Home Forums 2-Cycle Racing HPV/KPV rebuild info

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    • #40669
      Chris Towers
      Participant

      Does anyone know where I can find information on building these motors? The manual I’ve found online (It’s the one for the HPV 100) doesn’t provide much info at all. I’ve seen that there is a book on building KT-100s and imagine some of the procedure carries over, but still leaves me sorely lacking on info directly pertaining to the HPV/KPV series of engines.

    • #40697
      Walt Gifford
      Participant

      I’ll tell you this, you can’t do it with just hand tools and the tools you need are a big investment. Do you want to get into the engine building business? The KT100 book is a good place to start for some general knowledge but, there are allot of details you learn from being brought up in the mechanic/machinist trades that are hard to learn from books or the internet.

      Gif

      FAA certified jet engine and aircraft technician,
      Nicholson Speedway class champion 2001,
      Yamaha KT100 Service Center,
      41 years karting experience

    • #40863
      Glenn L Riggs
      Participant

      Hey Walt have a question and thought you would be the guy to ask. How much wear on the crank main  bearing is allowed before performance start to degrade? Replace at .001 ? Whats your findings? I am sure you would know. Thanks

    • #41005
      John Mulvihill
      Participant

      Hi Glenn,

       

      Not Walt, but here is my opine.

      I usually tear things apart at 6 hours (road racing).   If I find that the ball bearings are no longer mirror shiny, I replace (usually).   I also go 12 hours on the crank pin roller bearing unless it looks funky or the rod looks like it has run hot.

       

      John

    • #41238
      Walt Gifford
      Participant

      Are you talking about wear between the crank and the ID of the main bearing? I use to worry about that until I saw how they clearance the shaft on 125 shifter engines to loosen it up.

      FAA certified jet engine and aircraft technician,
      Nicholson Speedway class champion 2001,
      Yamaha KT100 Service Center,
      41 years karting experience

    • #41311
      Glenn L Riggs
      Participant

      As a matter a fact I am talking about a tm special balanced crank 125 icc engine. when you make the wheels and shafts straight dead on the bearing on the pto is worn to a little over .001 on the journal. Engine has seemed to be a little unhappy pulling much over 13800 my other tms pull 14400 and was just wondering if the crank could be the reason. I remember somewhat the same happening back in the day with kt100. When we ran pipe and twisted the heck out of them, cranks didnt last long.  Thanks for looking Glenn

    • #41349
      Walt Gifford
      Participant

      A customer had 2 Comer ICA reed engines, one built in Texas turned 500 rpm higher than the one I built but mine got lower lap times. At some point it’s hard to quantify these things.

      Gif

      FAA certified jet engine and aircraft technician,
      Nicholson Speedway class champion 2001,
      Yamaha KT100 Service Center,
      41 years karting experience

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