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DT125R FORUM

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  4. ‘Drivetrain Slap’?

‘Drivetrain Slap’?

Scheduled Pinned Locked Moved Suspension
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  • Stevie WonderS Offline
    Stevie WonderS Offline
    Stevie Wonder
    wrote on last edited by
    #3

    Is it possible your chains stretched in one place causing a tight and loose spot.

    Riding BMX you get this happen a lot stopping you from being able to get the correct slack. This only ever happens with cheap / non genuine or chains made by a non reputable maker

    Obviously I know this is bmx so I’m not sure how well it carries over but I guess the same principle could get applied

    1 Reply Last reply
    1
    • S SpookDog

      Does everyone else suffer from drive chain slack when throttling up and down while in gear?...
      I keep my chain (x ring) lubed and adjusted properly, yet I still get a lot of play when throttling up or down in gear. Is this just inherent from the long chain length? It’s annoyingly ‘snatchy’. Is there any aftermarket sprung chain roller available?...

      HOTSHOT IIIH Offline
      HOTSHOT IIIH Offline
      HOTSHOT III
      wrote on last edited by
      #4

      @SpookDog Cheap chains can cause this as others have said but sounds like you've pushed the boat out running an X-ring chain.

      There's a chance your lower chain roller could be fitted upside down; it's by no means obvious and I've seen lots of people fall down this hole on the DTR, it allows the chain to hit the frame's cross member below the swingarm pivot and could also increase its propensity to hit the lower part of the rear chain guide, particularly whilst decelerating.

      Spring-loaded chain rollers/slippers were a thing on late 70s/early 80s trials and MX bikes but the pad or roller will wear quickly and running one could cause problems on a bike with as much rear travel as the DTR as chain tension varies so much over the suspension movement.

      Chain roller bracket should look like this

      alt text

      S 1 Reply Last reply
      1
      • HOTSHOT IIIH HOTSHOT III

        @SpookDog Cheap chains can cause this as others have said but sounds like you've pushed the boat out running an X-ring chain.

        There's a chance your lower chain roller could be fitted upside down; it's by no means obvious and I've seen lots of people fall down this hole on the DTR, it allows the chain to hit the frame's cross member below the swingarm pivot and could also increase its propensity to hit the lower part of the rear chain guide, particularly whilst decelerating.

        Spring-loaded chain rollers/slippers were a thing on late 70s/early 80s trials and MX bikes but the pad or roller will wear quickly and running one could cause problems on a bike with as much rear travel as the DTR as chain tension varies so much over the suspension movement.

        Chain roller bracket should look like this

        alt text

        S Offline
        S Offline
        SpookDog
        wrote on last edited by
        #5

        @HOTSHOT-III

        Yeah, I fitted a JT sprocket & X~ring chain set. It’s a great chain. My roller does look a bit worn down compared to your pic. I’ll try replacing it and tweaking the chain again when I fit my new back tire...

        Can anyone please link me to a good replacement roller?...

        CalumC 1 Reply Last reply
        0
        • S SpookDog

          @HOTSHOT-III

          Yeah, I fitted a JT sprocket & X~ring chain set. It’s a great chain. My roller does look a bit worn down compared to your pic. I’ll try replacing it and tweaking the chain again when I fit my new back tire...

          Can anyone please link me to a good replacement roller?...

          CalumC Offline
          CalumC Offline
          Calum
          wrote on last edited by
          #6

          @SpookDog said in ‘Drivetrain Slap’?:

          @HOTSHOT-III
          Can anyone please link me to a good replacement roller?...

          Ditto, one ony ETX looks goosed 😕

          Always Originate, Never Pirate!

          S 1 Reply Last reply
          0
          • CalumC Calum

            @SpookDog said in ‘Drivetrain Slap’?:

            @HOTSHOT-III
            Can anyone please link me to a good replacement roller?...

            Ditto, one ony ETX looks goosed 😕

            S Offline
            S Offline
            SpookDog
            wrote on last edited by
            #7

            Also my top roller looks like it has never been touched by the chain. Is it there for when the swing arm is at maximum compression? It looks to high up for any normal use...

            HOTSHOT IIIH 1 Reply Last reply
            0
            • S SpookDog

              Also my top roller looks like it has never been touched by the chain. Is it there for when the swing arm is at maximum compression? It looks to high up for any normal use...

              HOTSHOT IIIH Offline
              HOTSHOT IIIH Offline
              HOTSHOT III
              wrote on last edited by HOTSHOT III
              #8

              @SpookDog I've always just used genuine ones from Fowlers or Yambits. Worth replacing the plastic sleeve as well. They seem to last pretty well if you degrease and re-lube them when washing the bike or a dash of chain lube whenever you lube the chain.

              A lot of MX shops sell aftermarket ballraced chain rollers (basically skateboard wheels) so just a matter of getting one with a 12mm ID the correct width. DirtBikeExpress have a fair selection:

              https://www.dirtbikexpress.co.uk/search.php?search=chain+rollers

              Yes my top one hardly ever displays signs of use, it's only there to stop the chain slicing through the airbox when the rear suspension is on full compression as you say. In fact when that pic was taken, I'd just swapped the top and bottom rollers as a temporary measure as we were in lockdown! The lower one does a lot more work in normal riding conditions

              S 1 Reply Last reply
              0
              • HOTSHOT IIIH HOTSHOT III

                @SpookDog I've always just used genuine ones from Fowlers or Yambits. Worth replacing the plastic sleeve as well. They seem to last pretty well if you degrease and re-lube them when washing the bike or a dash of chain lube whenever you lube the chain.

                A lot of MX shops sell aftermarket ballraced chain rollers (basically skateboard wheels) so just a matter of getting one with a 12mm ID the correct width. DirtBikeExpress have a fair selection:

                https://www.dirtbikexpress.co.uk/search.php?search=chain+rollers

                Yes my top one hardly ever displays signs of use, it's only there to stop the chain slicing through the airbox when the rear suspension is on full compression as you say. In fact when that pic was taken, I'd just swapped the top and bottom rollers as a temporary measure as we were in lockdown! The lower one does a lot more work in normal riding conditions

                S Offline
                S Offline
                SpookDog
                wrote on last edited by
                #9

                @HOTSHOT-III
                Cheers, I would much rather have a ball or needle raced roller...

                If anyone can recommend a good one I’d be grateful. Save me my usually painful learning curve 😜 ...

                Cheers!

                S 1 Reply Last reply
                0
                • S SpookDog

                  @HOTSHOT-III
                  Cheers, I would much rather have a ball or needle raced roller...

                  If anyone can recommend a good one I’d be grateful. Save me my usually painful learning curve 😜 ...

                  Cheers!

                  S Offline
                  S Offline
                  SpookDog
                  wrote on last edited by SpookDog
                  #10

                  Even just the dimensions of the roller I anyone knows it offhand...

                  Also, I’ve searched every where and can’t find any progressive fork springs for an early DTR125. Has anyone got a link or info for them please?...

                  HOTSHOT IIIH 1 Reply Last reply
                  0
                  • S SpookDog

                    Even just the dimensions of the roller I anyone knows it offhand...

                    Also, I’ve searched every where and can’t find any progressive fork springs for an early DTR125. Has anyone got a link or info for them please?...

                    HOTSHOT IIIH Offline
                    HOTSHOT IIIH Offline
                    HOTSHOT III
                    wrote on last edited by
                    #11

                    @SpookDog Just measured some NIP genuine parts:

                    Plastic sleeve
                    Overall length 28mm
                    ID 12mm
                    OD 18mm where the roller fits (25mm) 24mm at the "top hat brim" part which is 3mm deep

                    Foam roller
                    Overall length 24mm
                    ID 18mm
                    OD 35mm

                    A lot of the ballraced aftermarket rollers look like they're designed to be fitted directly to the frame mount using an M8 bolt (although they don't give dimensions which seems a pretty basic oversight for someone selling universal MX bike parts online); potentially not a problem for the upper DTR roller but to use one as a lower one would necessitate either butchering the stock bracket which bolts to the frame or designing and making a new one

                    S 1 Reply Last reply
                    1
                    • HOTSHOT IIIH HOTSHOT III

                      @SpookDog Just measured some NIP genuine parts:

                      Plastic sleeve
                      Overall length 28mm
                      ID 12mm
                      OD 18mm where the roller fits (25mm) 24mm at the "top hat brim" part which is 3mm deep

                      Foam roller
                      Overall length 24mm
                      ID 18mm
                      OD 35mm

                      A lot of the ballraced aftermarket rollers look like they're designed to be fitted directly to the frame mount using an M8 bolt (although they don't give dimensions which seems a pretty basic oversight for someone selling universal MX bike parts online); potentially not a problem for the upper DTR roller but to use one as a lower one would necessitate either butchering the stock bracket which bolts to the frame or designing and making a new one

                      S Offline
                      S Offline
                      SpookDog
                      wrote on last edited by SpookDog
                      #12

                      @HOTSHOT-III

                      Cheers for the info bud! I did manage to find a few likely suspects. 8mm inner hole and fittable to the nut on my lower mount, as well as being bearing raced. I’ve even found a few spring loaded contraptions that look fitable,(with a bit of finessing!) but I imagine that if they’re in constant contact with the chain that they’d shred the roller PDQ! It’s all food for thought though 😉 ...
                      Once I tap a grease nipple into both sides of the swing arm front mount points. Try and find some half decent progressive front springs, get the upper and lower bushes and new seals, I’ll be happy. Have managed to get hold of a dtr200 variable dampening rear shock that I want to try and rebuild as well. I’ll have more faith in the setup at 70mph plus speeds 🤞 ...

                      I also want to improve the engine mount bolts under the swing arm bolt and at the engine front mount below the exhaust and bottom coolant pipe...

                      I think my engine may of been shifting about under loads and putting excess pressure on the cylinder head mount. Maybe affecting the gasket seal??!... on

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