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  • valve assembly query

    ok came up to my first setback today.
    (im putting it down to rookie mistake)
    finally got the Z50 running again today after pulling the top end off due to oil and smoke going everywhere. now instead of getting a gasket pack i thought id cut out some cork ones and reuse the cylinder head gasket as it looked pretty good. Surprise Surprise the old gasket hasnt sealed and i have to do it all over again. Will be ordering the
    pack tonight.
    1st question. when i had the cylinder head off i took out the valves to have a look see (im a virgin at this so couldnt help myself). when i removed the valves i paid attention to the order of things and the small rubber o-ring was above the inlet and exhaust valve guides, where as in my genuine parts book the rubber o-ring is beneath the guides. where should the o-rings be?

    also i believe that the valve stem seal and cap was missing off of the exhaust valve , could this be a possible source of oil in the exhaust?

    2nd what model was between the Z50a and K2 as that is where my model numbers fall. i assume its a K1 but couldnt find it in the id chart

    Thanks Anthony

  • #2
    Hi Anthony

    I tried to use cork base gaskets on a VW buggy engine 30 years ago to lift the rings off the massive lip in the bore but the cork does not compress well under a cylinder, have reused head gaskets out of desperation but need to coat them in a gasket sealant to have any chance of the head gasket sealing correctly.

    There is an O ring under the intake and exhaust guide part No 17, typically only the exhaust valve guide has a valve stem seal part No 8 held by the valve stem cap part No 9, the inlet valve guide is tapered at the top to help divert oil from entering the guide and does not have a valve stem seal.

    Valve Fiche.gif

    If your inlet/exhaust guides or valve stems are worn they will allow oil to be sucked into the intake or out the exhaust resulting in your engine smoking, I have sponsored and built quite a few race bike engines over the years and on a few motors have not run valve stem seals at all but only on new assemblies.

    Typically when the valve stem seal starts to fail you will get a puff of white smoke for a bit at start up on a cold engine then it will reduce or stop as the engine heats up and the engine components expand. If the guides are worn out you can get a continuous stream of smoke out the exhaust.

    If the bike is hard to start and the kickstart arm moves easily (Low Compression) you may have worn rings which will cause continuous smoking, can typically see a constant stream of blue/black smoke from the exhaust from burning oil blowing past the rings into the combustion chamber.

    The Z50A Hard-tail models were the Z50AK0, Z50AK1 and Z50AK2, the date stamp for your bike is on the inside of the left rear axle plate on the frame:

    https://www.classichonda50saustralia...-%201.59MB.pdf

    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.

    Comment


    • #3
      thanks Jamie for the great info. I've ordered a gasket kit plus the stem seal and cap. will move the o-rings when i get it apart again.
      also is it worth putting gasket goo on new seals.

      when I first got the bike running there was as much oil coming out of the muffler as anywhere else so hopefully when i get it running again I'll know more...

      Comment


      • #4
        I have purchased quite a few Z50's that have had a heap of oil in the exhaust from owners trying to stop them rusting during storage.

        If you have new gaskets and flat mating surfaces the new gaskets will install ok dry, I always use Hylomar Blue Aerosol gasket goo on most gaskets, just a thin even film let it tack dry then install.

        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.

        Comment


        • #5
          hi again.
          got the seal kit yesterday so took it apart again and put together again and... i got it started again. so proud of myself.
          so now I have a few more issues...
          still smoke coming out of the muffler so could be rings.
          the bike still has no power in 3rd gear so I fiddled with the carbi didn't help although didn't really know what I was doing . is there a good video on carbis anywhere I havnt found one yet. will be searching more tonight.
          also not happy with fuel supply will post pic any idea on how to get the flow better would be appreciated.
          one last issue I've found is that the bolt holes connecting the carbi have mostly been stripped, I've installed longer bolts but don't feel confident tightening them up to spec.
          oh I also get a backfire every now and again, carbi setting?
          20200519_154548.jpgany assistance would be greatly appreciated.

          Comment


          • #6
            Need to get a heat insulator between the head and inlet manifold to reduce the heat going into the intake manifold, check for any intake air leaks or a leaking exhaust gasket at the head, with the stock engine and carb keep the jetting and settings stock and make sure the carb is clean - looks like a new carb what type is it?

            Have you tried to run without the air filter, have had a few customers have issues with that style of Red mesh air filter recently, very restrictive if it is the same type.

            Can't see in the pic, does the bolt go through the inlet manifold/insulator/carb to a nut on the carb?

            Is there rust in the tank, if you take the fuel hose off the carb is there decent flow in the fuel tap on position?

            Have you checked the points gap/ignition timing?

            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.

            Comment


            • #7
              thanks again Jaimie
              this is turning into a huge learning curve/opportunity for me so sorry if im asking too many questions, just trying to get my head around it.
              there is rust in the tank still but fuel seemed to run freely. have tried loosening with nuts and bolts and vinigar. it still needs work but trying to get the thing running for the kids .do you recommend sealing the tank with something?

              may of been a small air leak at exhaust gasket. how would this affect it? (nothing compared to the leak going into the muffler though as its missing the packing, still working on that one as well)

              it is a new carbi purchased before getting onto the forum dont know what type though. ill see if i can put the original spacer in. have the original carbi for it that im still trying to fix up, could not clear the drain hole in it. turns out someone(probably my old man jammed a piece of wood up it to stop it leaking, worked a treat)now i need to go find an o ring to fit to keep the fuel in again..
              pretty sure points and timing were right but will recheck as im awaiting a new piston and rings and ive pulled it all apart AGAIN.
              the bolts go through the inlet manifold/carbi and into a retained nut.
              the almost stripped bolt holes i was referring to are connecting inlet manifold to the head. so in the head.

              Thanks
              Ant

              Comment


              • #8
                Hi Ant

                The only stupid question is the one not asked.

                I have half a cup of steering bearings that I put in the fuel tank with a cup of kerosene and a cap of motor oil, shake the tanks till your arms ache have a rest and do it a few more times till you get rid of the flakey rust then run an inline fuel filter. With the tank liner if you need it you need it, I am not a big fan of tank liners but am about to do a J1 tank with the POR15 kit.

                With a leaking exhaust gasket the engine can crackle and pop, not so much of a problem with the muffler packing which is more messy than anything.

                Set the carb at 1.5 turns out on the air screw with the needle in the middle clip position as a starting point and adjust to suit what your engine needs, here is a carb cleaning video on YouTube:



                Need to get a bottoming tap to see if you can correct/straighten the threads in the head so you can tension the intake manifold. If the thread is stuffed can repair it with a helicoil.

                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.

                Comment


                • #9
                  wow
                  a Helicoil never new these things existed. you just changed my life. so simple an idea, just brilliant
                  thx

                  Comment


                  • #10
                    ok i put in a couple of helicoils the other day while waiting for a set of rings to arrive, simple as. now bike is back together and up and running, no more smoke and plenty more power. thanks for all your help Jaimie.
                    Still got a few issues like the fuel line. but after taking the petcock off, i found a few flakes of rust that may mave been slowing fuel rate down, so ordered one of the right angled ones with a filter to replace it and try streamline the flow of fuel (dont know if that will make a difference but will make me feel better)

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