Discussion in '2-Stroke Engines' started by 45u, Feb 22, 2016.

  1. 45u

    45u Active Member

    Why do they call them 66/80cc? Does this mean you might get a 66 or 80cc? Some have been telling me there is more then one brand on the 2 cycle engines even thaw they all look alike. What are the better brands and how do you tell them apart or is it just hit and miss?

  2. crassius

    crassius Well-Known Member

    popular explanation is that cylinder is 80cc, but the western world only measures the volume that is swept by the piston which is about 66cc

    due to diff in stroke, rod length & piston height, motors vary from about 66cc to 69cc

    most motors can't be told apart without taking them apart & measuring

    hit & miss describes it well for noobs - takes ordering many kits to find a supplier one likes
  3. 45u

    45u Active Member

    Rod length does not have anything to do with displacement. Only way to increase engine displacement is by stroke or bore. longer rods help to lower the piston speed and rod angle. Have built MANY a Harley performance storker motor as this is how I have made my living for the past 45 plus years. So the quality is about the same on all the Chines engines?
  4. crassius

    crassius Well-Known Member

    that is true about effect of rod length, but that length can be a good indicator of a possible diff in stroke - this can be important with these mostly unmarked parts
  5. 45u

    45u Active Member

    I have only seen to different strokes for the 2 cycle is there more? Do they make stroker cranks? I plain on taking the motor I ordered apart before I ever start it.
    Thanks Jeff
  6. HeadSmess

    HeadSmess Well-Known Member

    yes, quality can vary tremendously.

    the more expensive motors tend to be slightly better.

    i recall my skyhawk black motor had a rounded cylinder rather than the standard square fins/head...rather unique, i thought.
    it took a lot of abuse, lasted me for a long time then passed on to a friend for a few months. sorta feel like getting it running again :)

    another engine, the cheapest available, turned out to be a 66, and everything about it was bad, never managing to get me simply 5km down the road without a failure.

    usually, the self run businesses tend to sell better products than the "ebay" sellers. you need a good reputation to keep in business.

    my three or four "ebay" specials always had issues, whereas buying from a dealer type person...usually much better.

    once you use different vendors, the parts matching becomes a complete nightmare. different skirt heights, different deck heights, cylinder heights, rod lengths, eek...and not one part is labelled or numbered :)
  7. 45u

    45u Active Member

    Doing the math bore 47mm and stork of 40MM comes out to be around 70cc.
  8. butre

    butre Well-Known Member

    the 40mm stroke is the stroker you were asking about. they were originally 38mm stroke.

    this is where I've been getting my engines lately.
  9. 45u

    45u Active Member

    Yep those are the only two strokes I have found. Wonder why someone does not make a stroker crank? They make them for 1/5 scale motors. Have built many a storker crank for Harley s.
  10. butre

    butre Well-Known Member

    people have done one-offs, it's just hard to sell a product when it costs 5 times the price of the engine
  11. 45u

    45u Active Member

    What is one off? all the stroker cranks I have gotten for my 1/5 scale RC come in plus 1 or 2 mm and are almost the cost of a stock stroke. Does not cost any more to make a stroker crank as it does a stock one. Stock cranks for these engines are about $30. Here are some motors I built for my 1/3 scale buggy. The biggest is only 30cc but they turn well over 10k rpm and push 4 to 5hp. Speed cost how fast do you want to go? LOL

  12. HeadSmess

    HeadSmess Well-Known Member

    while people may like speed... it comes at a price... getting motorized bikes BANNED because there is always some idiot that cant behave themselves, followed by some legal bureaucratic type saying how bad they are, followed by draconian legislation and there you go, welcome to NSW, australia thats done exactly that, and banned them.

    sure, it doesnt cost anymore to make a stroker crank. the machinist will happily offset by two mm for free. considering how lax they are in the factories already, more than likely they do this anyway!

    he will happily chuck them in the same bin as all the other unlabelled cranks go.

    the storeperson will happily disregard any information received and proceed to shove each crank in the same crate regardless of any differences in dimensions.

    the distributors will happily set up a lone shelf to take the one or two "stroker cranks" they sell, to supplement their meagre inventory of spares for nothing at all.

    of course, we will ignore the need for any special jig required to press the crank halves together...these are pressed cranks, assembled...with rods. they are not a machined casting like zenoah uses. we will ignore the fact that they are manufactured in china, at a cost, and the less parts to get mixed up the better. not one part is labelled, other than maybe the Z50 on the odd con-rod...

    yep, it IS easy to make a stroker crank... but how many things need changing afterwards? port timings. cylinder heights. piston sizes, both deck and skirts. longer rods. all seems very simple so why not have a go yourself? then if you come up with a procedure, maybe you can sell the idea to the chinese that will do the number crunching...hmmm...100 units sold per annum...extra work, extra complications, no extra profits... no thankyou i hear them saying already...

    only 4-5 hp from a 30cc? can get double that without resorting to modifying cranks.

    of course, having 7hp at 11k is pretty pointless if it cant produce enough torque to get past 7k without a load...

    these things have the requirement of starting off from a standstill, usually with one gear only... and no spinning wheels in the dirt because they only weigh in at 30kg or so. what you gain up top, you lose down the bottom.

    left alone, they seem to do the job required.
  13. 45u

    45u Active Member

    The 4-5 HP is a conservative estimate not a fact. Not all my engines have stroker crank and none of them have longer rods. Even dynos are just a tool and you can put the same engine on two different dynos and come up with two very different results. Yes they are a good tool but not real time. Yes any one can make a dyno say what ever they want. Many that sell motors do just that. Who said I was going to drive my hopped up motor bike on the street or public roads????????? I have built way to many STREET performance Harley motors to know you have to build a motor for the use you want. I do not build street motors that are just top end as what good would it do you on the street??? How much on the street do you think people with a 113 CI or bigger motor runs at WOT? Not much. This is far from my first rodeo!