How to Port a Chainsaw

Porting a chainsaw involves altering the chainsaw’s cylinder and muffler so that there is more air/fuel intake into the engine, and more exhaust. Porting makes your chainsaw more powerful allowing you to lean a little bit more on it and cut through denser wood faster.  We have outlined a couple of guidelines on how to port a chainsaw below.

Chainsaws manufactures have to adhere to EPA emissions requirements. As much, modern chainsaws are so choked that hardly get close to their optimal power and speed. Through porting, you can get rid of the choke, and allow your chainsaw’s engine to unleash its full potential.

A perfect porting job can add approximately 25-40% more cutting speed to your chainsaw, without overburdening the engine.

Porting the Cylinder

As mentioned above, the aim of porting the cylinder is to allow more fuel to get into the engine. The simplest way to do that is to remove all the casting flaws that might have been left behind by the manufactures at the factory.

At the factory, the cylinders are made by pouring melded aluminum into molds. The jugs often remain will flaws that quality-assurance overlooks. The flaws can be eliminated using a file or a dremel. A file works better since a chainsaw cylinder is small and has tight spaces.

You’ll need to dislodge the cylinder from the chainsaw and peek inside the jug through the ports. You’ll be able to see the flaws you can eliminate, in order to allow more air and fuel in. Even if you create a fraction of a millimeter of more space, it will make a difference.

The next step is to work on the oval-shaped exhaust port. Try to make the port square by creating some corners on it. The corners need to have sharp edges and not rounded. The edges should be as symmetrical and uniform as possible.

This reshaping expands the exhaust and eliminates any cyclonic effect that limits the exhaust system. You should then push the square port all out towards the muffler can, then open the muffler and ensure the muffler port and the exhaust port match. After you’ve worked on the exhaust port, you will need to port the muffler itself as well. We’ve outlined how you do that below.

Just to be certain, ensure that you check whether the carburetor pushes enough air inside the crankcase. The crankcase has pistons that force air up into the combustion chamber. Ensure the piston ports are clear and will push in as much air as possible.

Cautions While Porting Small Cylinders

Each engine has a maximum amount of fuel and air that it can take. It is, therefore, easy to make a blunder while porting small cylinders. Ensure you take the following cautions, while you port small cylinders.

  • Do not take too much metal away from the bottom of the exhaust port. If you do, the piston will push the exhaust port towards the crankcase as it travels to the top dead center. The effect is the fuel-air mixture getting into the transfer ports and into the exhaust instead of the combustion chamber. Your fuel will be going to waste
  • The same applies to all the other cylinder ports. You should not port the cylinder hole excessively to avoid causing air leaks. Porting the holes too much can cause the piston ring to fall into the port and get damaged as well.

These cautions apply to small cylinders though. Moderately sized cylinders as those on work chainsaws have thicker pistons, and hence no risks of over porting. Either way, while porting, you should get rid of any flows or protrusions on the ports, not increase the diameter of the port.

Porting the Muffler

Porting the muffler reduces or eliminates any exhaust restrictions put in place by the manufacturer. Exhaust restrictions reduce the rate of combustion and cause your chainsaw to lag.  Chainsaws have two-cycle engines that do not require pistons to exhaust.

Any restrictions of the exhaust will, therefore, cause them to lose performance. Porting the muffler ensures your chainsaw runs cooler and gets a boost of approximately ½ HP.  A chainsaw running cooler will most likely last a while longer. Do the following to port the muffler.

  • Port the outlet and make it larger.
  • If the muffler has baffles, get rid of them.
  • Adjust the carburetor

Porting the Outlet

You can enlarge the muffler outlet by drilling it. There are no risks of misalignments in this case. You could drill another outlet port as well. If the engine exhausts better, it will combust more rapidly and hence more power.  Ensure you do not enlarge the outlet port to a point where it doesn’t match with the exhaust port. The best option is to open out the outlet to the same size as the cylinder exhaust port.

Enlarge the hole at small intervals, while experimenting to see how the performance changes. Too big an outlet port will affect the combustion as well. The air/fuel mixture will be escaping before it fully combusts.

You’ll note an increase in the noise level as well, but you should not bank on the noise only. The manufactures might have placed baffles on the muffler to restrict the exhaust as well. You can get rid of them as well.

Adjusting the Carburetor

You need to adjust the speed needle on the carburetor to match up with the new state of the muffler. The needle needs to be a bit richer to balance with the new rate of combustion so that the engine does not burn. You would not want to be buying another engine sooner than you have to.

Ensure you blow the muffler thoroughly to get rid of any metal fillings that might be on it before you put it back on. Even the tiniest fillings could cause damage to the cylinder and pistons.

It is important that you wait for the warranty of the chainsaw to expire before you start porting it. You have to ensure you have the proper tools for porting both the cylinder and the muffler as well. We recommend that you concentrate on eliminating factory flaws, and restrictions, instead of trying to increase the size of the ports. Ensure you know how to port a chainsaw before you open up any chainsaw. You could easily damage your chainsaw if you are not sure of what you are doing.

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