awsome 2 stroke example

Discussion in '2-Stroke Engines' started by brydonb, Jun 13, 2008.

  1. brydonb

    brydonb Member

  2. bluegoatwoods

    bluegoatwoods Well-Known Member

    That is cool.... I never realized that the fuel mixture enters through the crank-case and is forced to the top by the down-stroke.

    two-strokes are interesting engines, aren't they?
  3. duivendyk

    duivendyk Guest

    Present day 2 strokes rarely use these. deflector pistons any more,that's ancient history.
  4. jared3377

    jared3377 Member

    So do HTs use deflector pistons...?
  5. No on the HT engines the intake is alot higher than the firdt representation and the top and the bottom of the piston pass over the intake port, more like #2 if you look closely, you can see where it barely passes over the intake port. That is why porting, opening, reshaping the intake port in the cylinder wall can make such a difference in performance.
  6. duivendyk

    duivendyk Guest

    I have no info as to what type of piston HT engines use.Your inference from my post stating that "deflector pistons are ancient history" somehow warrants the conclusion that they use these type of pistons is false.My educated guess is that, since they copy Japanese designs,they use a version of "loop scavenging" pioneered by Dr Schnuerle who worked for the German firm DKW in the ninety thirties.The Japanese later refined his designs (Yamaha,Suzuki and Honda) After the WW 2 all German patents were made available to the allies.HD actually made a version of the famous DKW 125 cc.(4HP).I think they called it the Sprint.I owned a DKW long ago,my first bike,good for 55 mph with the wind in your back,125 mpg,good inexpensive and above all reliable transportation.It is possible to achieve very high specific outputs with tuned 2 strokes,(by porting etc),but the power band is narrow,so you need a multi speed gearbox.
  7. Dean

    Dean Member

    I like this illustration better than the first one.
    As Phil stated, it explains a little more, by showing us the benefits (almost neccessity) for the expansion chamber in the exhaust system.
    But more over, I like how an actual intake passage is shown.
    In the other example, you'll notice that the piston seems to leave the cylinder wall (which is stepped on one side) during the lower half of its stroke, so that the incoming charge has some way to enter the combustoin chamber.
    However, an engine constructed like this wouldn't last past its first upstroke from BDC, since re-entering the cylinder would break all the piston rings.
    Those who know a little about engines would realize what they're actually looking at (its a slot, kiddies), but the unitiated wouldn't think to question that observation, thus they learn incorrectly from the get-go.

  8. brydonb

    brydonb Member

    thanks dean, I am new to the 2 strokes, now that I read your post and think about it, it does make sense. :D
  9. DetonatorTuning

    DetonatorTuning Active Member

    just for those who may be watching my GEBE / GP460 build thread, this animation should help in understanding the effect the expansion chamber has on power production, and why the pipe may be pushing the power right over the top of the belts abilities.

    these things are so efficient that i had to lean down both the low and high circuits on my carb to get it to run properly. the stock muffler has to have richer mix because it is letting so much of it right on out of the engine.

  10. huckersteve

    huckersteve Member

    Nice post. Both illustrations were helpful but indeed the second one, showing the effect of the expansion chamber, was particularly informative.

    Always finding more good knowledge on this forum. Thanks.
  11. appye

    appye Guest

    Huh ... maybe I should rethink my opinion on getting the expansion muffler. This seems like it could dramatically increase gas mileage as well.
  12. DetonatorTuning

    DetonatorTuning Active Member

    hold off appye,

    give me until into next week after my belts get here tomorrow and i can get mine back on the road.

    i'm going to run the stock muffler just long enough to see if it does or doesn't still break the belt loose above 1/2 throttle.

    i'm having to realign my mount strap, which i think was flexing and throwing the drive out of line. this could have been contributing to my belt slipping under power.

    if i can get all my side issues sorted and out of the way i'll know for sure if the pipe is too much or not.

    as far as who all is running the gp460 i think you will be the 5th and atleast 2 of the others started with or went to chain.