Plastic Camshaft?

Discussion in '4-Stroke Engines' started by springfieldscooter, Aug 27, 2016.

  1. I see some of the 4 stroke engines utilize a polymer or plastic camshaft.
    How are these holding up?
    Seems like a bad idea to me.
    Any thoughts?
     

  2. Old Bob

    Old Bob Member

    Why would it be a bad idea if it works for hours on end with no wear?
     
  3. How many hours is the question!
     
  4. Old Bob

    Old Bob Member

    I wouldn't worry about it, I don't keep track of hours, but these things on trimmers last virtually forever.I've never seen one wear out. The GX31 I bought 14 years ago is still running.
     
  5. jaguar

    jaguar Well-Known Member

    I think Honda designed it for less pressure on the camshaft lobe which is easier to do on a small engine.
     
  6. This just seems like a horrible idea.
    I spent a good portion of the day researching, and just as I thought, they fail all too soon.
    Horrible idea for longevity .
    The only good thing is they are cheap and quiet.
    Briggs, Kawasaki, Honda, and probably a lot more mfgs. are going this route.
    Sad.
     

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  7. Old Bob

    Old Bob Member

    That's not a Honda cam.Not GX25,25,31,35 nor GXH50
     
  8. gary55

    gary55 Active Member

    If I was going to worry about something on that cam shaft it would be the gear.
     
  9. This is a cam removed from a newer Briggs.
    It seems that other manufactures are following suit.
    Quiets the valvetrain operation, but shortens the life as well.
    Moral of the story.....BAD IDEA!
     

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  10. Old Bob

    Old Bob Member

    I knew it wasn't a Honda part.
    That cam is from an engine size that's not legal to run on a MB.
    So why bother with it here, this a MB forum.
    Moral of the story is that you are second guessing companies with an engineering dept that better funded than you are.
     
  11. Old Bob,
    Please get a good nights sleep.
    Maybe you will feel better in the morning?
     
  12. Steve Best

    Steve Best Active Member

    I was not a believer in the M16 rifle, plastic valve covers and plastic cams, but since I tried the first 2, I have become a believer.

    It isn't the material, but the task at hand that matters. Does it do the job?

    Steve
     
  13. I hear you Steve!
    But putting a utility engine on a motorized bicycle, usually involves governor removal and more rpms as a result.
    From the research Ive done in the past few days, it seems like a horrible idea.
    A lot of guys on the other forums have experienced failure, especially with the Honda and Kawasaki engines.
    So Im going to continue looking for an old America engine, as a result.
     
  14. Steve Best

    Steve Best Active Member

    Springfield, as an apprentice machinist 40 years ago, I ground a double lobe cam (exhausts on 2 cylinders, intakes were bronzed over) on an Austin 4 cylinder engine for the owner to use as a portable air compressor source. With light springs needed for moderate rpm and a good ramp design there is not a huge amount of load. Were the failures from sliding wear (worn out) or from load (breakage)?

    My experience with Briggs is that without a cam change you cannot get much more revs out of them anyway. I always wanted more guts out of my mowers and rototillers and snowblowers. Better to go for more torque anyway. If I wasn't going to rev it to the moon i'd leave the plastic cam and stock springs in there and concentrate on valve angles, porting, angle planed head, better carb and exhaust and maybe some timing advance.
     
    Last edited: Aug 31, 2016
  15. Good advice, and thank you!
     
  16. gary55

    gary55 Active Member

    So this is what I got from this. If you do mods. for more torque at close to stock rpms float isn't a issue. so the stock springs will work fine and the cam will still be at stock load. With the torque increase you could mess with gear ratios and maybe get close to what you were looking for through higher rpm.
     
  17. Old Bob

    Old Bob Member


    That's BS, the only people that have trouble with Honda are those who never change the oil.Removing the governor the engine is now operating outside of its design parameters, you can't realistically hold the manufacturer responsible.
    If you want a performance engine look at the Honda GX 160 and GX 200 cart engine , its well supported with all kinds of speed parts including metal cams , light rods,flywheels exhaust systems etc etc etc
     
  18. This Honda did not hold up very well:
     

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  19. Old Bob

    Old Bob Member

    That engine isn't designed to rev 20,000 rpm.:rolleyes:
     
  20. 20,000 rpm?
    Hondas wont turn 2000 rpm for too long!
     
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