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Thread: ESE's works engine tuner

  1. #39961
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    12th March 2010 - 16:56
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    Quote Originally Posted by Frits Overmars View Post
    We use alloys with a silicon content of over 30% for pistons: https://www.rsp-technology.com/
    The silicon keeps the expansion coefficient under control. The downside is that alloys containing so much silicon will eat milling cutters for breakfast.
    https://www.youtube.com/watch?v=ZwbEuzJCnqI
    And heat transfer is poor.

  2. #39962
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    12th March 2010 - 16:56
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    Wobbly, what down angle on exhausts? I wrote it down somewhere, probably on a peice of wood, then promptly used it for pattern making somewhere.
    27 degees rings a bell.
    The square bore and stroke twin port, water cooled, powervalve cylinder emerges. Straight ports this time not curved like the air cooled cylinder. Hold down studs come up from underneath so free hand in where the exhausts go, no need to compromise for nut fitment or room for a spanner.
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  3. #39963
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    20th January 2010 - 14:41
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    Quote Originally Posted by Frits Overmars View Post
    Just how closely do you want the expansion rates of piston material and cylinder material to match? The ideal would be 1 to 1 if piston temperature and cylinder temperature were equal.
    But they're not. The piston gets a lot hotter than the cylinder, so its expansion rate should be lower, like a steel piston in an aluminium cylinder.
    It does work on foulstrokes. The problem is that the dome surface temperature of the steel piston would be sky-high, and two-strokes do not like that.
    Foulstroke manufacturers get away with it by cooling the piston from below with multiple oil jets. In crankcase-scavenged two-strokes we cannot have that luxury.
    Attachment 355131
    To deal with this we build in taper ,ovality, cam grinds and cut outs even splits and in old ones wire winds and also expansion strips or fillets as in your pic
    As well as the oil jets they use more rings, oil on the cylinders and a cooling stroke with much less output per area.
    then you throw in the slippery coating and the groves for oil.
    I am not sure on a 2t how much heat is transmitted from the rings but on a 4t from what I have read on its far more than most people appreciate.
    In an ideal world the 4t skirt will expand just enough to increase the surface area to again be able to transfer the heat when needed.
    I was trying to find the clearance on a modern 4T big twin that was mentioned the other day but it was tiny, but then again so was its output/liter.
    (edit)Victory air-cooled engine 2nd gen was 25 micron or 1.5 thou. On a 850 cc cylinder 101mm bore.

    The piston in your pic
    A late model MX bike is now very similar. just with more aluminium to bake up for the 1/3rd strength
    My son races YZ450f Supermoto, even with its GYTr twin oil jets the fully synthetic oil changed at about 30 minutes, the piston is good for 8 hours the camchain less then 4.
    no big deal other than how bloody much harder it is to do than a 2t is.
    3x the cc of a RSA and only a few more hp.

    the cutouts below the bottom ring land are to get the pin in and out



    Kinky is using a feather. Perverted is using the whole chicken

  4. #39964
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    8th February 2007 - 20:42
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    Neil , 25* is optimum.
    And the other posts mentioned point is that the majority of heat dissipation from the piston ,out to the bore in a 2T occurs on the bottom ring seal face.
    The very first sign of deto starts at this surface - resulting in the term " power deto " coined by Franco Drudi of TM Championship winning fame ( my boss ).
    As this process creates free radicles that start eating away at the hottest surfaces trying to recombine the single free electrons that are a result of the detonation phenomenon.
    Creating deto uses up a huge amount of the available fuel energy , and this is what we use when data logging the EGT , as it initially flat lines with the first over lean jet change
    then drops with the next.
    Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.

  5. #39965
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    12th March 2010 - 16:56
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    Best I write it on the shed wall, so I can't lose it in the future. ��
    Thankyou.

  6. #39966
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    7th October 2015 - 07:49
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    Steel pistons with iron cylinders were used in Anzani radial engines from 1909.
    Later British Anzani produce very interesting two stroke boat racing engines, with combined piston port and rotary intake through the center of crank webs.
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  7. #39967
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    8th November 2015 - 17:28
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    Quote Originally Posted by katinas View Post
    Steel pistons with iron cylinders were used in Anzani radial engines from 1909.
    Later British Anzani produce very interesting two stroke boat racing engines, with combined piston port and rotary intake through the center of crank webs.
    Where have You found these pictures or engines?
    The boat engine is interesting and looks like a Trabant but with much fewer parts.

  8. #39968
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    7th October 2015 - 07:49
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    Quote Originally Posted by Niels Abildgaard View Post
    Where have You found these pictures or engines?
    The boat engine is interesting and looks like a Trabant but with much fewer parts.
    I took piston pictures in the Italian Air Force Museum at Vigna di Valle, on Lake Bracciano. I went to the museum with my son this year, because he is very interested in military planes and especialy wanted to see the real, fastest red hydroplanes from "Porco Rosso". Apart many interesting things, unfortunately I didn't see a single two-stroke engine.
    Later at home checked Anzani and found this https://www.boatracingfacts.com/foru...Engines/page30
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  9. #39969
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    23rd January 2012 - 05:03
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    Durham Ct. USA
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    katinas's Anzani pictures

    Scrolling though Kiwi Bikers this morning and the pictures of the Anzani crankcases caught my eye. First think that came to mind was that someone in Europe was epoxying them up just like the ones in my shop. Then I read further and found out the pictures were off Boat Racing Facts. The pictures were posted by John Taylor. A few years ago he got sick and all the Anzani parts were sold to Jim Hunter, a friend of mine. They are in my shop for restoration.

    Small world.

  10. #39970
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    20th October 2024 - 02:34
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    Piston for 50mm cylinder

    At the moment I’m searching for a piston fitting to 50mm cylinder.
    14mm wristpin
    Piston ring at 6 o‘clock. Max 1mm thickness.
    Compression height 28-30mm
    Cylinder is Nicasil 50mm stroke

    Any suggestions?

    The piston belonging to the cylinder is from Mahle.
    Big chamfer around wrist pin hole which favours short circuiting between Exhaust and A-transfer

  11. #39971
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    30th May 2020 - 23:45
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    Quote Originally Posted by Mollihead View Post
    At the moment I’m searching for a piston fitting to 50mm cylinder.
    14mm wristpin
    Piston ring at 6 o‘clock. Max 1mm thickness.
    Compression height 28-30mm
    Cylinder is Nicasil 50mm stroke

    Any suggestions?

    The piston belonging to the cylinder is from Mahle.
    Big chamfer around wrist pin hole which favours short circuiting between Exhaust and A-transfer
    Have a piston from italkit here with ringgap at oposit to main ex

    Measured for a quick look comp hight..25

    Its from a big bore kit for minarelli am6

    But maybe you should have a look at wössner

    https://www.woessner-kolben.de/fileadmin/Downloads/Kataloge/Motorrad_Inhalt2018%20print.pdf

  12. #39972
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    18th March 2004 - 17:38
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    Quote Originally Posted by Mollihead View Post
    At the moment I’m searching for a piston fitting to 50mm cylinder.
    14mm wristpin
    Piston ring at 6 o‘clock. Max 1mm thickness.
    Compression height 28-30mm
    Cylinder is Nicasil 50mm stroke

    Any suggestions?

    The piston belonging to the cylinder is from Mahle.
    Big chamfer around wrist pin hole which favours short circuiting between Exhaust and A-transfer
    Yeah, Wossner and other aftermarket piston manufactories do over size big bore pistons for 85cc MX's that might be the go.
    Compare Pornography now to 50 years ago.
    Then extrapolate 50 years into the future.
    . . . That shit's Nasty.

  13. #39973
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    20th October 2024 - 02:34
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    I do have Wössner and Wiseco for Suzuki RM85.
    But they both have a compression height of 27mm which is only usable for me in case I mill down the casing by 1mm.
    Want to avoid that
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  14. #39974
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    20th January 2010 - 14:41
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    Quote Originally Posted by Mollihead View Post
    I do have Wössner and Wiseco for Suzuki RM85.
    But they both have a compression height of 27mm which is only usable for me in case I mill down the casing by 1mm.
    Want to avoid that
    Honda cr85/100 have a crown height of 24mm
    https://www.mitaka.co.uk/piston.php?id=2

    there are old school rm100 as well that were 50mm ish based on the 125cc air cooled rm

    or YZ is given as being
    26.5
    https://www.mitaka.co.uk/piston.php?id=78

    or troll through Rolfee
    https://www.pvlsverige.se/vrm/kolvar/kolvar.html



    Kinky is using a feather. Perverted is using the whole chicken

  15. #39975
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    30th May 2020 - 23:45
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    This is italkit vertex... look at last picture to clarify Dimensions 😉

    Comp hight 25,2

    https://www.langtuning.de/Italkit-Ra...m-Kolbenbolzen

    Comp hight 28 but 12mm pin
    Maybe change needle bearing 😉

    https://www.langtuning.de/LT-Performance-1-Ring-Kolben-90-ccm-50-mm

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