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DT125R FORUM

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  4. engine piston check

engine piston check

Scheduled Pinned Locked Moved Engine
73 Posts 6 Posters 6.8k Views 1 Watching
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  • S SpookDog

    @erion1

    Bud! I’m guessing that the ‘scratch marks’ are spaced around the piston in 4 places?
    This is because you reused a head gasket (worst 15 £-€ you never spent!) It’s called a 4 point heat seizure. If you look up inside of the piston, the inside of the crown will be black and scorched from the heat seizure. Whether you saw it on the temp gauge or not; it overheated…

    Other thing is the piston shouldn’t ‘click’ back and forwards if it’s the right size. Neither should you have that amount of blow by past the rings! I think that the person who did your rebore may of done you wrong…

    I’ve used old bits to keep me on the road, but never as an end plan! Even then I rode it like a grandad, never above 5-6K max, never like a ‘yoof’…

    What country are you in? Somebody might be able to recommend a good motorcycle engineer to help you move forwards…
    You’re going to have to put in a proper fitting piston. Why quibble about a rebore?…
    If you want to ride and enjoy your bike to the max. Just fix it please!…

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    erion1
    wrote on last edited by
    #34
    This post is deleted!
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      erion1
      wrote on last edited by
      #35

      hey @SpookDog i was wondering if what happened could cause my crank bearing go bad as someone told me that, is there any way i can check that, i was thinkit that the water that got in caused corrosion on the bearing or something, i just don't want my engine to go boom haha

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      • E erion1

        hey @SpookDog i was wondering if what happened could cause my crank bearing go bad as someone told me that, is there any way i can check that, i was thinkit that the water that got in caused corrosion on the bearing or something, i just don't want my engine to go boom haha

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        SpookDog
        wrote on last edited by SpookDog
        #36

        @erion1

        What are the first 5 letters and numbers stamped into your frame (headstock) and engine block? (above clutch arm) …

        The crank would rumble when you spin it, and feel ‘notchy’ if it was corroded or damaged.
        Also with ‘normal’ wear the stator could be moved, it’d click slightly when gently shimmied with a flathead screwdriver. Or even by hand depending on how bad it is…
        I’d be more worried about you crank if it’s as bad as you say!…

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        • S SpookDog

          @erion1

          What are the first 5 letters and numbers stamped into your frame (headstock) and engine block? (above clutch arm) …

          The crank would rumble when you spin it, and feel ‘notchy’ if it was corroded or damaged.
          Also with ‘normal’ wear the stator could be moved, it’d click slightly when gently shimmied with a flathead screwdriver. Or even by hand depending on how bad it is…
          I’d be more worried about you crank if it’s as bad as you say!…

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          erion1
          wrote on last edited by
          #37

          @SpookDog i checked for play when i had it apart it was perfect no up down play slight side to side which is normal and as the bike drank my water before i was thinking it could have litle bit of water in the crank so yesterday i put some 2t oil on the tank for more lubrication on the crank and let it run for a bit so it gets lubed up and maybe prevent corrosion if it didn't happen already

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          • S SpookDog

            @erion1

            What are the first 5 letters and numbers stamped into your frame (headstock) and engine block? (above clutch arm) …

            The crank would rumble when you spin it, and feel ‘notchy’ if it was corroded or damaged.
            Also with ‘normal’ wear the stator could be moved, it’d click slightly when gently shimmied with a flathead screwdriver. Or even by hand depending on how bad it is…
            I’d be more worried about you crank if it’s as bad as you say!…

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            erion1
            wrote on last edited by
            #38

            @SpookDog so you're saying i can rotate the stator if the crank is good, do you mean rotate with hand or with what, and can you explain a bit more what you mean by it would click when shimed with a screwdriver

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            • E erion1

              @SpookDog so you're saying i can rotate the stator if the crank is good, do you mean rotate with hand or with what, and can you explain a bit more what you mean by it would click when shimed with a screwdriver

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              SpookDog
              wrote on last edited by
              #39

              @erion1

              You still have the barrel off yeah?
              You should be able to rotate the stator easily by hand. It shouldn’t make any rumble noises or feel clicky/notchy when you turn it…

              If you gently lever the stator up and down it shouldn’t have any free movement. It might flex a bit if levered too much…

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              • S SpookDog

                @erion1

                You still have the barrel off yeah?
                You should be able to rotate the stator easily by hand. It shouldn’t make any rumble noises or feel clicky/notchy when you turn it…

                If you gently lever the stator up and down it shouldn’t have any free movement. It might flex a bit if levered too much…

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                erion1
                wrote on last edited by
                #40

                @SpookDog no i put everything together as i needed space in my garage and had no place to put the parts and im not runing the bike either so its gona be like that for a month as i don't got the money for the new stuf rn but i'll take it apart again to check that then, but that what you told me is to check the crank bearings right? not the rod bearing it could be good if i can check both of them if they are in good condition without spliting the cases
                Thanks for the info!

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                • S SpookDog

                  @erion1

                  You still have the barrel off yeah?
                  You should be able to rotate the stator easily by hand. It shouldn’t make any rumble noises or feel clicky/notchy when you turn it…

                  If you gently lever the stator up and down it shouldn’t have any free movement. It might flex a bit if levered too much…

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                  erion1
                  wrote on last edited by
                  #41

                  @SpookDog i did what you said but i didn't take the cylinder off i only took the sparkplug and took the stator side cover off,
                  it could be easily turned by hand and it has no movement up or down neither side to side no clicking no nothing just a little friction noisse wich i think is coming from the piston as its not in a good condition

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                  • E erion1

                    @SpookDog i did what you said but i didn't take the cylinder off i only took the sparkplug and took the stator side cover off,
                    it could be easily turned by hand and it has no movement up or down neither side to side no clicking no nothing just a little friction noisse wich i think is coming from the piston as its not in a good condition

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                    SpookDog
                    wrote on last edited by
                    #42

                    @erion1

                    Bit of piston ‘scoosh’ is to expected in that condition 🙂

                    The crank turned real smoothly as well? No little stops or notchyness?

                    Bud! What are the first 3 numerics after the * on your engine and frame? If you let us know we can find out what year and model you have. It’s especially important when it comes to electrics…

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                    • MadGyverM Offline
                      MadGyverM Offline
                      MadGyver
                      wrote on last edited by
                      #43

                      @erion1 If you have the original brake hoses,they say manufacture date,99% of the time it's the same year the bike came out of the factory. So with the first 3 alphanumeric's that @SpookDog said and the year of the hose you have the model/year of the bike

                      I need my tools and a pile of junk.....

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                      • S SpookDog

                        @erion1

                        Bit of piston ‘scoosh’ is to expected in that condition 🙂

                        The crank turned real smoothly as well? No little stops or notchyness?

                        Bud! What are the first 3 numerics after the * on your engine and frame? If you let us know we can find out what year and model you have. It’s especially important when it comes to electrics…

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                        erion1
                        wrote on last edited by
                        #44

                        @SpookDog yeah it was smooth only when the piston was going up it got harder to rotate from little bit of compresion as i didn't remove the whole cylinder out,
                        the frame is a 4DK-006706 the engine is the same

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                        • MadGyverM MadGyver

                          @erion1 If you have the original brake hoses,they say manufacture date,99% of the time it's the same year the bike came out of the factory. So with the first 3 alphanumeric's that @SpookDog said and the year of the hose you have the model/year of the bike

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                          erion1
                          wrote on last edited by erion1
                          #45

                          @MadGyver on the front brake hose it is repeated many times it writes DOT NCRN 12/91 1/8 HL im guessing that 12/91 refers to december 1991 maybe ?

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                          • E erion1

                            @MadGyver on the front brake hose it is repeated many times it writes DOT NCRN 12/91 1/8 HL im guessing that 12/91 refers to december 1991 maybe ?

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                            SpookDog
                            wrote on last edited by
                            #46

                            @erion1

                            That would tie in right. You have the 3 wire servo fitted to your bike don’t you?…
                            So it’s pre- 96 I think…

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                            • S SpookDog

                              @erion1

                              That would tie in right. You have the 3 wire servo fitted to your bike don’t you?…
                              So it’s pre- 96 I think…

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                              erion1
                              wrote on last edited by
                              #47

                              @SpookDog yeah its a 3wire

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                              • S SpookDog

                                @erion1

                                That would tie in right. You have the 3 wire servo fitted to your bike don’t you?…
                                So it’s pre- 96 I think…

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                                erion1
                                wrote on last edited by
                                #48

                                @SpookDog i got a top end athena gasket kit but since i have to rebore to 57mm bore will it be a problem ?

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                                • E erion1

                                  @SpookDog i got a top end athena gasket kit but since i have to rebore to 57mm bore will it be a problem ?

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                                  SpookDog
                                  wrote on last edited by SpookDog
                                  #49

                                  @erion1

                                  No, I have a 58 I use (about 140cc)

                                  You do have to check it doesn’t touch the power valve when it gets to a certain size…

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                                  • S SpookDog

                                    @erion1

                                    No, I have a 58 I use (about 140cc)

                                    You do have to check it doesn’t touch the power valve when it gets to a certain size…

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                                    erion1
                                    wrote on last edited by
                                    #50

                                    @SpookDog yeah i know about power valve, i was just thinking would the top end gasket be smaller than the barrel but it should be fine

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                                    • E erion1

                                      @SpookDog yeah i know about power valve, i was just thinking would the top end gasket be smaller than the barrel but it should be fine

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                                      SpookDog
                                      wrote on last edited by
                                      #51

                                      @erion1

                                      It will be…

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                                      • S SpookDog

                                        @erion1

                                        It will be…

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                                        erion1
                                        wrote on last edited by
                                        #52

                                        @SpookDog yo one last thing i made a video today of kicking the bike over just so you can hear the bike make that friction noise to know if the crank is good, idk maybe just my stress is making me hear it or idk here is the vid https://imgur.com/gallery/HRIy3mb

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                                        • E erion1

                                          @SpookDog yo one last thing i made a video today of kicking the bike over just so you can hear the bike make that friction noise to know if the crank is good, idk maybe just my stress is making me hear it or idk here is the vid https://imgur.com/gallery/HRIy3mb

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                                          SpookDog
                                          wrote on last edited by
                                          #53

                                          @erion1

                                          Can’t hear anything over the exhaust! You’ll have to do it turning the stator by hand…

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