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Thread: Weekend Head Job

  1. #1
    Forum Founder Classic Honda 50's's Avatar
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    Weekend Head Job

    Had a forum member call me from his mechanics workshop saying that his mechanic had broken a few sets of OEM guides trying to install them and that the OEM valves did not fit in the guides

    A few red flags there so I said to grab all the parts get it in the post and I will have a look at it, here is what the head looked like when I opened the box, remember that it is almost 1/2 finished.

    Might have helped if the mechanic would have cleaned the carbon build-up from the exhaust port and guide before driving it out the head, I have had to bin a few heads where the carbon is left on the guide and as the guide is driven out the carbon stays attached to the guide and makes the hole in the head bigger, the new guide will then be loose when installed.

    DSC03643.jpg


    Broken Exhaust Guide No 2, have seen people use centre and pin punches to try and drive guides in and out and this is the result, use the right tool for the job:
    DSC03652.jpg


    The Inlet Guide looked as if it was second hand:
    DSC03654.jpg


    Poor old cam journals were scored as usual but will be ok, look at the rust in the plug hole:
    DSC03658.jpg


    A few too many dead guides for this head:
    DSC03661.jpg


    Clean the head first and inspect it carefully to see if it even worth fixing to start with, I have been sent heads where the owners had spent $500 - $1000 on a head that was stuffed to start with:
    DSC03667.jpg


    Here is where I like to start, spotlessly clean and then inspect the head carefully before spending any more time and money:
    DSC03672.jpg


    Parts ready for the rebuild:
    DSC03733.jpg


    In the oven ready for removal and installation of the guides, I would not be surprised if the mechanic was trying to drive the guides in and out of this head cold:
    DSC03735.jpg


    Here is what happens if you use the wrong tool for the job, little bit of a tear, if you don't have the right tools and have no idea what you are doing please leave it alone:
    DSC03740.jpg
    Classic Honda 50's Australia - Visit our online store at -Hidden Content

    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.

  2. #2
    Forum Founder Classic Honda 50's's Avatar
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    Here are the correct valve guide removal and installation tools for the job from Honda:
    DSC03781.jpg


    The correct tool positively locates in the guide to stop it from moving around causing damage to the head:
    DSC03783.jpg


    Valve guide tool installed in the guide ready to go:
    DSC03784.jpg


    Here is what I suspect the mechanic used on this head, good old all over the place pin punch:
    DSC03793.jpg


    Here is the valve guide installation tool:
    DSC03795.jpg


    Positively located on the guide ready for installation:
    DSC03800.jpg


    It is extremely important to check the size of the old and new guides to make sure that they are the same size, have seen a few high dollar heads cracked from too big a diameter replacement guides:

    Old Inlet Guide:
    DSC03749.jpg


    New Inlet Guide:
    DSC03751.jpg


    Old Exhaust Guide:
    DSC03752.jpg


    New Exhaust Guide:
    DSC03753.jpg
    Classic Honda 50's Australia - Visit our online store at -Hidden Content

    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.

  3. #3
    Forum Founder Classic Honda 50's's Avatar
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    Head is now clean, inspected, repaired, lubricated and assembled ready to be installed:
    Dsc03755 S.jpg


    Dsc03758 S.jpg


    Dsc03761 S.jpg


    Dsc03763 S.jpg


    Dsc03765 S.jpg


    DSC03772.jpg


    Ready to send home with new guides reamed to the correct size in the lathe, honed finish for the guides with a Flexhone when installed, valve seats recut, fully lubricated with TRW cam and engine assembly lube with cam installed:
    Dsc03802 S.jpg


    If you are going to work on your own cylinder head remember to thoroughly clean it before you start, carefully inspect the cylinder head and gasket faces for cracks or damage, remove the carbon from the exhaust guide before removing the guide from the head, heat the head to the correct temperature before removing and installing the guides, use the correct tools to get the job done without damaging the head.

    Please note that this is not a guide on how to recondition a cylinder head as there are a few steps of the process left out
    Classic Honda 50's Australia - Visit our online store at -Hidden Content

    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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