Polishing of Intake and exhaust ports for a XR650L

djebel250 said:

Will a polished port increase air flow.

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Nope.

djebel250 said:

but causes a reduction in turbulance resulting in poor Air/Fuel mixture?

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Nope.

The suface texture of the port has nothing (let me repeat that) NOTHING to do with the mass air flow in the ports on any current model four-stroke. You could glue M&Ms into the front of the port and barely get a blip on a flow bench. The air in the straight part of the port will just slide around them because the air nearest the surface is pretty much stalled anyway. The air travels much faster as you get closer to the center of the port (on round ports) . Porting is done within about 1.5 inches of the valve on either side of it. Anything done to the surface texture farther back up the port is just for looks. The real work of porting is rarely seen by the customers because they tend to get the head back with the valves already installed. So all the cool stuff that really gets a port to move air is hidden.



Don't waste your time. :thumb:

Pantaz said:

Exhaust ports can be fully polished.

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But it does nothing positive for airflow. People routinely polish exhausts in the hope it will eliminate carbon build up. In my experience it fails in that regard as well.
The problem is, in an attempt to get a high polish in the port people often times make the surface of the port wavy which has a measurable NEGATIVE impact on flow. There is no solid evidence that polishing has any positive effect on airflow, but it's easy to measure the changes when the surface gets too wavy. 25 years at the flow bench has taught me that most of what I learned/believed/assumed about airflow while reading hot rod magazines was flat out wrong. :thumb: