Average speed of 2/stroke

Discussion in '2-Stroke Engines' started by geebt48cc, Mar 18, 2010.

  1. geebt48cc

    geebt48cc Member

    Running around 20-25 is just fine around the city thing. The "Boys in Blue" just don't understand a bicycle going much faster than that. So, 80cc and 48cc have about same top end? :rolleyes7:

  2. AussieSteve

    AussieSteve Active Member

    Yep, I agree, more than about 25mph not only upsets the cops, but cars aren't sure how to react. Too often, when they see a bicycle, they judge it's speed as lower.
    I've had countless cars cut in front of me at roundabouts and intersections, because they thought they had enough time.
    On the open roads, though, I sit on 35-40mph.

    From what I've read here, the 48cc engines rev higher, but the 66cc has more overall power. ie The 66cc would rev higher up hills.
    Apparently, the engines' bottom-ends are balanced for the 48cc top-end, hence the higher revs in the 48.
  3. geebt48cc

    geebt48cc Member

    Yes Steve, I very much agree, but the only reason I went with the 48cc is because of the legalities. I really need that extra cc's of the 66, but I figure that I can feel better about telling people that I road 20 miles and peddled up some good sized hills.

    Uno, pretty good averaging 22 mph isn't bad in the hills of SW Va. Uno, I've been told that I need to get a expansion pipe. Wonder how much that would help the 48cc Grubee

  4. AussieSteve

    AussieSteve Active Member

    22mph is fine.
    Our engines have nothing on them to indicate their capacity, and since the 48cc and 66cc look the same...
    Still, we're restricted to a max of 200W, therefore both 48s and 66s are technically illegal.
    They turn a blind eye, for now. I've been seen by more cops than I can remember in 500km and they've never stopped me. Too fast, I always get away. (kidding)
    Even went through a 'random breath testing' station and the cop winked and signalled me on.
    If I am stopped, I'll say it's a 200W 48cc engine and cross my fingers.....
  5. Lazieboy

    Lazieboy Member

    48cc vs 66cc

    Steve, I got a 66cc grubee and i took all the badges off it and altered proof of purchase to show 49cc so when i get my title from state (or if) its a moped not a motorcycle. legal loop hole in MN. hopefully they dont want to do an inspection. think they would find out if inspected
  6. AussieSteve

    AussieSteve Active Member

    Yeah, I was thinking of buying a Rock Solid Engines certified 200W, 48cc engine, then fitting the 66cc top-end from my current engine.
    We need that cerificate here - the onus is on the rider to prove his engine doesn't exceed 200W. It's not up to the state to prove otherwise.

    Since, for you, it's a capacity issue, you'll probably be OK, unless they pull the head off and measure the bore and stroke during inspection, but that's not likely.
  7. motorpsycho

    motorpsycho Active Member

    well, yes...a 66 c.c. (80 c.c.) has more bottom end torque than the 48 c.c., but top end speeds are pretty much the same. I have a 48 c.c., my friend has a 66 c.c. we both have pretty much the same set-up as far as bikes, wheels and rear sprockets go. (he has a few pounds on me as far as our weight goes).
    bone stock, his bike would walk away from mine on take off, but i could catch him and SLOWLY pass him on the top end.
    since then, i've added an expansion chamber a high flow air filter and tuned the carb. his is still all stock and he can still get me on the take off. but now i can catch him sooner, and on the mid range / top end, i can pass him and keep going with no problem at all. he can't catch up to me once i pass him. i have a speedo on my bike (not sure how accurate it is) but it's been reading 28-30 mph on the top end.
    listening to the 2 engines, it's obvious that my 48 c.c. revs higher and quicker than his 66 c.c.
    the advantage to the 80 c.c. is the bottom end torque.
    Last edited: Mar 19, 2010
  8. Lazieboy

    Lazieboy Member

    Whats onus. and whats 200w = to in usa
  9. AussieSteve

    AussieSteve Active Member

    onus means 'burden of proof'

    200W AU = 200W US = 0.268096514745308310991957104557641 horsepower, (approximately)

    Not much, is it? About 1/10 the power of a standard HT engine.
    Last edited: Mar 19, 2010
  10. Hajuu

    Hajuu Member

    wow really? I think it's law that they have to be marked, yeah? the 3 i've seen from 3 different vendors were all marked with cc, serial number, etc.
  11. AussieSteve

    AussieSteve Active Member

    You think wrong. There is no such law in Australia, yeah.

    Three engines from three vendors? Which three vendors?

    I think that Grubee engines have a plate, because they're intended for the US market, but I haven't seen them on others unless, again, they're intended for the US market.
    There is no capacity restriction on our engines, only the 200W power limit.

    My engine has a four-character serial number, but that's all.
  12. 210061741

    210061741 Guest

    Here is the deal.

    The 48 cc revs up faster cause the piston is smaller and weighs less. ( Fact )
    Lighter piston = faster revs.

    I think out of the box most of the engines will go 20 to 30 mph.
    Not dependant on engine size.

    Alot depends on the users ability to proper tune the carb.

    The carb being a hair rich or a hair lean makes a big difference on the overall engine performance.

    Too rich and it will 4 stroke and loose power and speed.
    Too lean and you don't get enough fuel in the engine means it runs way hotter and the max speed is limited by the amount of fuel you can get in the engine.

    I would spend a huge amount of time to get the carb right cause on a stock engine it will make the biggest difference.

    The second largest contributing factor is the engines ability to breathe.
    To pass the required volume of gasses through the area of the cylinder port in the time provided by the duration that the port stays open efficcently at the desired RPM.

    Even with the best of porting configurations a cat exhaust or any exhaust with a small header that is restrictive will reduce the engines ability to breate.

    That is where the Expansion Chamber comes into play and is the best upgrade to buy 1st.

    #1 it allows the engine to breathe and #2 the sound waves cause suction and closing of the exhaust port which increases the pressure in the cylinder and produces more power.

    SO IN A NUTSHELL THEN....the engines ability to breathe and the proper carburation are the 2 factors that determine the overall speed of the engine.

    No matter what brand....There all the same except for the PK 80.

    The PK80 has a longer stroke but a shorter connecting rod.
    Also the shape of the combustion chamber and the piston produce higher than average compression which outputs more power.

    I wont go into the con rod to stroke ratio stuff cause it is far too complex.

    Bottom line..........Get the carb Perfect and put any and i mean any Expansion chamber on there


    I can make any engine as fast as the next.

    I hope this was helpful.
  13. motorpsycho

    motorpsycho Active Member

    my engine came with a little yellow sticker stating the mfg. date, serial #, c.c.'s and some other misc. information.
    That sticker was the first thing i took off.
  14. Crobo

    Crobo New Member

    me too.

    " i got the engine off of a weedeater officer, i think its around 30cc" :whistling:
  15. Hajuu

    Hajuu Member

    That's good to know aussiesteve, cheers.
  16. AussieSteve

    AussieSteve Active Member

    What surprises me, Mike, is that in their haste to ban mopeds from the MB category a couple of years ago, they forgot to set a maximum speed and engine size for motorised bikes.

    The poor moped riders are limited to 50kph and 50cc maximum and have to pay rego and hold a license for the privilege.
    We're limited only to the posted speed limits and have no maximum capacity limitation. (Although the 200W limit caps that pretty nicely.)
  17. motorpsycho

    motorpsycho Active Member

    man i'm glad i live in the U.S.A. and in a town where i don't have to worry about all of this mumbo-jumbo!