Everything2Stroke - What is your Sleeve shrink fit?
  • What is your Sleeve shrink fit?

    In this article, John Tice will discuss the various different methods and procedures for sizing a sleeve, as well as interference fitting, and shrink fitting. - Billy


    Quote Originally Posted by Tim Ey View Post
    About the discussion gasket on the cylinder head or between cylinder and motor:
    It depends on the steering timing you get as a result. Some engines have so moderate steering timings that you can not make a mistake with putting a "down" gasket on them (for example a gokart or Moto-X engine, which is basical made for children). But in an Engine which is made for high performance at high revs (for example a Moto GP Cylinder or a newer Honda CR80) you would get so much steering timing, that your engine runs worse than before.
    A very good lecture about this theme is the Book "The Basic of Two Stroke Engines" from Prof Graham Bell.
    The best way to decide which steering timings you choose in your engine is a Time Area diagnosis (To understand it, read Prof Blairs Book, or the Book from Gordon Jennings).
    This works very well with the Programms you get from Billy at www.bimotion.se
    I prefer working with the Time Area method because (with it in mind) you can not make big mistakes in your porting.

    John, your question if an Bridged or a Tripple- Exhaust port makes the best power you can clearly say: both.
    In Moto GP engines like Honda RS125 or Aprillia RSW125 there are both kind of port geometries (Aprillia got 3 Port-Exhausts, Honda and most others are using a single bridged port)

    On a cylinder with has one single exhaust port when it comes from the factory, i would decide to use 3 ports.
    (Here I made some in an 50ccm Kreidler Moped Cylinder:
    http://www.imagebanana.com/view/v7iq...161408_288.jpg )
    Why? When you grinde 2 auxiliary ports to your main port, you can make the bridge between the ports as thick as you like. A single bridged exhaustport requires (in my opininon) a welded "back" because the little bridge which is only in the sleeve can not conducive the heat seriously to the cylinder itself.

    I red your comment to my engine:
    The sleeve will get a wall thickness of at least 3,5mm.
    My main question is how much the liner should be bigger than the bore of the cylinder?
    I thougth of using an intereference fit of 0,03 to 0,05mm (0,0012 to 0,0016 inch). Would that be ok?


    Hello Tim: Are you getting ready for the winter weather in Germany?
    Your question about your liner fit is so critical and many people are unaware of its importance. I can help since I’ve already figured out a few things although you need to check them over for yourself. We’re talking about the coefficient of linear expansion. You need a set of measuring tools including a dial bore gauge. You also need a 500-600 deg. temp stick from your local welding supply. Don’t be offended when you already know some of this, it’s also for the benefit of other readers. I’ve tried looking this up but found that I needed to do it myself as you do.
    I’ve found that the coefficient for aluminum is close to .005” per 100deg. This is easy for you to remember (5*5). When you heat your cylinder to 500 deg. it will expand about .025”, or 5*5=25. The rule of thumb from most everyone is, the shrink fit for a liner your size is about -.003”. There is plenty of “About & Around” in this write up. You need to confirm everything for yourself. With +.025”-.003” you’ve got .022” clearance when heated to 500deg. This is plenty of room for you to drop in the new sleeve. Still, you must move quickly in order to keep the new liner from sticking while lowering into place. (I’ll send you a copy of my Motor Math spread sheet in a separate email)
    You need to measure the bore diameter of your bare cylinder both hot & cold. Write all of this down, I can never remember all of this stuff. LOL

    Heating the cylinder: Any kind of torch is fine, I use a propane torch with a Weed Burner attached. You also need to be careful not to overheat the cylinder. Carefully working the torch around the cylinder gives an even heat. I keep my heat stick handy in my other hand for keeping track of the temperature. Frequently touch or draw a spot on the cylinder, when you’re up to temperature the heat stick will “Smudge”.
    Find a scrap cylinder to test your skills before you have a “fin meltdown”. I learned this trick way back when that you need to use and understand. With your “Scrap cylinder”, start heating up a fin. At around 900 deg. The aluminum will start to melt. Here’s the TRICK. Just before the aluminum fin starts to melt, the heating flame will change colors to a bright Red,Orange. You need to do this; it’ll save you the embarrassment of a melted and collapsed fin or other parts.

    Tapping into alignment then putting a weight on top: I use a selection of brass rods to tap the liner into alignment with the cylinder. You have 10-20 seconds to tap things around. If the sleeve gets stuck in a crooked position, you’ll probably need to cut it out and start all over. BIG PROBLEM, been there done that.
    After the sleeve is in & aligned a weight is put on top to hold things in place. If you don’t weight the new liner it will raise like you squeeze your tooth paste tube. We don’t trim the upper portion of the sleeve until the parts cool off.

    Heating cylinder, waiting for the sleeve to drop out. This one caught me off guard. European cylinders are usually installed with a press fit. This Husky liner was cast in and had to cut out. Be careful when you do this kind of work, it’s complicated enough that I like to stay focused. Anybody who is good at liner installation and high quality port work can probably walk on Water.

    Measuring the bare bore ID while cold. I don’t know why people always carve their names on their work. Kinda catches them with their Pants Down.

    Heating a Briggs bore

    Measuring while hot

    Fuji cylinder with new liner top view. You can see the Smudge Marks from the heat sticks.

    Surfacing the top “Decking”. A .005” lip is left at the top of the new cylinder sleeve. Doesn’t matter who does the work, chances are that the new liner will drop and blow a head gasket. Enough to catch your finger nail.

    Another ID bore check

    Close up. .005” lip on top of new liner. New threads in the head studs. Anybody have any questions, please Chime in. We can all learn from this.
    Next Time
    “Old Dog”
    This article was originally published in forum thread: How It's Done - Projects around the Shop started by John Tice View original post
    Comments 3 Comments
    1. DMoneyAllstar's Avatar
      DMoneyAllstar -
      One of my LT500R cylinders has what was called a "mini sleeve" and described to me as a sleeve within a sleeve. Why would someone do this vs. a full re-sleeve? Is a mini-sleeve practical? Durable?
    1. Sigmaz's Avatar
      Sigmaz -
      Hey JT,
      What the Fuji Cylinder from?
      Looks a lot like my Fuji Cyl on my Subaru 360.
    1. seattle smitty's Avatar
      seattle smitty -
      Tim Ey, you mention that you think a single skinny exhaust bridge has an inadequate area at its ends for dissipating heat. I agree. I think the bridge gets hotter than the rest of the sleeve, expands more, and can bulge in some direction, very possibly bulging into the cylinder. My crude solution for this possible problem is that when I give a cylinder its final hone-to-finished-size, I first warm up the cylinder with a torch, and at the last second I get the bridge quite a lot hotter to make it bulge, then quickly complete the finish-honing. I should say that I have bolted and torqued down a dummy head that has a hole in it for the hone to pass through.
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