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Heads and Cylinders All about your porting, compression, rings, cylinder and piston modifications to your bicycles engine

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  #1  
Old 03-20-2010, 03:45 AM
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BarelyAWake BarelyAWake is offline
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Default The Basics, Port & Polish and Port Matching

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This thread is essentially a basic primer regarding the cleaning and smoothing of the stock port size and shape and the attempt to match the stock intake and exhaust manifolds to their finished ports as well as possible - the finishing stages overlooked by the manufacturer in the interest of budget, it's also remarkably easy.

but... I gotta apologize for the somewhat... odd way in which this tut was written and the pics in it, I really wasn't planning on makin' a true tutorial - but a coupla peeps asked me to really nicely lol so I hadta get offn my butt and do it

So be sure to jus' keep readin' on and to read it all before ya start rippin' yer engine apart - it's all there and even in order, it's just not all on the first page lol

***For those unwilling to tear down their engine, you may wish to skip to these posts: http://motorbicycling.com/showpost.p...1&postcount=25 & http://motorbicycling.com/showpost.p...3&postcount=27 as the stock intake and exhaust manifolds are really restrictive, their gaskets and mounting flanges way too small - it's an easy & quick fix that should be done regardless if you intend to do the rest of the engine.***

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;



look like this;




Bringin' it to a high sheen instead of a smooth semigloss is up to you

Last edited by BarelyAWake; 06-25-2012 at 04:15 AM.
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  #2  
Old 03-20-2010, 05:08 AM
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bairdco bairdco is offline
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Default re: The Basics, Port & Polish and Port Matching

that first picture looks like some scary prehistoric fish you dredge up from the deep...
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Old 03-20-2010, 05:34 AM
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BarelyAWake BarelyAWake is offline
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Default re: The Basics, Port & Polish and Port Matching

No doubt heh

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




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
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Old 03-20-2010, 05:45 AM
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bairdco bairdco is offline
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Default re: The Basics, Port & Polish and Port Matching

this forum needs a new topic.

"this is how i go fast."

or somethin...
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Old 03-20-2010, 07:50 AM
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silverbear silverbear is offline
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Default re: The Basics, Port & Polish and Port Matching

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Originally Posted by bairdco View Post
this forum needs a new topic.

"this is how i go fast."

or somethin...
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 motorized bicycle 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
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Old 03-20-2010, 08:04 AM
Bikeguy Joe Bikeguy Joe is offline
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Default 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.
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Old 03-20-2010, 08:04 AM
Bikeguy Joe Bikeguy Joe is offline
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Default 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.
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Old 03-20-2010, 08:48 AM
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BarelyAWake BarelyAWake is offline
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Default re: The Basics, Port & Polish and Port Matching

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

To be continued...

Last edited by BarelyAWake; 09-15-2014 at 09:42 AM. Reason: dead links
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  #9  
Old 03-20-2010, 09:33 AM
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silverbear silverbear is offline
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Default re: The Basics, Port & Polish and Port Matching

Excellent!
SB
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  #10  
Old 03-20-2010, 09:43 AM
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Default re: The Basics, Port & Polish and Port Matching

Quote:
Originally Posted by BarelyAWake View Post
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 to share as close to the same size & shape as the ports in the cylinder - "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 as large as possible (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;



look like this;




Bringin' it to a high sheen instead of a smooth semigloss is up to you
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'.
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