Porting How To . . . Suzuki Wetbike Engines

What Can I Expect?, Why Should I Do It?, Software Says . . . , What Should I Avoid?, A Phased Approach, Now What?

Topic:                  Thought I'd start a thread covering Porting - including some things to watch for. If you want your motor to purr like a kitten, then all you really need to do is to match the aluminum to the steel sleeve. In this case a regular Dremel with the right-angle attachment works fine. For more aggressive work, a porting tool (flexible shaft-style) and 1/4 inch shank burrs (non-ferrous style) are the way to go. Here are some things to watch out for - and various stages of porting.


Here's A Quick Guide to Porting - the Do's and Don'ts

What Can Expect?

That depends on how extensive the port work is, the other modifications to the engine, and rider weight. If you just take the time to match the upper port aluminum casting to the steel sleeve, you'll end up with a motor that runs much smoother. If you go one step further and make sure all of the ports are at the proper heights - you'll end up with a motor that purrs like a kitten.

If you have done other modifications like bigger bores, decking the block, and/or cutting the cylinder head, then you need to know exactly how much to do all of those prior to touching the porting. Then you can port your motor to whatever specifications you are aiming for. There are several good software packages out there that can help.

With any level of changes, you can hope to increase TORQUE. However, you probably won't gain any more top speed unless you have a custom impeller made. 

If it's SPEED you want - porting should only be a small part of the equation.

Why Should I Do It?

If you have the time and DREMEL tool - why not? Again, the easiest to do is the port matching. That's where you grind the aluminum casting back to match the holes in the sleeve (misalignment). You must take care not to change the size of shape of the steel sleeve though.

If your software is pointing you to make changes to the ports, then you "might" see some additional TORQUE. If you go too far, you might end up with LESS POWER.

Software says "X" - is that right?

Not necessarily. Most packages are assuming that you will be running a tuned pipe. Not gonna happen on a wetbike without creating custom ports on side of motor and running a monster pipe.

Also - you need to remember that the ignition on these motors shuts off around the 5500 rpm range.

What Should I Avoid?

Here are a few things to avoid . . . 

a. Friend says that he ported his MX bike and raised the exhaust 2mm - and you should do that to your wetbike. Only works if you replace the ignition, lighten the flywheel, and strengthen the gearbox to handle 7500 rpm or more (where the exhaust port will start working now. And . . . you'll lose power on the bottom end.

b. A shop that will port your motor for either recreational, hot-recreational, or race-only. Without knowing the piston info, the deck height, the piston height relative to the deck, the cc's of the cylinder head, and head squish band info the shop will only be guessing. 

c. Avoid porting cylinders AFTER you have them bored - unless you have lots of experience. Until you get the hang of it, it's just too easy to nick the bore.

A Phased Approach - Do's and Don'ts

Stage 1: Mild cleanup and/or port-matching

  The idea is to use a burr and grind the aluminum back to match the shapes in the steel sleeve. Care should be taken not to alter the shape, angle, or width of the stock ports.

  Don't - Change the roof angle, width or chamfer on the steel.

  Don't - Do any porting work "AFTER" you have the the block bored. Do all porting first, then have your machinist chamfer the ports after boring.

Stage 2: Stage 1 + cleanup of bottom-end

   Pay attention to the size/shape of the barriers to airflow. That is, take some time and knife-edge the webbing (center of all port openings) at the bottom end.

   Take a small grinding bit and reshape the bottom of the steel sleeve so that it now has a smooth/radiused edge (looking for smooth airflow here)

   Try to remove any excess casting flash and/or roughness

   Don't - Try to make any intake ports mirror-smooth. That'll lead to fuel puddling and/or fuel/oil coming out of suspension.

Stage 3: Stage 2 + attention to upper ports

   Pay critical attention to all angles of the ports (sides, roof, angle of entry into cylinder)

   Take Dremel and widen each of the larger transfer ports approx. 1mm on each side

   Widen small transfer port on each side 1/2mm

   Widen the boost ports 1mm on outside (cleanup bridge between them, but watch those angles)

   Pay special attention to far-outside ports and widen to the point that the outer edge is tangent to the bore

   Don't - Go so wild that you sacrifice the bridges (transfer and boost ports)

   Do the Watercross of Texas Modification and "raise" the bottom of the boost port edge approx. 3/4 of an inch. That's a lot of grinding on the iron sleeve and it's best done with grinding wheels. Take your time and get the sides straight.

Don't try the old modification that cuts the tops of the pistons slightly to allow the ports to open sooner (or more fully). Your rings won't last as long and you risk busting the pistons if you detonate.

Stage 4: Hogzilla

   Purchase a porting tool

   Purchase 1/4 in shank carbide burrs (non-ferrous type)

   Use lubricant when cutting (WD-40 or grease)

   Open up bottom-end ports and blend all radiuses

   Work on exhaust flow on upper cylinder. Smooth the boss that encroaches into the airflow. Especially important on upper cylinder - envision exhaust gasses blowing out of the port and traveling down the outside wall. You'll see what needs attention

   Cleanup exhaust flow on lower cylinder

   Make any adjustments to Port shapes/sizes - prior to boring cylinders. Be sure you calculate the proper deck height, cylinder head volume, and Port timing. Wiseco pistons require much more port modification than stock suzukis, but sit at ZERO deck height. 

   Make note of thin area on block and plan on welding-up this spot just to be safe

   Don't - Work using this new grinding tool unless you have a HUGE area for shavings to land. Cleanup with vacuum cleaner when done.

Now What?

You need to do a couple of things once you're done opening-up the ports. Here they are:

a. Make sure all of the upper edges of the port are at the same height. That is . . . make sure the top cylinder is the same as the bottom. Failure to do this will cause a vibration or "buzz" in your motor.

b. Use a sandpaper cartridge roll (or equiv) to smooth out the casting flash and roughen up the port passages. Don't try to make them mirror smooth - but just clean and burr/bump free.

c. Examine the bottom end very carefully and make sure you didn't get the port walls too thin. If so, swing by your welder and get it TIG welded back up.




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