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NEW HONDA VALVES AND A NOS HEAD

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  • NEW HONDA VALVES AND A NOS HEAD

    Hi. I have a nos z50a head. I am going to buy some new Honda valves. Old bloke i spoke with believes if the seats are cut then they should fit fine without lapping in the new valves. Does anyone have any experience with this?

  • #2
    I would agree with that, you could use bearing blue to check the contact is correct

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    • #3
      I do a leak test on mine. Assemble valves and fit spark plug. Fill the combustion chamber with kero and leave it. Check the next day. Lapping is easy anyway. I use a nerf gun bullet with suction cup!!!
      74AŚ3. 78J1. 79R. 82R. 83R. 99R. 74MR50. 75XR75. 98XR70 Crf70. Crf230. Crf450. KLX140.

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      • #4
        Thanks for the help. i'll give it a go without lapping and do a leak test.

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        • #5
          Poor man's bearing blue........coloured grease.
          I'd lap them in, they work pretty hard for a tiny valve. Give them the best start in life. :-)
          Once I thought I was wrong, I was mistaken

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          • #6
            Best practice to check that the seats are correct.

            If you don't have any machinist marking dye you can use a black texta to colour in your valve seat and use a small amount of fine valve grinding paste to lightly check the valve contact to the valve seat.

            Check that there is an even concentric seat pattern, check the width of the valve seat contact, check where on the valve the valve seat contacts the valve face (Should be around the centre of the valve contact face)

            - Here is where I like the valve to valve seat contact just off centre towards the outer edge, this valve has a 1.00mm
            performance seat cut with a three angle valve job, I make the contact wider for road going cylinder head reco's:
            DSC02888.jpg


            This valve to seat contact towards the inner edge of the valve leaves the valve sitting high in the combustion chamber
            and at risk of valve to piston contact if there is limited piston to valve clearance with high lift cams:
            DSC02890.jpg


            For a performance application only I like to get the valve to seat contact out towards the outer edge of the valve face so that the valve sits in the head slightly for better flow.


            Cheers

            Jaimie
            Classic Honda 50's Australia - Visit our online store at - www.classichonda50saustralia.com.au

            PERFORMANCE, REPRODUCTION AND OEM PARTS TO SUIT OLD AND NEW HONDA AND OTHER 4 STROKE MINIBIKES AND MOTORBIKES INCLUDING KAWASAKI, YAMAHA AND SUZUKI.

            Parts to Suit: Honda Z50A, Z50J1, Z50JZ, Z50R, Z50JDM, Z50M, QA50, QR50, MR50, XR50, CRF50, ATC70, CT70, CZ100, MSX125 (Grom), ST70, SL70, XL70, TRX70, XR75, XR80, TRX90, Kawasaki KLX110 and Z125 models to name a few.

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            • #7
              Thanks Jamie. Great advice. I'll grab some valves this week.

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