2 stroke vs 4 stroke

Discussion in 'General Questions' started by Jason A, Mar 21, 2016.


Which engine is better for me?

  1. 2 stroke

  2. 4 stroke

  1. Jason A

    Jason A New Member

    Hey guys, first post for me :)!
    I'm looking at building a my first motorized, and I have two totally different kits in mind.
    Either a 66cc 2.75 HP two-stroke, which costs $119 USD, or a 49cc 2.5 HP four-stroke, which runs $199 USD.
    Both are (obviously,) not super great engines, but I'm on a budget, just looking to have fun. Don't need practicality, as this is purely for fun, and I can ride on basically any terrain, (paved, gravel, grass, dirt, etc.)
    Which of these is better, and is it a good choice? Also, is a 44 tooth sprocket ideal for these varied conditions?
    Thanks for fielding my newbie questions!

    P. S. Other motor recommendations are welcome, too.‎

  2. butre

    butre Well-Known Member

    2 stroke if it's not for daily use.
  3. Purple Haze

    Purple Haze Active Member

    The 4 strokes are better for reliable, day to day tranportation, are more quiet, and less messy and smelly. That said, 2 strokes make more power, are cheaper to buy and work on, and their simplicity allows for easy mods. Aftermarket parts are plentiful and reasonably priced. Plus, they just look cool! I don't care for the lawnmower engine look of a 4 stroke. The fun factor alone makes this choice easy. The gearing is a personal choice, with terrain and top speed factors. I ride in hilly terrain, and use a 48 tooth sprocket to good effect, it'll pull your head off, but on the street it only runs about 25 mph.
  4. bakaneko

    bakaneko Active Member

    For fun go with a 2-stroke for all the reasons purple and butre has mentioned. Also, the HP comparisons (2.75 v 2.5HP) you have listed isn't entirely accurate. The stock 2-stroke and modded one has way more power than the 4-stroke stock. Also, you need to consider the bike you are using too. A 4-stroke is a wider and taller engine. Price conscientious and fun purpose wise I would go with the 2-stroke.
  5. libranskeptic

    libranskeptic Member

    dont trust my numbers, but some ~philosophy that may help here:

    you dont mention weight, a key factor, but the effect of savings depends on total bike load - u plus the bike.

    this favours 2 strokes - no valves and fancy head.

    2 strokes are maybe 30% more powerful in theory - double the power strokes

    either engines power is huge. 1 hp is ~730 watts? i think, and thats a very decent ebike. an ebike motor based on a common 25cc brush cutter motor is about that i think - small, light, cheap, mass produced quality & reliability

    single cylinder motors are inherently unbalanced & sound & feel crappy. done well, a 4 stroke will sound and feel much calmer to hear and ride.

    for suspension, just use big, not too hard, tires

    chainguard is important

    a hydraulic clutch sounds good if they exist - comments?

    this seems very cool

    Motorized Bicycle with Jackshaft Kit - ie - 7/8 gears
  6. Jason A

    Jason A New Member

    Dumb question, I know, but will a normal chain guard work? I see no reason why not, but I'd hate to order one and find out it doesn't fit...
  7. bakaneko

    bakaneko Active Member

    I haven't seen one kit that did not come with a chain guard. Also, the chain guard is optional. I rode 1500+ miles with no chain guard. For 2-strokes, I can imagine the chain guard adding a nasty rattle. I don't wear shoes with laces so no danger there and spray chain protector on my chain periodically.
  8. Charles Laypool

    Charles Laypool Active Member

    I would stay away from the 199.99 4 stroke chain drive the gear reduction is not enough i built a fat tire 4 stroke for a customer and he burned the clutch up in 3 hours of use with a 26inch tire and 44tooth sprocket its geared to go 45mph and the engine cant do that so ur clutch slipps and slipps till u overheat ur bushing and seize the gear box get the 7g(ghost racer)if u favor 4 stroke is goes 26mph with 26inch tire and 44tooth sprocket iv used it for 2 yrs and replaced only a belt
    libranskeptic likes this.
  9. libranskeptic

    libranskeptic Member

    re chainguard, a chain on both sides sound fraught to me, the second one being far more treacherous.

    it seems right it should come with a kit

    given the drive is usually on the opposite side, a normal guard seems unlikely to fit.

    if u r not swapping sprockets for gearing, why not. A major bonus with IGHs (which suit a guard), it was pointed out to me, is dead simple chain lubing thru a hole in the guard after a big ride in the dirt.
  10. 45u

    45u Active Member

    When you run wider tires you are putting more wasted HP to the ground which will put a lot more strain on the motor and clutch this is why I like to say with a tire a little over 2 inches. The reason my first kit was a 2 cycle is because they make many hop ups for the 2 cycle and all most not for the 4 cycle. I will build a 4 cycle one day.
  11. libranskeptic

    libranskeptic Member

    my old bones fel the bumps after so screw a little power here and there. I mean, vs suspension, which is heavy (you lose over a kilo, net) & also chews power, and has delayed effect, unlike give at the point of contact with a bump.
  12. 45u

    45u Active Member

    That is why I have suspension in the front and a good big spring seat and thinner tires. Not only does the contact patch of the tire eat up HP but rotating weight is all so a BIG HP eater much more then you many think. At 61 and over 200 pounds I need all the little bits of HP I can get.
  13. KCvale

    KCvale Motorized Bicycle Vendor

    2-stroke hands down.
    Lighter and smaller and it won't matter to your job when it breaks.
    It will be a hobby toy that will need a lot of fixing.

    When you want reliable and easy to operate and maintain that's where 4-stroke rule in so many ways.
    They run on regular gas, have a pull start, far less vibration, and an automatic clutch.
    libranskeptic likes this.
  14. libranskeptic

    libranskeptic Member

    Yes, bikes are incredibly subjective. all opinions are subject, among many things, very much to the total mass carried. a kilo more matters little to you at 200+ pounds vs my 150 lbs~.

    my alloy MTB with suspension max load is 120 kg, so even I would just scrape in on a motorized such bike.

    I still like a bike i can lift/heft tho.

    It probably helps to be more asian size :). they are the main target market for bikes, not we westerners.

    I have been astonished how light my MTB wheels are rather than their weight. am skeptical bigger tires add much.

    a wacky thought I had, as mostly i take bumps sort of standing, was wear pump up sneakers, or a pedal shaped pneumatic cushion over pedals~.