

    This whole project began with three items to fix. 1, Twisted PTO shaft 2, hydraulics that wouldnít react from time to time and 3, the installation of a Howard Aux trans. Anything worth doing, may as well do it thoroughly.

    Cheers, and thank you again.

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