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DT125R FORUM

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  4. DT 125 Cylinder head and piston rings questions

DT 125 Cylinder head and piston rings questions

Scheduled Pinned Locked Moved Engine
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  • Glynn123G Offline
    Glynn123G Offline
    Glynn123
    wrote on last edited by
    #1

    Last weekend I got the Facebook marketplace steal of the year, a nearly brand new DTR engine with kickstart, carb, pv servo and a few other little goodies thrown in. Drove the 200 mile round trip to get it and was amazed what was under the dust, this things never been stripped or broken apart in any way, the carburetors litterally new and unseized too! Shame I've just got my Polini 32 working well.
    I pulled the barrel off leaving the head intact to check ring gaps and head type, rings we're stuck from plug being out and slight moisture, but once freed the piston and bore looked brand new, no scores at all.
    Ring gaps sitting at 19 thou, as far as I'm aware this is out of spec, what's the best rings out there to fit a standard bore Yamaha piston? And is there really a great power loss with the ridged cylinder head? (Think the engines an 03?) I could strip the unrestricted head off my old engine which is already skimmed but I don't really want to disturb the head gasket if there's not too much power loss?
    Cheers

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    • CalumC Online
      CalumC Online
      Calum
      wrote on last edited by
      #2

      Something like 80% of the power is made at the head.

      So yes, a restrictive head will dramatically affect the power.

      Always Originate, Never Pirate!

      Glynn123G 1 Reply Last reply
      0
      • CalumC Calum

        Something like 80% of the power is made at the head.

        So yes, a restrictive head will dramatically affect the power.

        Glynn123G Offline
        Glynn123G Offline
        Glynn123
        wrote on last edited by
        #3

        I'm more thinking of how resitrictive is this head in comparison to the other DT ones?

        CalumC DanRacingD 2 Replies Last reply
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        • Glynn123G Glynn123

          I'm more thinking of how resitrictive is this head in comparison to the other DT ones?

          CalumC Online
          CalumC Online
          Calum
          wrote on last edited by
          #4

          @Glynn123 Yeah, pretty restrictive. People say how noticeable it is.

          Always Originate, Never Pirate!

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          • Glynn123G Glynn123

            I'm more thinking of how resitrictive is this head in comparison to the other DT ones?

            DanRacingD Offline
            DanRacingD Offline
            DanRacing
            wrote on last edited by
            #5

            @Glynn123 You said in my other post about me porting your cylinder, I advise you to send me the head aswell to get it machined to spec and derestrict it, as for rings, can't beat yamaha original ones for stock yamaha piston.

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