HS 142 "Giant Boulder 4" build.

Discussion in '4-Stroke Engines' started by Pete Lawrence, Jan 8, 2013.

  1. Pete Lawrence

    Pete Lawrence New Member

    This is my just recently finished 4 stroke build, my first, may i add. (Id had previous experience building 2 strokes, but this was an entirely different beast) And i have a couple of questions for you more advanced motorbicyclists. Whilst the HS 142 seems to pack plenty of low end power, it seems to die out a bit towards the higher end, it sure screams, but i dont feel the power. Are there any reasons for this, or is it just how the HS/4 strokes in general work? Also, how often do the connecting rods on these things actually break? It feels pretty solid to me, but then again, i dont even know if there is a way to tell what RPM the engine is running at other than listening to it. Long story short, have you got any tips?

    Also, Pics of my new build:

  2. Ludwig II

    Ludwig II Member

    There are battery operated rev counters you can get from kart or motorcycle race suppliers.

    I've seen pictures of snapped rods as well with these engines, so max rpm may well be above max safe rpm. Any higher speed will probably require a gearing change. I would think most of your questions are answered on the 4 stroke engines section anyway.
  3. MotoMagz

    MotoMagz Member

    Theses little engines will run forever.You should check/adjust your valves.
  4. GearNut

    GearNut Active Member

  5. wheelbender6

    wheelbender6 Well-Known Member

    Cool. We don't see many mountain bikes with thumpers mounted in the frame.
  6. Pete Lawrence

    Pete Lawrence New Member

    Really? Is there a reason for this? I would have thought theyd be pretty common, since being shaken up and beat around is what mountain bikes are made for, and thats pretty much what the engine does...
  7. Ludwig II

    Ludwig II Member

    I think there's a style/cultural thing that leads people to use the clasic American frames. Having said that, the ally frames might fail from vibration fatigue after a while.
  8. Stoltzee

    Stoltzee Member

    Thats the same kit I got! Had lots of torque because of the rear sprocket size(50 or 52?) The real problem is that gearbox. The tiny sprocket inside starts to wear down immediately, and you'll start to feel slippage, and then a constant chatter/****. Better start looking for something like a belt drive. The old sprocket came in handy as a shim for my new setup though. I did eventually open up the exhaust a little at a time until the engine seemed to flow open through different operating ranges.
  9. dougsr.874

    dougsr.874 Active Member

    You are already screwed......Replace the "Hoot" gearbox before it leaves you side of the road......
  10. Pete Lawrence

    Pete Lawrence New Member

    It doesnt matter now, turns out the piston ring is wrecked and the engines lost compression. The gearbox had nothing to do with its eventual demise...
  11. dougsr.874

    dougsr.874 Active Member

    I've been using the same engine almost daily for about 5 yrs. and it still performs flawlessly.....you must have had it really wound up....