Article By: Daniel Donley – Pandemonium Custom Choppers – www.pandemoniumc2.com
Originally Published In The February 2013 Issue Of Cycle Source Magazine
Got your engine torn down for an overhaul? Or are you just looking for a little more power? Porting & polishing your cylinder heads or head can definitely increase the power and efficiency of your engine. It’s your most affordable performance upgrade you can do, and do it yourself. This month I am showing you how to do a bowl blend and port clean up on an XS650 cylinder head. The basics I’m showing here can be applied to anything from your sweet bike to your push lawnmower.
Using a valve spring compressor (that I made using a large seat clamp), remove the valve spring keepers, springs and valves.
Pull the valve out slightly and rock the valve side to side in the valve guide. There should be little to no movement here. If there is a lot, you need new guides. If the valve passes the side to side test, the next thing I do is to put one finger over the end of the valve guide while quickly removing the valve. You should hear a slight popping sound; this tells you that your guides are in pretty good shape.
Now that the valves are out of the head, look to see if they are bent or not seating correctly. A nice shiny ring around the valve is a good indicator of all being O.K.
After disassembly of the head, I’ll give it a bath in the parts’ washer, and then on to the blast cabinet to remove all the carbon build-up inside the combustion chamber and ports. Give it a good look over checking for cracks in the head casting around the valve guides and seats. A bowl blend and smooth job is definitely in order here.
Underneath the valve seats are a common problem area, and there’s also rough casting inside the ports. These are the areas that I’m going to be smoothing out.
I use various burrs to clean up the bowls and ports. The fine tooth burrs are used for steel, the coarse burrs are for aluminum. The fine tooth burrs can be used on aluminum heads if use a little cutting oil to keep them from loading up.
I like to use a small die grinder with an inline regulator to control my speed.
I took an old spark plug and knocked out the porcelain and welded a piece of ½” round rod to it.
This head holding tool works great in a vise and lets you position the head at many angles.
I start with the coarse aluminum burrs at low speed in the die grinder. This is the porting stage. Be careful and take your time. Remove only small amounts of material at a time and constantly check your work. What you’re after here is to
blend from the valve seat into the port bowl and then in to the port. Remove just enough material to make these transitions smooth and flowing. Don’t try to redesign the port; the factory made it that shape for a reason. Once I’ve got the ports roughed in with the burrs, I move on to the polish stage of the port and polish job. I polish the ports and bowls to an 80 grit finish with sandpaper rolls in the die grinder at low speed. This will help with the atomization of fuel, and make horsepower. DO NOT make the ports shiny as fuel will puddle and will not atomize, and you will create less power. With time and patience, this is a great way to free up some horsepower. This is a basic overview of cylinder head porting and polishing. If you have any questions please give me a call at 419-576-6812