PRH111 wrote on 12/31/69 at 16:00:07:Hogging out ports by taking away a ton of material is the worst way to port. Good for flow bench numbers and engines that rev to 10,000rpm but not good for low revvers...
You want to port in a manner that is conducive to low speed velocity being maintained. Line of sight is one easy method. Also, if you know a bit about fluid dynamics you can get a rough idea on what areas of the port could use some work the most.
...of course you could have already done all of the empirical testing necessary that validates the claim that the areas most needed to be ported for improved flow happen to be the areas where you cannot port due to intrusive oil passages. In this case why not just polish the exhuast port as much as possible and debur the factory casting errors...its better than nothing.
"Hogging out" ports is not the method that we were planning. Using the "line of sight" idea was. The metal we were discussing is indeed in the line of sight. There is a rather intrusive flat casting part across the top of the exhaust which lies just inside the rather restrictive exhaust outlet....(I wish there was an easier method for posting photos).....and while looking at the lubrication schematic for the engine, I became aware of the possibility that an oil passage is contained in this area....an oil return from the top of the head cover.
I have, infact, polished my intake port. That was easy once I removed the valves. The idea to port the exhaust only came after I installed the freer flowing Raask drag pipe in '03.
Since I normally tear the bike apart during the winter, diving into the exhaust was placed on my '04 to do list.
If you'd like a photo, I'll send it offlist.
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