Polishing Ports

[Ironride]

I pulled my carbs off in order to completely tear them down and give them a good cleaning. While the bike was still on my lift bench I started to look closely at the intake boots and intake ports of the head. I was surprised how un-finished the intake ports are on this bike. Let me re-phrase that; I'm surprised how much horsepower this engine can produce with the intake ports being only cast and not cleaned up at all. I will be pulling the head on this soon to do some upper end work and was considering polishing the ports at that time. Has anyone polished the ports on there XS11 and if you have did it make a noticeable difference in the way it starts, runs, or accelerates? Don't get me wrong, I'm not trying to gain a bunch of horsepower. I just figure since I will have the head torn down, now is the time to do it and possibly improve the over all performance of the engine. Thanks.

[capocrimini]

I've never done a port-n-polish (though I've polished off a good port ), but as I have plans to port the heads in a project car, I've read some how-to's. With some differing opinions, I've come accross a general consensus that the intake ports, if polished at all, should be done sparingly maybe only to remove excess flash(or basically just a mild port), because the roughness of the ports helps "fuel suspension" keeping the fuel and air mixture in a better state for combustion. Too smooth surface changes the properties a bit causing incomplete combustion, a rich state, or some other undesirable effects. The validity of the argument is unknown to me, but they make sense. However, removing the flash, reshaping the combustion chambers a bit, and putting a good polish on the combustion and exhaust ports would definately enhance the air flow through your gas powered "air pump." My advice would be to at the most grind on it a little to smooth things down a bit, but not to particularly put a polish on it. I'm no expert, so take this with a grain of salt please!

[chopper]

match the rubbers to the head,thats all you need to do.clever tuners now reckon smaller ports with steps (like an air dam) are the way to go because of higher gas velocity and less blowback

[Ironride]

You two pretty much gave me the answer I was expecting. I think the wisest thing I can do is follow the old rule of thumb; "If it's not broke…don't fix it!" I think I'll just stick to the original plan of cleaning the carbon from the head, valves, and piston tops along with cleaning up the exhaust ports and calling that good. Thanks for your help.