Carburetor adjustment is an important on chain saws and other two-cycle engines. An adjustment the is as well rich will cause a experienced to smoke, have actually insufficient power, an outcome in added carbon build up and may damages the engine. One adjustment that is also lean will additionally produce inadequate power and also is more likely to damage the engine through lean seizure. The exactly carburetor mediate will permit the experienced to produce maximum power, expand the duty bike of the engine, create minimal smoke, idle smoothly, rev up nicely and give trouble free service.An over well-off carburetor convey is when the proportion of fuel in the combustible air/fuel mixture is so high that the fuel does no burn well. The burn does not produce much heat, so the power stroke is weak. The partially shed mixture is expelled into the muffler and also exits the experienced as smoke. One over rich condition reasons carbon buildup and also will plug the fire screen and also cylinder ports if operation for a period of time. Outside of carburetor adjustments this can additionally be brought about by having actually too lot oil mixed with the fuel, and/or old stale gasoline.A skinny carburetor convey is as soon as the proportion of fuel in the combustible air/fuel mixture is for this reason low the there is not enough fuel to burn. This additionally makes a weak power stroke and also causes the experienced to have actually insufficient power. In addition to low power, a lean condition reasons the cylinder temperature to rise, which frequently leads come seizure. A lean problem also enables for excessive RPM which regularly leads to large end rod bearing failure. Other reasons for a lean running problem include absence of oil in the fuel mix, and when the fuel tank operation empty. Constantly stop a saw before the tank runs totally dry. Be sure to usage the correct gasoline:oil mixture ratio recommended for your chainsaw.

You are watching: How to adjust a carburetor on a poulan chainsaw

Most Chain saw Engines have Three Carburetor Adjusting Screws:1. Idle Speed/Throttle stop – This is the adjustment the controls how much the accelerator valve (butterfly) remains open once the throttle trigger is released. If this adjustment is set too low, the engine will certainly die as soon as the throttle trigger is released. The throttle valve (butterfly) simply cuts turn off the supply of combustible air/fuel and the engine stops. If this convey is collection too high, the high idle speed will reason the centrifugal clutch come engage and also the chain will run. This is a attention condition and should never ever be allowed.2. Low speed Fuel convey (marked together on carb, this is the low speed jet)- This is the adjustment that controls the ratio of fuel in the combustible air/fuel mixture at idle speed. One adjustment that is set too wealthy will reason the engine to fill up and die at idle speed. A mixture that is also lean will starve the engine and cause that to race or surge. Very lean convey will cause the engine come die, too.3. High speed Fuel convey (marked H ~ above carb, this is the high rate jet) – This is the adjustment that controls the relationship of fuel in the flammability air/fuel mixture at cutting speed. It would not be precise to say the this is the most important setting, because every one of these adjustments need to be exact for a witnessed to do its best, yet this is the adjustment the determines how the witnessed runs in the cut. One adjustment the is collection too affluent will not permit the observed to with the RPM level crucial to construct maximum power. Throttle an answer may additionally be sluggish and also the engine would smoke and perform poorly. A mixture the is also lean will allow the engine to with an RPM level wherein bearing failure and cylinder seizure are likely. That will additionally lack power in the cut and also tend come run an extremely hot.The preceding information briefly describes rich and also lean running conditions. It also identifies the three adjustment screws and their function. It have to be listed that part chain saws lack the high speed adjustment needle. These saws have what is called a “fixed jet” which is set from the factory. “Fixed jet” carburetors are offered to prohibit the observed operator from setting the adjustment also lean and also damaging the saw. Unfortunately, they also often prohibit the observed from achieving preferably performance.

Carburetor adjustment ProcedureThe adhering to procedure should be complied with to insure suitable carburetor adjustment:• (1) check the wait filter and clean the if necessary. Adjusting the carburetor with the air filter partially clogged is favor adjusting the carburetor with the choke partly on. If you readjust your saw with a dirty wait filter, the saw will certainly run as well lean once the filter is cleaned.• (2) inspect the muffler and exhaust harbor for carbon build up. Carbon clogging the exhaust harbor or spark arrestor display screen can reason a observed to operation as if the carburetor calls for adjustment. Transforming the carburetor settings with a plugged muffler may result in the saw running come lean once the carbon construct up is cleaned out.• (3) If carburetor mediate is required because of a brand-new or rebuilt carburetor, it is ideal to begin with the fuel adjustment settings one rotate out. This is accomplished by gently screwing the adjusting screws onto their seats and also then backing them out one revolve each. Care must be taken once screwing them onto their seats due to the fact that the seats may be conveniently damaged if the convey screws are seated also hard. This seats room delicate and also if they are damaged, the carburetor needs to be replaced.• (4) check the fuel level. The tank have to be over half full. If the carburetor is adjusted when the fuel tank is virtually empty, the carburetor might be changed too rich once the fuel tank is filled.• (5) start the engine and warm the up. If the saw will certainly idle permit it operation for a few minutes. If it will certainly not maintain idle there is no stalling warm it up by consistently squeezing the throttle, perform not operation the accelerator to wide open. Carburetor adjustments made on a cold engine will be also rich when it reaches common operating temperature.• (5) start by setup the idle speed. Try to set the speed at about 2700 RPM. If you don’t have actually a tachometer, shot to collection the rate so the witnessed idles as high as possible without engaging the clutch. Never collection the idle so the chain runs when the throttle is released. If the saw will not idle, go to the next step.• (6) set the low speed fuel adjustment. Slowly turn in the screw until the engine surges or starves for fuel. Make a psychological note of the position of the screwdriver slot. Now gradually turn the mediate screw out and the engine must run better. Keep transforming the screw until the engine starts to fill up. Do a note of the position of the screwdriver slot and also compare it come the position of the lean adjustment. Now progressively turn in the screw to a place where it idles the best. It have to be about midway in between the rich and lean settings.• click on the attach below and also a WAV sound clip will certainly be loaded right into your browser. What you’ll hear is one idling saw. Gradually we skinny the low speed adjuster by turning it in, till the idle climbs and also it climate starts to die. Then us go rich and hear the saw begin to blubber and the RPM’s drop, nearly to a point where it dies. The optimum setting is in between these two extremes. If you’re readjusted too skinny it’ll run out that gas and also die, or die as soon as accelerated. (Note the a saw changed too skinny on the high can additionally die when accelerated.) If girlfriend think you’ve found just the best spot squeeze the throttle and the saw have to rev up without any type of hesitation or stumbling.

See more: Fraction Calculator: 1 2/3 X 3 1/2 X 1/3 Equals, Fraction Calculator: 1 2/3 X 3 1/2

Adjusting the observed idle WAV

• (7) Go ago to action (5) and reset the idle speed. Chances are that the RPM setting has readjusted since girlfriend optimized the fuel mixture adjustment.• (8) collection the high rate fuel adjustment. Hold the trigger broad open and check the RPM with the tachometer. NOTE: If you execute not have a tachometer, set the RPM level so the the experienced “four cycles” or “blubbers” at large open throttle. Carry out not effort to collection at preferably RPM levels without a tachometer. Setup the convey slightly wealthy will to decrease performance, however reduce the possibility of damages to the witnessed engine.• click the connect below and also a WAV sound clip will certainly be loaded into your browser. What you’ll hear this time is a witnessed being adjusted for full rev. After ~ revving it approximately max RPM and also holding, we adjust the high speed rich, bring about it to slow down and also blubber, developing little power. Then we readjust it lean causing it come sound smoother and then the starts to starve, additionally creating small power and also creating a many heat. As we back it turn off from skinny to well-off again, the sound i do not care slightly rougher. This slightly unstable sound (or 4-cycle sound, together it’s occasionally referred to) is whereby you desire it to be. We prefer to say, as “close” to the smooth as you can gain it, but still simply slightly into the rough.This one is larger than the first, and requires more time come load. Those of you with slow-moving systems or connections may not desire to wait!

Adjusting the Saw full Rev WAV

• check that her low speed adjustment tho works as well as before you changed the high rate jet. Changing adjustments top top one jet will certainly often influence the other slightly. If the acceleration is not as prior to go ago to action 6.• collection the final idle speed. This time dial the idle speed screw ago to the shortest rpm where the saw will certainly idle smoothly without seeming as if it will certainly stall out.• Your observed is properly changed and prepared for work. Why Can’t carbs Be collection When they Are brand-new & Then leave Them Alone?Some civilization wonder why their experienced can’t be changed when it’s new and then not need any other tuning. They don’t understand that saws can’t be set at the factory and stay correctly changed for the life the the saw. The fact is, some manufacturers think the way, too, and have make the efforts “fixed jet” and “semi-fixed jet” carburetors. These species of carburetors have actually never worked well. The factor is the elevation, fuel type, fuel age, humidity, wearing materials on the saw and a host of various other factors cause carburetors to need periodic adjustment. The is additionally helpful to be able to readjust the carburetor because that a range of applications; chainsaws set up on chainsaw mills for instance should have actually their high speed adjustments set rich since of the form of anxiety on the saw.