4-strokes vibrate more than 2-strokes??

Discussion in 'General Questions' started by sparky, Jun 11, 2011.

  1. sparky

    sparky Active Member

    I had no idea...

    When comparing a 33cc Chinese 2-stroke to 33.5cc Subaru 4-stroke.

    Altho, my mounting isn't quite as solid, so that could explain it... but some "rc" forums said the same thing. 4-strokes vibrate more. Or at least "felt" vibration, because there's more strokes.

    Just something to consider...

    I like the way the 4-stroke hums, tho. I guess I like them both, but it's a good change now.
    Last edited: Jun 11, 2011

  2. Happy Valley

    Happy Valley Active Member

    IMO, comparing vibration of an EHO35 in not even in the same ballpark. The HT I had vibrated more at idle and by an increase factor of 4 or 5 at cruising speed. The R/S is smoother than even the Mits TLE engines I have.
  3. Neon

    Neon Member

    I don't really believe that. I admit i've never dealt with the subaru, but have used many 2 and 4 stroke engines. 2 strokes vibrate way more than a 4 stroke. IMO something that makes 20% more power per same displacement is going to vibrate more. Try setting a glass of water on each type of engine when idling. may give you a better idea.
    Last edited: Jun 11, 2011
  4. darwin

    darwin Well-Known Member

    Lil soobie is one amazing lil motor. At 1st I was a lil disappointed at the lack of power but after riding it awhile i've adapted and its the perfect MAB motor. Great on gas and just purrs. The quality is amazing 1st pull it starts every time. Most folks say when brokin in it will gain in power too. Perfect MAB motor and it weighs 7lbs too.
  5. sparky

    sparky Active Member

    I think I'd be happier with the speed of a Tanaka or Mitsu... but I'm down to try this out.

    Hit WOT a couple times today on the end of its first tank (1/3rd gal). One more tank then I'll change the oil.
  6. sparky

    sparky Active Member

    MMmmm.... I dunno. I finally let her ride all the way WOT for a longer length of time. Starting to come in nicely!!!

    And yes, the 2-stroke definitely does vibrate more. I can feel much less vibration in the pedals and handlebars now. The feeling is just the extra strokes jerking in different directions (my drive sprocket isn't exactly parallel with its matching sprocket, also). I guess it's just a different feeling, but I'm getting used to it.

    I can even feel the pull against these extra hard winds that have come out of nowhere... WITHOUT bending down. Comin' in nicely!
  7. 2 strokes don't need as heavy a flywheel as a 4 stroke, which has to provide enough mass to provide adequate rotational momemtum to keep the crankshaft turning through 3 nonpower strokes. Since engine balance is primarily a function of the flywheel on these small engines, 4 strokes with their heavier flywheels tend to be better balanced and so to vibrate less. A 2 stroke could mount a heavier flywheel, but extra weight and slower throttle response would result, and who wants that?

    The old original Solex, Lawnboy lawnmowers, and especially the old Maytag washing machine engines are examples of 2 strokes with heavier than nessesary flywheels. They are all smoother than the HT and most 4 stroke singles, but are heavier and don't have the instant throttle response we have come to expect from lightweight 2 strokes.

    Any engine design is a compromise of many factors. We have come to expect 2 strokes to be noisier, and to vibrate more than 4 strokes. We also expect them to have lighter weight, more power, and instant throttle response. The weight factor has many advantages, of course. The drawback to making the lightest possible engine is more vibration and shorter life. The Chinese HT is an example of a cheap, light, fairly powerful, low quality engine, that will vibrate quite a lot. It's cheap price had led it to become something of a throwaway.
    Last edited: Jun 12, 2011
  8. darwin

    darwin Well-Known Member

    Any one whos ever used a weed whacker for an hour will never hold a steady cup of coffee for awhile.
  9. Neon

    Neon Member

    Or used a chainsaw with no anti-vibration mounts for a full 8 hours.
    If you really want a 4 stroke to vibrate more you can always snap off a fin or two on the flywheel.
  10. jamesburr36

    jamesburr36 Member

    My 1st motorized bike was with a HT 2 stroke. **** thing vibrated so much my hands often went totally numb. I had to try to shake it out. I'm woing on a 4 stroke kit and I have trouble finding the words to describe how much better it is. Sure it lacks the raw torque that my 2 stroke had but I couldn't care less. Also the 4 stroke is so much quieter than the 2 stroke was.
  11. darwin

    darwin Well-Known Member

    Ive Killied; Dont Do It!