Motorized Bicycle Engine Kit Forum  

Sponsors



Go Back   Motorized Bicycle Engine Kit Forum > Motorized Bicycle Mechanical Components > Heads and Cylinders

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

Reply
 
Thread Tools Display Modes
  #21  
Old 03-23-2010, 01:17 PM
sportscarpat's Avatar
sportscarpat sportscarpat is online now
Bonneville Bomber the Salt Flat record breaker
 
Join Date: Jun 2009
Location: california
Posts: 1,678
Default re: The Basics, Port & Polish and Port Matching

Just a thought from my fabrication perspective, if a somewhat "standard" configuration can be developed for both the intake and exhaust ports on the cylinder I can easily design and laser cut matching flanges to the final port shape. Each port can have it's own shape, that is, and I can cut the two different flanges. We could then use these flanges as templates on the cylinder. Bolt up the bare flange and grind the cylinder until it matches. I could then supply the exhaust flange to weld to the exhaust pipe. I could also take my current intake design and swedge the manifold tube to match the new intake port shape. You would then be ported from the carb, through the cylinder, and right on out the exhaust pipe. Couldn't get any better than that.
Reply With Quote
  #22  
Old 03-23-2010, 01:35 PM
sportscarpat's Avatar
sportscarpat sportscarpat is online now
Bonneville Bomber the Salt Flat record breaker
 
Join Date: Jun 2009
Location: california
Posts: 1,678
Default re: The Basics, Port & Polish and Port Matching

Maybe I need to put a little more time into understanding cylinder porting, but are you guys porting both the cylinder internal and external port shape, or just the internal shape inside the cylinder?
Reply With Quote
  #23  
Old 03-23-2010, 02:17 PM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

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.

While obv removing material makes it larger, I'm not really getting into oversize porting (true porting) other than suggesting any modification is at the owner's discretion- not to alter it's overall shape and remember to leave enough for proper gasket seating.

There's simply too much experimentation and variables in application to give specifics beyond this basic "cleaning" (carb & manifold type, exhaust system, engine size & manufacture, etc.) - but feel free to do whatever you wish with your engine(s), remember to post any results you achieve or even create a performance thread!

Last edited by BarelyAWake; 03-23-2010 at 02:31 PM.
Reply With Quote
  #24  
Old 03-26-2010, 05:31 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

Well, we've done the cylinder's intake and exhaust ports and that leaves the lower transfer ports... their primary purpose in our HT engines to provide lubrication to the crank's bearings, their size and shape critical for timing: A two-stroke



Because of this and just how difficult it is to actually reach down into them with any sort of power tool bit, we're just gonna leave those alone beyond simply smoothing what you can. Don't get too crazy though and do not increase or alter their size and shape. There's often a casting flash ridge that should be cleaned, but your gonna hafta do that by hand;



Getting to that ridge with any tool is defo a problem, I made a "custom" Dremel bit by extending it's shaft - but you'll need a TIG welder to do it and it's sketchy as it's out of balance and prone to "chatter" (bouncing and skipping). Another method that's somewhat tedious is to take a X-acto knife, wrap the handle with masking tape (prevents cylinder marring) and bend the blade to about a 45 degree angle... be careful when trying to bend the blade and face it away from you - they tend to snap suddenly when doing something as silly as that. If you pick up a cheap "generic" set you'll have better luck as it's not as high a carbon steel and will take a bend. Now you can whittle that ridge down, sure it's slow but the aluminum is soft and it'll get the job done.

Fortunately the rest of the transfer port in the engine case is usually just fine. You can trim the gasket a bit so there's no flap sticking out into the port but other than that I'd leave it alone too;

Reply With Quote
  #25  
Old 03-26-2010, 05:57 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

Alrighty then - back to the easy stuff FTW heh

The stock intake and exhaust manifolds and their gaskets are just plain wrong, up to 1/3 smaller an opening then even the unaltered ports they're essentially a wall with a pinhole in it. The welds are often really sloppy with tons of over-penetration, there's gobs and chunks that need to be ground flush as well. If there's anything to be done to these engines - this step is a must, you can skip all the previous steps if you don't want to tear the engine apart but this really outa be attended to.

This is the stock exhaust, notice how much smaller the opening is than the rest of the pipe - let alone the cylinder port;



If you take the original gasket and take a close look, often there's the outline of the port pressed into it if you've had it put together before - if not simply take a sharpie, paint marker, or pencil and scribble a bunch on the cylinder's port, reassemble the intake/exhaust with the gasket in place and pull it back apart - the shape of the port should now be embossed/outlined on the gasket.

Using the Dremel and the small sanding drum (low/medium speed & 120gt), enlarge the gasket to match the outlined cylinder port;



Take the nicly enlarged gasket, place it over the manifold yer doing and trace the larger opening like this;



This will tell you just how much material you'll need to remove to get it even close to what the port size really is. You're somewhat limited in how much you can open it up without cutting through the pipe or the mounting flange so keep a close eye on it's thickness while yer working by looking at the manifold in profile like this;

Reply With Quote
  #26  
Old 03-26-2010, 06:27 AM
silverbear's Avatar
silverbear silverbear is offline
The Boy Who Never Grew Up
 
Join Date: Jul 2009
Location: northeastern Minnesota
Posts: 8,138
Default re: The Basics, Port & Polish and Port Matching

Barely,
Thanks again for the tutorial. I think I've got a much better understanding now of what this is all about. It sounds like at the very least to do this last part of opening up the gaskets to match the ports and then opening up the manifolds to their gaskets' new configurations. I did this already on the newest engine. Next motor will get taken apart for the fuller treatment. I also found the link to how a 2 stroke works very interesting and for the first time have an inkling of what an expansion chamber is all about. Very cool. Things are so much more fulfilling when we understand what is going on and can picture it in the mind's eye. I am often amused and astonished at the lack of understanding many people demonstrate of the world around them. Heat works in our homes by changing the thermostat. Electricity comes from a little hole in the wall called an outlet. Water comes out of the faucet from somewhere else and goes down the drain someplace. Food in the grocery stores comes in packages with a kind of magical disconnect to having been alive... plants reaching for the sun and water and nutrients... animals who were born and died to feed us. How can we be grateful for what we are given without knowing where it comes from? In the same way I will now be able to see my little China Girl more clearly and better know what's going on as she sings to me on the open road. Many thanks, my friend.
SB
__________________
Someday when I grow up I will probably lose interest in toys with wheels, but until then...
Reply With Quote
  #27  
Old 03-26-2010, 06:43 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

Now that you've got the outline traced it's time to start carving away at it... but this ain't aluminum heh and it's gonna be just a lil bit tougher to deal with. It's also gonna get HOT so a quenching bucket (coffee can w/water or w/e) is a must as is a pair of vice grips or pliers if you've got sensitive fingers... but it's prolly better to just hang on to the thing and dunk it when it's getting hot - this is kinda precision work and pliers are a pain and will mar the surface.

For the weld gobs on the inside of the pipe, I'd use one of the coarser, small grinding cylinders (high speed) to get in there, unlike the ports in the cylinder there's no need for such careful patterns as before, hog it out whatever way is easiest - just be sure not to take too much off and weaken/cut through the pipe.

Once you've got that cleaned up, now we're gonna flair out the opening as much as we can in order to come as close to matching it's port. While you can use that same grinding stone I've found it's somewhat easier to get a nice shape and faster material removal to use the edge of one of the thick cut-off wheels... but this is kinda twitchy and you prolly shouldn't try it unless you've got really steady hands and have used a Dremel a lot before.

Remember - there's no way that yer gonna get the inside diameter of the manifold even remotely as large as the cylinder port and you defo need to leave enough for a good gasket seal, what we're after is just a nice, smooth transition between the two. If ya want a true "high flow" system, yer just gonna hafta build or buy something else as these pipes are just too small. Yet this "flaring" helps a LOT so yer defo not wasting any time doing this.

Once you've "hogged out" the majority of the excess material with the coarse stone/wheel and gotten yer shape you'll wanna smooth it out a bit as it'll be kinda rough with tooling marks and ridges. Even though it's steel - I've found that the sanding drums are far better at smoothing than the finest stone... but ya might go through a couple drums as this is tough stuff. Now ya don't wanna press too hard as you'll generate a lot of heat and might even melt the bit - but the fine grit, large sanding drum is about perfect for this. If you start "inside" the pipe and gently round it out you should end up with a nice transition like these;



At this point ya prolly outa take a flat file and/or belt sander and make sure the flange's surface is flush and smooth for a good gasket seal and I really do recommend making your own gaskets out of a quality gasket material (any good auto parts store, bring in yer old gaskets to size) but other than that - yer done FTW!

Again, for an excellent tutorial on how to tear down and reassemble the engine and it's proper torque ranges - it's all right here in glorious detail thanks to Norm: http://motorbicycling.com/f3/engine-...stand-211.html
Reply With Quote
  #28  
Old 03-26-2010, 06:55 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

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

As for the pics... well, I port and polish my engines as soon as I get them, knowing just how sloppy they can be I've always considered the engine itself a "kit" and this as just needful finishing work. As a result I usually don't take pics and what ones I do have were mostly just taken to help someone out in a PM for some other reason.

In fact I was kinda "lucky" in that I hadn't done anything to the above intake manifold, planning on making my own (I've a CNS carb and the fit is poor) I had cut and rewelded it to change it's angle "just for now" till I can make a new one but hadn't actually cleaned it up any - fortunately for this tutorial... but not so fortunate for my camera as I dropped it in the freakin' quenching bucket yesterday morning as I was workin' on the manifold.

Blarg... well - all's well as it actually dried out fine and seems to work like it always did, I guess ya jus' gotta "suffer for the art" heh



Anyway - should this tut be confusing please just let me know, ask whatever questions you need to - I'll even rewrite the thing if people feel it nessasary
Reply With Quote
  #29  
Old 03-26-2010, 07:13 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
 
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default re: The Basics, Port & Polish and Port Matching

Quote:
Originally Posted by silverbear View Post
Barely,
Thanks again for the tutorial. I think I've got a much better understanding now of what this is all about. It sounds like at the very least to do this last part of opening up the gaskets to match the ports and then opening up the manifolds to their gaskets' new configurations. I did this already on the newest engine. Next motor will get taken apart for the fuller treatment. I also found the link to how a 2 stroke works very interesting and for the first time have an inkling of what an expansion chamber is all about. Very cool. Things are so much more fulfilling when we understand what is going on and can picture it in the mind's eye. I am often amused and astonished at the lack of understanding many people demonstrate of the world around them. Heat works in our homes by changing the thermostat. Electricity comes from a little hole in the wall called an outlet. Water comes out of the faucet from somewhere else and goes down the drain someplace. Food in the grocery stores comes in packages with a kind of magical disconnect to having been alive... plants reaching for the sun and water and nutrients... animals who were born and died to feed us. How can we be grateful for what we are given without knowing where it comes from? In the same way I will now be able to see my little China Girl more clearly and better know what's going on as she sings to me on the open road. Many thanks, my friend.
SB

Whoops! Here I was all tappin' away at the keys and never even saw yer reply silverbear - sorry 'bout that heh


Thanks man, yeah - I dearly love these lil 2smokers for their sheer simplicity, I even love how "raw" and unfinished they are as it gives me stuff to do with my trusty Dremel - the feeling of accomplishment I get from even just a purringly smooth idle perhaps disproportionate... but it gives me a case of the lols every time heh

Another thing about these HT kits is because they are so cheap and simple - there's really not much better as a learning experience for those new to engines to just get one and rip it apart to see what's up. I know most get them with the idea of just bolting it to a bike and vrooming off - but in some ways they're shortchanging themselves and loosing out on a good chunk of the experience, not to mention always wondering why the engine doesn't run as well as others, even not knowing what might be wrong should it break.

I know a first-timer may not get it back together perfectly the first time, that as simple as they are they might break or lose something... but given how cheap just an engine is - who cares? The knowledge gained is worth so much more than the motor, it'll last a lifetime and is a great introduction to how all engines work FTW


Of course... I've a terrible habit of taking everything apart, sometimes this doesn't prove to be as wise a move as it coulda been lol *shrug*

"...where's that blasted springy thingie go anyway o_O dangit..."
Reply With Quote
  #30  
Old 03-26-2010, 01:05 PM
2door's Avatar
2door 2door is offline
Super Moderator
 
Join Date: Sep 2008
Location: Littleton, Colorado
Posts: 16,254
Default re: The Basics, Port & Polish and Port Matching

Geoff,
Not trying to glom onto your tutorial but I was planning on doing one about smoothing intake and exhaust flange welds. Instead of a seperate one I decided to throw it in here where there's already an audience who might benefit from it. After all, the Drermel is all warmed up so might as well kill two birds with one stone, so to speak. Hope you don't mind.
Fastener failure has always been a bug-a-boo with a lot of guys and from experience with the little 2 strokes here's one way to help eliminate a cause.
The weld beads around the pipe and flange on the intake and exhaust manifolds are just too darn big. They often extend into the area of the washers and nuts, or bolts. Torquing the fasteners down in a cocked angle will promote fastener failure and loosening. I think the photos will show better what I'm getting at. The first photo is studs setting in an intake flange and you can see how they do not sit flush due to the washers interference with the weld. I grind that weld bead, using a cut off wheel and stone to give clearance for the fasteners. Hope this explains what I'm saying.
Tom
Attached Images
File Type: jpg Fasteners, 1.JPG (280.9 KB, 539 views)
File Type: jpg Fasteners, 5.JPG (257.6 KB, 494 views)
File Type: jpg Fasteners, 6.JPG (289.3 KB, 559 views)
File Type: jpg Fasteners, 7.JPG (379.3 KB, 542 views)
__________________
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 08:46 PM.


Sponsors

Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
MotorBicycling.com