The Basics, Port & Polish and Port Matching

Discussion in 'Heads and Cylinders' started by BarelyAWake, Mar 20, 2010.

  1. BarelyAWake

    BarelyAWake New Member

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    To make a long, overcomplicated and often misunderstood story short;

    The castings on these china kits is quite sloppy, the cylinders in particular. With an extremely rough surface and lots of casting flash, the flow of fuel, air, and exhaust is made turbulent - a little time spent cleaning up the mess can result in a smoother running engine. Often the intake and exhaust manifolds are up to 1/3 smaller than their ports - expanding them increases flow.

    Porting and polishing isn't nearly as difficult as some seem to think. "Porting" is simply attempting to get the intake and exhaust manifolds and ports to share as close to the same size & shape as possible, enlarging the manifolds/ports as necessary - "polishing" is ofc just makin' them smooth & shiny.

    It's the same story for the transfer ports except they're a touch tricky as they're a bit hard to reach with a standard dremel bit. While the intake and exhaust ports can be ported somewhat larger (still leaving enough for a good gasket seal ofc), the transfer ports should not be altered beyond removing casting flash and smoothing out irregularities.

    The only "dangers" are scoring the cylinder wall and/or removing too much material, so with just a little care and patience just about anyone can port & polish.

    You are after all just tryin' to make this;

    [​IMG]

    look like this;

    [​IMG]


    Bringin' it to a high sheen instead of a smooth semigloss is up to you ;)
     
    #1 BarelyAWake, Mar 20, 2010
    Last edited: Jun 25, 2012
  2. bairdco

    bairdco a guy who makes cool bikes

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    re: The Basics, Port & Polish and Port Matching

    that first picture looks like some scary prehistoric fish you dredge up from the deep...
     
  3. BarelyAWake

    BarelyAWake New Member

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    re: The Basics, Port & Polish and Port Matching

    No doubt heh :p

    How 'bout this 'un then? (notice the high quality base gasket lol)

    [​IMG]


    If ppl really wanna get the most outa their performance parts, this kinda stuff really outa be dealt with... it's not so much "zomg secrut blueprinting tricks" as just basic clean up. This inattention to detail is one of the reasons the kits are so cheap - the "finishing work" has been skipped to cut costs.

    It's not a bad idea to see what kinda junk might be rattlin' around down in the case while the cylinder is off... I suspect lil bits o'random crap are the cause of at least a few premature failures.




    Rutro... here I am jus' giving away confidential information and performance secrets... THEY'RE COMIN' FER ME NAOW FOSHO!!1!

    |.o
     
  4. bairdco

    bairdco a guy who makes cool bikes

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    re: The Basics, Port & Polish and Port Matching

    this forum needs a new topic.

    "this is how i go fast."

    or somethin...
     
  5. silverbear

    silverbear The Boy Who Never Grew Up

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    re: The Basics, Port & Polish and Port Matching

    I don't agree. I think something on porting for those who know nothing at all about these motors, but would like to learn is a good thing. If you already know all about it then there's no need to read it, but for the newbie to read some of these discussions of high speed stuff is like, well, "Chinese" or trying to read "Greek". And if a new person is not pretty sure of what to do, why to do it, how to go about it without wrecking a brand new motor then they aren't going to try. Imagine that you are explaining this to somebody who is a first time owner of a 2 stroke engine of any kind, or your 13 year old nephew who is really interested, but has little experience with things mechanical. I think this could be even more simple with more hand holding and more closeup photos. For example, the first time person doesn't know about what needs to be taken apart and how to do it. Are there any things to be extra careful about? Does this mean new gaskets? How tight should it be put back together? It is true that porting is not a new subject, but very often it was addressed on this forum without photos and if there were any they were often blurry. The person already in the know understood the discussion perfectly, but the newbie was left on the outside looking in and not much better off.
    A how to for eighth graders is a good thing. A how to so absolutely clear that it is nearly impossible to screw up leads to success. Step one... here's your motor new out of the box. Step two... these are the tools you need to do this job. The one on the left is called a Dremel and the little attachment you see on it is... etc. No, this isn't going to be very helpful to those who already know how and is boring, but to the newbie it will be much appreciated, much studied and will lead to some happy mb campers who can say "I ported my motor and it runs lots better, heh".
    And maybe instead of just the focus on greater speed the slant should be on cleaning up your motor so that it works more efficiently. I would guess that a ported engine just plain runs better. (By the way, some of those 13 year old eighth graders are retired and in their sixties... the baldies in the back row.)
    Another way to approach this is to imagine that you are teaching seniors how to use a computer for the first time. These are smart people who are accomplished in many ways, but computers are new and daunting things for them. But they want to email their friends and send photos to relatives. Teach 'em how. As a former teacher I know that helping empower others is a great thing.
    SB
     
  6. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    re: The Basics, Port & Polish and Port Matching

    Two pictures to show what you want to accomplish? Short sweet and to the point.
    What could be better?

    Thanks you Mr. Awake.
     
  7. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    re: The Basics, Port & Polish and Port Matching

    BTW- I vote for the "satin like finish" over the "mirror like finish" it's slightly better for the flow.
     
  8. BarelyAWake

    BarelyAWake New Member

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    Thanks Joe, and you're right silverbear... I forget the "mystery" of pullin' an engine apart for the first time... I also fear to sound "condescending" when attempting to explain something I think of as basic knowledge... overlooking the fact that it's not "basic" if it's simply unknown.



    I'll start with the basic tools needed;

    A Dremel is pretty much a must-have, you don't need this spiffy one: Dremel 4000-3/34 Variable Speed Rotary Tool (about $75), even a "generic" brand or the $30 base model will do just fine - yet the 4000 is such a great muti-use tool it's a worthy investment should you wish to get one.

    While you can buy individual Dremel bits, they're over priced when purchased separately. Fortunately there's two lil kits perfect for the job & include almost everything ya need;

    Dremel 686-01 Sanding Grinding Kit (usually $11)

    Dremel 684-01 20-Piece Clean & Polish Kit (usually $11)

    Other than what tools you'd need anyway to pull the motor apart (the four head bolts and the intake/exhaust manifolds, 10mm & 14mm sockets) all you'll really need beyond the above is some really fine sandpaper (400gt or finer), some soft cotton cloth... and new intake/exhaust/head & base gaskets ofc - you may be able to pull a new engine apart without damaging the gaskets, but an older, used engine is bound ta need 'em.

    I should mention that ANY alteration of the engine can result in accidents and failure - DO NOT attempt this if you're not willing to say "doh" and get a new cylinder should you mess up or break something. I won't say "don't try this" if you've never done it before as this is the perfect lil engine to learn with... but I will say that even the "experts" screw up from time to time heh

    Oh right - before ANY of this process is started make sure you're working in a clean, dry environment. If the engine is used, clean it thoroughly before you disassemble it. The whole point is ofc to get rid of what garbage may be in the engine - not add more lol You outa have some various containers to put parts in and I like to work on engine parts with some cardboard as a work surface - this helps prevent dinging up whatever part you're working on.

    Remove exhaust
    Remove intake
    Remove spark plug
    Remove four nuts holding the head on
    Remove head
    Remove cylinder

    When removing the head and/or the cylinder you may find it's stuck. DO NOT "pry" at it with a screwdriver or whatever - this aluminum is soft and if you dig at it at all you'll gall it (making it hard for gaskets to seal) and/or break something. One trick is to find a piece of wood that fits in between the cooling fins to the nice, solid cylinder itself (the more surface area the better) and gently tap on the wood with a rubber mallet or it's equivalent.

    The reason its sticking is the gaskets so you may need to tap a bit on one side, then some more on the other. You're trying to get the gaskets to release and they're not always cooperative (one reason I don't like insta-gasket goop). Believe it or not - this may indeed be the most difficult part of the entire procedure... stupid gaskets lol

    Once the head is off the only thing holding the cylinder on is the base gasket being stuck - there's no "hidden" fasteners nor is the piston messin' with ya. If it just wont come off - hit the base gasket with some carb cleaner and let it soak... sometimes that helps. If you've tried repeatedly to get the cylinder off a used engine with no luck at all... you may wish to consider skipping the port & polish and just do the intake and exhaust manifolds. I'm not sayin' it's impossible, but this mod may not be worth broken cooling fins on a used engine - new (just) engines are cheap enough it may not be worth the effort... that's your call tho.

    Now that you've gotten the base gasket free, the cylinder just slides up and off - but be wary, the piston will wanna slap up against the cylinder studs and if it's hard enough it'll leave a mark. You don't want any scoring or marring on the piston or cylinder walls - that's why we're doing alla this heh, so have a lil chunk of cardboard ready to put between the piston and the studs - you may wish to put a clean plastic bag over the piston and case just to keep crud out while yer working... you will be creating some metal dust when ya get to Dremeling.

    *For a better tutorial about pullin' yer head and cylinder w/pics - check Norm's thread out: Engine top end rebuild & engine stand

    Now that you've got yer engine all apart and the cylinder in hand, I'm gonna leave ya hanging for a few as I've got to go get summore parts for my bike and some foodstuffs fer lil ol' me FTW I'll continue babblin' on when I get the chance, other ppl's tips are ofc welcome :D

    To be continued...
     
    #8 BarelyAWake, Mar 20, 2010
    Last edited: Sep 15, 2014
  9. silverbear

    silverbear The Boy Who Never Grew Up

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    re: The Basics, Port & Polish and Port Matching

    Excellent!
    SB
     
  10. john_the_great

    john_the_great New Member

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    re: The Basics, Port & Polish and Port Matching

    I have ta disagree wit' ya thar. When ya do those things (polish, clean up intake and exhaust manifold and match it to the ports you are whats called Match Porting Real porting is a lot more dangerous but it is opening up your ports to allow more flow, change port timing, etc. It is a much more daunting task and dangerous topic for a n00b with a dremel(cuz if you mess up ur engine might blow up as soon as you run it) I am not suggesting people play with there ports but I'm just sayin' that portin' and match portin' is uh different.

    Interestin' story #2 according to my now aging father back in the day of husqvarnas ruling the race track(watch any sunday great movie) a fad came out to polish up intake manifolds so that they were mirror shiny and extremely smooth. The funny thing was tho was that once it was that smooth the fuel didn't atomize as well and they found have a rougher intake actually was better.(without casting burs of course, those need to be removed!) This is just a story that was told to me, but I thought it was interestin'.
     
  11. BarelyAWake

    BarelyAWake New Member

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    re: The Basics, Port & Polish and Port Matching

    Yarp - good call on that distinction and thanks, I r just tryin' to "keep it simple" if ya know what I mean - the castings on these HT's so sloppy something must be done heh

    I've messed with the intake and exhaust on these things, there's not much meat fer opening them up any more than what you see in the pic (still need a face fer the gasket to seat ofc), there's been nothing but good to come of that small amount larger (about 1/8" overall).

    I've not had a chance to warn anyone to not alter the actual shape as I've not gotten there yet lol - but still, good info man!
     
  12. GearNut

    GearNut New Member

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    re: The Basics, Port & Polish and Port Matching

    Just my .02
    Intake ports are best left as a satin finish to promote atomization of the incoming intake charge. They will still flow plenty fast.
    Exhaust ports are best left as a mirror polished finish to promote fast flow and reduce the chance of carbon build up.

    The above is what I was taught by pros in the know.
     
  13. 2door

    2door Moderator

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    re: The Basics, Port & Polish and Port Matching

    John the Great is absolutely correct in his advice to leave the walls of the intake ports slightly rough. The marks left by the grinding stone or burr is enough. Do not polish to a mirror finish. Doing so will have the opposite effect that one might assume. Proper fuel atomization can not occure across an extremely smooth surface. This is not my opinion but was proven years ago in drag racing and other motor sports.
    That being said, port matching can be beneficial but I believe it might be wise to inform the great unwashed who might try it that they should not expect great performance increases. The expectations of noticible power increases, given the amount of work involved, will not be what some assume. Agreed that anything you can do to 'help' these little engines will be good but I just don't want to see some poor inexperienced dude tear into his otherwise good running engine with the assumption that he's going to set land speed records when he's finished. I think it might be wise to stress that in most cases the benefits will be engine longivity and smoothness as opposed to huge or even noticible power increases. One other item we might want to pass along to newbies contemplating these modifications is the fact that many engine suppliers will not honor the warranty if they suspect that an engine has been disassembled. That could be a problem for someone on a limited budget. Just my thoughts. Otherwise, good thread and should reveal some of those deep dark mysteries regarding so-called porting issues.
    Tom
     
    #13 2door, Mar 20, 2010
    Last edited: Mar 20, 2010
  14. foureasy

    foureasy New Member

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    re: The Basics, Port & Polish and Port Matching

    per wikipedia, under cylinder head porting and myths


    The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.
     
  15. Creative Engineering

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    re: The Basics, Port & Polish and Port Matching

    It is, what's known as, the rate of diminishing returns. In other words...a lot of work for very little gain.

    A finely polished port will offer a 3-5% power increase at a cost of much labor. It must be done 100%...there is a fine break point between "good enough", and realizing the 3-5% increase.

    For general purpose use, (even in race circles), most consider it not worth the effort.

    Jim
     
    #15 Creative Engineering, Mar 21, 2010
    Last edited: Mar 21, 2010
  16. BarelyAWake

    BarelyAWake New Member

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    re: The Basics, Port & Polish and Port Matching

    To clarify;

    Polishing a port to a high gloss may not be as effective as a matte, a port & polish won't make yer bike go noticeably faster...

    But gettin' them scabby chunks out sure does help it run smoother ;)
     
  17. foureasy

    foureasy New Member

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    re: The Basics, Port & Polish and Port Matching

    perfect^^^^^
     
  18. BarelyAWake

    BarelyAWake New Member

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    re: The Basics, Port & Polish and Port Matching

    k - sorry 'bout the delay folks, that pesky RL thang keeps intruding heh


    Anyhoo - as I recall yer sittin' there with yer engine all apart and perhaps wonderin' if it was such a good idea. Never fear - trust me when I say there's few engine projects simpler than portin' one of these lil happy time 2smokers FTW

    If you've never shaped aluminum with a Dremel before - I heartily recommend practicing on something you don't care about first, preferably something with a hole not dissimilar to a port as that's the project yer interested in, but anything will do. Dremels are great tools but they have lil quirks like spinning the "wrong" way and spitting bits and sparks into yer face heh, safety glasses are ossum.

    Lets start with the slightly easier exhaust port, all these engines are jus' a lil different so I've no way of telling how bad the castings may be on yours, but the general procedure is the same. The Dremel comes equipped with two different sized sanding drums, grab the lil one and see how it fits in the "corners" of the oval port - it should be smaller than the curve of the port - allowing you to get down into the "corner" without changing the port's shape or galling the sides. If it's too big and hits the sides without touching the inside of the corner - don't use it, you'll hafta do the detail work by hand.

    It's important to start with the hard stuff first, the hard to reach places and corners. That way it's simple enough to match the rest of it to the work you've already done, if you were to do the large flatish sections first - you may well distort the shape when you try to get the corners to match... that's a pretty good rule of thumb with just about any project by the way - be it porting or painting heh

    With such caution in mind, we'll experiment with a milder grit (like 120gt) small sanding drum and setting yer Dremel to a medium speed. You'll want to use as much of the drum's surface as possible by always keeping it parallel to the port - don't tip the Dremel to use just the edge of the drum as you'll dig into the aluminum and leave gouges that will be hard to make flush later. ALWAYS keep the tool moving for this same reason, back and forth, up and down, whatever it takes - just dont grind away at any one place too much... think like brushing your teeth, just slower ofc.

    With nice smooth lateral motions (side to side) clean all four "corners" of the exhaust port till they're smooth but not necessarily perfect, paying careful attention to always keep the sanding drum flush against the port - particularly near the edges as you do NOT want to bevel them even a little. Resist the urge to do the easier "in and out" motion as you'll leave a deep trench, not to mention when hand sanding later - that motion is about all you can do, so lets use the power tool to do the more difficult method first. If the tool just isn't taking enough off - you can increase Dremel speed and/or switch to a coarser grit, but always remember to let the tool do the cutting - don't press hard or "scrub" with it, all that will do is generate heat, load up the drum with galled aluminum, and put deep and irregular scars in the surface that you'll hafta clean up later and defeating the purpose.

    All four "corners" done and lookin' good? Sweet - now switch to the large sanding drum with 120gt and get the "flat" areas, same method as above except this time with more "side to side" movement, again - always keep it moving, even in lil circular patterns as this will help provide a smooth uniform surface, spend even a lil time in one place and you'll get a wavy, irregular face. The larger the drum, the easier it is to get a smooth flat surface, the lil drum just for the hard to reach stuff.

    Don't worry if you've got a deep pit or two - odds are it was just a bubble in the casting and if you try and chase all of those down you'll end up with nothing but a pile of dust for your troubles. There's no "perfect" with these things - if the port is simply clean and smooth that's beautiful and all we're tryin' for.

    Assuming that you cleaned up your mess with no coarser a drum than 120gt - now we finish sand by hand, 320gt works well (400+gt ifn yer crazy), if you've got particularly deep swirls and scratches you may need to start with 220gt or so. Always use a popsicle stick, round pen, or something similar as a sanding block and same as the Dremel - keep it flush with the work surface as not to bevel the edges. Keep a close eye on any "extra" sandpaper as even a lil bit scraping the edge when yer not lookin' will round that edge.

    You'll notice that despite how much you tried to avoid it - the Dremel left lateral scratches simply because of the way it spins. So while your hand sanding try and keep it to "in and out" opposite of the lateral scratching and circular motions - convenient as this is pretty much all you can do with the space yer in.

    I bet that exhaust port is lookin' pretty hawt now - nice and smooth without alla scabs and bumps it usta have... guess what? The intake port is exactly the same job except as I remember the "corners" are too tight to get even the little Dremel sanding drum in there, so sadly - you'll hafta do those by hand using a pen or a sharpie as a sanding block *shrug* I hate not being able to use power tools... but that's just the way it rolls sometimes heh

    Remember - don't press hard and let the tool do the cutting, keep it flush with the surface at all times, and always keep it moving in circular/oval motions whenever possible. Smooth uniformity is what we're after so that's what ya need to get there :D




    As I've now got 10 minutes to get ready fer work, "To be Continued" yet again lol
     
  19. silverbear

    silverbear The Boy Who Never Grew Up

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    re: The Basics, Port & Polish and Port Matching

    Barely,
    Thanks again for teaching us. I'm developing a real game plan and feeling more confident about what to do and how.
    SB
     
  20. TerrontheSnake

    TerrontheSnake New Member

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    re: The Basics, Port & Polish and Port Matching

    Hey has anyone ever tried a "Vortex" fin inside their intake? a small fin or blade inside the intake tube, this has proven effective in large motors, but I have no idea what it could do for a small 2 smoke
     

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