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DT125R FORUM

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  4. Athena 170

Athena 170

Scheduled Pinned Locked Moved Top End
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  • B Bananper

    @calum so basically you lose some peak power in exchange for mid range power? Correct me if I'm wrong 🤓

    CalumC Online
    CalumC Online
    Calum
    wrote on last edited by
    #98

    @bananper Without a Dyno Graph it's hard to tell. But due to the port timings being way out, once you start climbing through the revs, the opportunity for the power to be made starts diminishing.

    Hence why at low RPM's you have the extra CC's to help deliver more low down grunt, but the power tapers off and the gap between a stock barrel and Athena barrel starts to thin out. You definitely lose overrev with the big bore, so the stock barrel will continue to rev out further, allow you to zap out a few extra ponies with the help of porting.

    Two strokes in general don't love over square engines, the fact that the big bore kit widens the bore whilst maintaining the stroke exacerbates this. A longer stroke is ideal for this kit. There is the potential then, for the longer stroke to correct the port timings, out by 3mm I'm led to believe, to actually correct the issues with the barrel.

    But by the time you've done all that, you may as well have just thrown a 3XP0 cylinder and crank and be done with it.

    I haven't the expertise or experience to really comment on how any of this translates. But it's just what I've read from various sites.

    Always Originate, Never Pirate!

    B 1 Reply Last reply
    1
    • CalumC Calum

      @bananper Without a Dyno Graph it's hard to tell. But due to the port timings being way out, once you start climbing through the revs, the opportunity for the power to be made starts diminishing.

      Hence why at low RPM's you have the extra CC's to help deliver more low down grunt, but the power tapers off and the gap between a stock barrel and Athena barrel starts to thin out. You definitely lose overrev with the big bore, so the stock barrel will continue to rev out further, allow you to zap out a few extra ponies with the help of porting.

      Two strokes in general don't love over square engines, the fact that the big bore kit widens the bore whilst maintaining the stroke exacerbates this. A longer stroke is ideal for this kit. There is the potential then, for the longer stroke to correct the port timings, out by 3mm I'm led to believe, to actually correct the issues with the barrel.

      But by the time you've done all that, you may as well have just thrown a 3XP0 cylinder and crank and be done with it.

      I haven't the expertise or experience to really comment on how any of this translates. But it's just what I've read from various sites.

      B Offline
      B Offline
      Bananper
      wrote on last edited by
      #99

      @calum 3XP0 is wr200 engine right?

      CalumC 1 Reply Last reply
      0
      • B Bananper

        @calum 3XP0 is wr200 engine right?

        CalumC Online
        CalumC Online
        Calum
        wrote on last edited by
        #100

        @bananper DT200R I think.

        Always Originate, Never Pirate!

        B 1 Reply Last reply
        0
        • CalumC Calum

          @bananper DT200R I think.

          B Offline
          B Offline
          Bananper
          wrote on last edited by
          #101

          @calum is there any difference between wr200 and the dt200?

          CalumC 1 Reply Last reply
          0
          • B Bananper

            @calum is there any difference between wr200 and the dt200?

            CalumC Online
            CalumC Online
            Calum
            wrote on last edited by
            #102

            @bananper wr is a competition bike.

            Always Originate, Never Pirate!

            1 Reply Last reply
            1
            • Louis-DT-WRL Offline
              Louis-DT-WRL Offline
              Louis-DT-WR
              wrote on last edited by
              #103

              I believe the dt200r is a 3ET barrel. Dt200wr and wr200 share the same 3xp cylinder which is nickasil plated but you can buy steel sleeves for them. I believe the dt200wr is autolube and has a tachometer at generator different dor the electrics

              Also the dt230 cylinder and crank is a possibility 🤑 never seen this one done.

              1 Reply Last reply
              1
              • 2 Offline
                2 Offline
                2stroketerry
                wrote on last edited by
                #104

                Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha

                declanD Louis-DT-WRL 2 Replies Last reply
                2
                • 2 2stroketerry

                  Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha

                  declanD Offline
                  declanD Offline
                  declan
                  wrote on last edited by
                  #105

                  @2stroketerry very cool I love all the little Frankenstein things you can do to engines

                  1 Reply Last reply
                  0
                  • 2 Offline
                    2 Offline
                    2stroketerry
                    wrote on last edited by
                    #106

                    Wossner do a forged piston kit for the dt 125 that is 61mm and the absolute maximum can bore a dt barrel to. Gives around 146cc. https://www.ebay.co.uk/itm/Wossner-Piston-Kit-KTM-LC2-1991-2006-Yamaha-DT125-Over-Bore-61mm/371410153446?hash=item5679c52fe6:g:YI8AAOSwHnFVyn8J
                    0_1527803968517_mqr4k2wj 160cc.jpg

                    declanD 1 Reply Last reply
                    2
                    • 2 2stroketerry

                      Wossner do a forged piston kit for the dt 125 that is 61mm and the absolute maximum can bore a dt barrel to. Gives around 146cc. https://www.ebay.co.uk/itm/Wossner-Piston-Kit-KTM-LC2-1991-2006-Yamaha-DT125-Over-Bore-61mm/371410153446?hash=item5679c52fe6:g:YI8AAOSwHnFVyn8J
                      0_1527803968517_mqr4k2wj 160cc.jpg

                      declanD Offline
                      declanD Offline
                      declan
                      wrote on last edited by
                      #107

                      @2stroketerry what gains should I expect from doing the overbore and porting

                      1 Reply Last reply
                      0
                      • 2 Offline
                        2 Offline
                        2stroketerry
                        wrote on last edited by
                        #108

                        Hi, If you get Karl at Kpmotosolutions to re-sleeve the cylinder to 66mm to suit Forged Wiseco blaster piston and machine the head to new bore size and alter squish and compression to suit. He will also fully port the re-sleeved barrel to suit your driving style, some people want a really high reving max horsepower top end like a YZ 125 for example. He can also bore out the standard Mikuni 28 TM carb to 30mm but will need to enlarge your inlet manifold to 30mm and sort your own jetting out.
                        With the price of the forged piston kit, Karl re-sleeving and porting the barrel and head plus the price for boring out the carb, it will all add up to less than the Athena 170cc kit. When bored out to suit 66mm Wiseco piston the engine will be 176cc.
                        With a decent exhaust on it will be over 30 bhp at the rear wheel, have to fit set of stronger clutch springs too. With all the mods done and the carb setup spot on will do 115 mph and wheelie in every gear. http://www.kpmotosolutions.com/

                        1 Reply Last reply
                        1
                        • 2 2stroketerry

                          Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha

                          Louis-DT-WRL Offline
                          Louis-DT-WRL Offline
                          Louis-DT-WR
                          wrote on last edited by
                          #109

                          @2stroketerry said in Athena 170:

                          Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha

                          Do the windows in the skirt effect it? The blaster 200 isn't crank induction I think

                          1 Reply Last reply
                          0
                          • 2 Offline
                            2 Offline
                            2stroketerry
                            wrote on last edited by
                            #110

                            Hi @Louis-James . no the windoes in the skirt don't matter and don,t affect the running at all even though dt has case induction, if anthing add slightly to the power as some 2 stroke tuners add windows to piston skirts. Strenth wise pistons are ok too
                            with windows in the skirt and being forged makes them a lot stronger than cast pistons, also a superior alloy is used in forged pistons.

                            1 Reply Last reply
                            0
                            • Louis-DT-WRL Offline
                              Louis-DT-WRL Offline
                              Louis-DT-WR
                              wrote on last edited by
                              #111

                              So what's the crack with the 3bn cylinders and the tzr 2RH?

                              Been a while since talking about 125 cylinders I need a refresher.
                              How many different genuine Yamaha cylinders fit the DT?

                              Does the one of the tzr 250 cylinders fit?

                              CalumC 1 Reply Last reply
                              0
                              • Louis-DT-WRL Louis-DT-WR

                                So what's the crack with the 3bn cylinders and the tzr 2RH?

                                Been a while since talking about 125 cylinders I need a refresher.
                                How many different genuine Yamaha cylinders fit the DT?

                                Does the one of the tzr 250 cylinders fit?

                                CalumC Online
                                CalumC Online
                                Calum
                                wrote on last edited by
                                #112

                                @louis-james Don't know about TZR cylinders.

                                But

                                3MB
                                3MBP
                                4FU
                                Are bolt ons.

                                The 3BN has a slightly bigger bore, so shorter stroke, as a result, a 3MB con rod will bit too long.

                                Always Originate, Never Pirate!

                                1 Reply Last reply
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