Forestry workers and loggers know how to adjust the carburetor of their favorite chain saw to keep it running at peak performance far from civilization. Poulan does not cater to them -- the chain saw manufacturer purposely makes it difficult to do a full carburetor adjustment. That's because you can quickly kill your saw by doing the adjustment incorrectly. You can do a basic idle adjustment, though, and that may solve the saw's performance problems.
Basic Tuning Procedure
Most contemporary Poulan chainsaws use a Zama carburetor, but if you have an older Poulan, it may have a Walbro. These carburetors differ in the orientation of the adjustment screws, but you use the same procedure to tune either one. The basic procedure involves adjusting the idle speed with the idle screw, identified with the letter "T," and then, if necessary, adjusting the low-speed and high-speed screws, marked "L" and "H," respectively. On newer Poulan saws, the "L" and "H" screws are protected with tamper-proof covers, and you usually have to purchase a special spline screwdriver to turn them.
Before Making Adjustments
The purpose of the carburetor is to mix fuel and air in the proper ratio to ensure top engine performance, so before adjusting it, ensure the engine is getting the maximum amount of air by cleaning or replacing the air filter. Remove the air filter cover by loosening the retaining nut with your fingers, take out the filter and clean it with soapy water or replace it. While you have the air filter cover off, remove the cylinder cover, pull out the spark arrestor from behind the muffler and clean the spark arrestor screen gently with a wire brush. It should be cleaned every 25 service hours, and if it's dirty, it also hinders air flow.
Adjusting the Idle
The saw must be running to adjust the idle, so replace the spark arrestor and air filter and start the engine. If it won't keep running, turn the "T" screw one full turn in the clockwise direction with a slot screwdriver. This will probably make the engine idle too quickly, so be prepared to turn it the other way as soon as the saw starts. Set the saw on a flat surface and ensure nothing can come in contact with the chain, then start the engine. If the chain turns when the saw is idling, the idle is too fast, so turn it down until the chain stops turning, then find the setting at which the engine sounds best and doesn't stall.
Other Carburetor Adjustments
The safest way to adjust the "L" and "H" screws is to set the engine speed to manufacturer specifications by measuring engine speed with a tachometer as you turn the screws. Since Poulan doesn't want consumers to make this adjustment, the company doesn't include these specifications in product manuals. Seasoned chain saw pros who can identify the optimum engine speed by ear can make the adjustment without a tachometer. Because of the risk of engine damage, though, it may be best to follow the company's advice and take the saw to an authorized service technician or contact the company at 800-554-6723 if you aren't a seasoned pro.