MotoMan

Presents:

"Oh No: Homework !! "
(It's Fun Though !!)

In the last issue of Power News, we learned that: 

1: When an intake port is too big to provide the velocity necessary to prevent blowback during the Charging phase, the result is a loss of power at all RPM's. The secret to more power 
is to make the ports smaller.

2: The intake ports in most modern motorcycles are still 
waay too big as they come from the factory !! ...Even for Roadracing use !!


3: Thousands of motorcycles are losing horsepower this winter, 
as many tuners will make their intake ports even bigger !!

Here's a Honda F3 that was professionally 
Flow Bench Ported (enlarged) 
to the MAX !! 

This bike was really, really  slow !!

The head measures well on a Flow Bench, but the engine actually produced Less Power with this ported head than it did with the original stock head !!!

Before:

Stock Yamaha R6 Intake Port

After:

30 Percent Reduced High Velocity 
Yamaha R6 Intake Port 

Before:

Stock Yamaha R1 Intake Port

After:

30 Percent Reduced High Velocity 
Yamaha R1 Intake Port  

The Secret to 
Making Ports Smaller ??


JB Weld Epoxy

Epoxy !!
Epoxy is much easier to work with than welding, and it offers insulation for the incoming fuel /air mixture. (Cooler mixture = denser charge.) 

This product does the best job of expanding & contracting with the engine heat without cracking, or coming loose.

Other products that work well are Loctite "Metal Set" (available in Europe) and Bondo automotive body filler. 

I recommend the JB Weld because it sets up slowly, which can be a real plus when you're first learning this porting technique. 

Recommended Tools

1) Dremel Tool

2) Tool Bits
( Sanding Roll, Stone, Aluminum Cutter)

3) 60 Grit Coarse Sanding Rolls

4) Caliper For Measuring Port Height

5) JB Weld (24 Hour Type)

6) Plastecine Modeling Clay

 7) Dremel Extension Cable

8) Safety Goggles
( Keep Your Eyes !! )

Clean Up First (?)

That's right !! Any traces of oil will ruin the sanding rolls, and make the head an oily mess to work on !! 

So the first step is to wash out all the oil with dishwashing detergent and hot water.

Use compressed air or a blow drier to prevent rust.

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Secure The Head on
The Workbench

 It's critical that the head is secure and stable. It's very easy to ruin a valve seat if the head suddenly shifts while the porting tool is turning at 24,000 RPM !

 Use a 2X4 board to "wheelie" the head into the proper position. 

The clamp-on type light illuminates the ports from the combustion chamber side.
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Get Centered

The end of this sanding mandrel is off center. The result will be inefficient sanding action and chatter marks on the port surface. 

Uneven wear on the sanding roll can cause it to unravel at high speed and possibly damage the cylinder head.

Here, I'm using a marker to find out which way the mandrel is bent. By lightly touching it with the marker while it's spinning, the ink will only show on the "high" side.

Careful ...
By pressing the "inked" side it against the bench, I'm bending the mandrel back slightly 
to perfectly re-center it.

This takes a bit of practice, because it's easy 
to bend the mandrel too much. 

If you have to bend it more than 3 times, 
throw it out and start over with a new one. They get weak from being bent, and can suddenly bend out 90 degrees while spinning 24,000 RPM !!

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Ready To Port !!

Here's the best way to hold the tool. I let the dremel motor hang over my right shoulder, and hold onto the drive cable with both hands.

The bottom of my hands are pushing slightly against the bench to help steady the tool.

Also, notice that I've anchored my right hand with my little finger. This gives the best combination of power and control. With some practice, you can really let the sanding roll "torque" into the metal without losing control.

Use a griding stone to grind the steel valve guide.
Many newer models' valve guides are already flush, so you get to skip this step.

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Once most of the steel guide is ground down, use sanding rolls to make the aluminum boss & valve guide flush with the port roof.

Then, finish the entire port surface using 60 grit sanding rolls.

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Rough Finish  /Grooved Floor 

60 Grit (Coarse) Sanding Roll
Use it to remove the fuel residue, and create a rough port surface.

Aluminum Cutter
Use it to score the port floor to secure the epoxy.

Why Not Polish The Ports ??
Doesn't Air Flow Better on a Smooth Surface ???

Remember that the ultimate goal isn't "flow" ... it's POWER !!

The intake port is going to flow both fuel and air. The problem with fuel is that, since it weighs more, it's difficult to keep it evenly mixed with the air as it follows the contours of the port.

Boundary Layer

The next time you drive a car in the rain, notice that when the car is going 60 MPH, the rain drops go up the hood of the car at walking speed. That's because the smooth surface of the car creates what's known as a boundary layer, and the portion of that layer of air that's nearest to the surface is almost still. 

The same thing happens inside an intake port. Except instead of raindrops, it's fuel droplets that will run down the port wall slower than the air. That causes a serious change in the fuel air mixture by the time it reaches the cylinder, ruining much of the engine's potential power. 
Polishing the port walls will ensure that this happens.

The phrase "Port & Polish" always makes me laugh ... I think the idea came from 70's Hot Rod magazines or something. Anyways, the last thing you want to do is polish your ports !!!

Instead, by making a series of rough 60 grit lines that purposely go against the flow, the "boundary layer area" will be turbulent, and the fuel will stay suspended in the air. 

Remember: Rough is Good !!

Here's what the clay is used for !!

It keeps the liquid epoxy from flowing out and onto the valve seats.

Next, set the head up so that the floors of all 4 ports are level. 

On most heads with downdraft ports, the head will have to be "wheelied" as shown here.

Cold epoxy is super hard to squeeze out of the small cap end of the tube !! 

So, to get it all out as easily as possible, I open the JB Weld tubes backwards. Using a razor to cut open the bottom...

Then, I use a vise-grip pliers to squeeze out all the goo onto a sheet of cardboard.

You'll use about 1 package of 2 tubes each (steel & hardener) per port.

Mix up one at a time.

Ying & Yang

Mix It Up !!

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Clean the screwdriver completely, then twirl up a blob as in the photo on the left.

Keep rotating that screwdriver !!! 
Remember: The minute you stop, the blob will drop !!

Application
The idea is to add the epoxy to the deepest point first and then back up. I add the epoxy in "rows". The first row will flow down onto the clay barrier.

It was impossible to get a clear photo as I added epoxy into the port, so I'm demonstrating it here on paper.

To avoid bubbles, start on the left side, and rotate the screwdriver as you "lay down" the epoxy.

Be sure to make the epoxy a little thicker on the sides. 

Then when the right side is reached, twist the screwdriver as you back it away. That keeps the last strand of epoxy from getting out of control.

Preview: The Finished Port.

Don't Miss The Next Issue: 
Finishing The Ports !!