Experienced gardeners share their insights in answering this question :
Sounds like you may need to check / rebuild carby and check fuel lines and fuel filter , check tank breather as well

but before rebuilding carb make sure compression and spark are up to scratch and muffler is clear then make sure that the crankcases are air tight and have no air leaks from ie base gasket , c/case joints, crank seals , insulator gaskets or manifold boots or carb gaskets

this is important vacuum and pressure operate the carby diaphrams if not enough vacuum
carb wont pump / pickup fuel mix from tank

if air is leaking in the unit will typically be hard to start, or not at all, wont idle , keep stalling
require consistant mixture adjustments, or may even increase its own revs without throttle being applied , and may even run hot , and have low power


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Why would the engine only run while the choke is on or with repeated manual priming? An engine that requires the choking (partial or full) after initial engine warm up is an indication that the engine fuel air mixture system is out of adjustment.
If the carburetor is clogged, it may only work with the choke engaged, which is not a good way to be running your engine. Cleaning the carburetor and replacing some of the internal parts with a new carb kit is a great way to get your carburetor running properly again.
The two most common reasons a chainsaw won`t idle are a blocked air filter and an idle screw out of adjustment. Other possible causes include: Dirty Air Filter. Idle Screw out of Adjustment.
Over time, the spark arrestor can become clogged with soot. If the spark arrestor is clogged, the chainsaw may run stall or run rough. To unclog the spark arrestor, remove it and clean it with a wire brush. You can also replace the spark arrestor.
An engine that will fire and run with the choke closed but dies when the choke is opened likely has debris at least partially blocking the fuel passages in the carburetor. In this condition the closed choke provides enough extra fuel to enter the engine to overcome the lack of fuel flowing through the other passages.
If a motorcycle or ATV only runs with the choke on, it`s because the richer “choke on” mixture is actually closer to the engine`s normal operating fuel mixture than the leaner “choke off” mixture. So when the choke is turned off, the engine gets too little fuel and too much air for it to run and it stalls.
If the filter becomes clogged, not enough fuel will reach the engine for it to run properly. Because your chainsaw will idle, but dies when it is revved up to full power, it means that the filter is only partially clogged; it will allow enough fuel to the engine to run on idle, but not enough to sustain full throttle.
The carburetor might need to be replaced.

It could be damaged or old and no longer functioning. To test the carburetor, remove the air filter, pour a teaspoon of fuel into it, and pull the starter rope. If the engine starts momentarily and then dies, the carburetor is likely why the chainsaw won`t start.

Restricted Fuel Lines

The engine can be suffocated from gasoline when at peak demand for fuel if there is any slight restriction or debris in the fuel lines. The fuel line may be clogged from stale fuel deposits, more reasons to cause your chainsaw to cut out when applying throttle.

It will not damage the engine at all. All that will happen is that it will run richer, thus using more fuel. If you did it for thousands of miles you`d probably end up with more deposits in the engine/exhaust, but even that is easy to sort.
A Poulan Pro chain saw engine needs air as well as fuel in order to produce the proper combustion for firing. An air filter that is dirty has clogged passages which restrict the amount of air that can enter the carburetor. As a result, the fuel-and-air mixture may be too rich, resulting in starting difficulties.
It will not damage the engine at all. All that will happen is that it will run richer, thus using more fuel. If you did it for thousands of miles you`d probably end up with more deposits in the engine/exhaust, but even that is easy to sort.
When your trimmer starts and runs on choke, it could be because the check valve in the gas cap is clogged. Start the trimmer and gently unscrew the gas cap halfway off. Turn the choke off and assess. If the engine is still running, that means the gas cap may be the culprit.
When the automatic choke malfunctions, it can cause the engine to run rough or even fail to start. Common symptoms of an automatic choke problem include the engine not starting, running too fast, or running too slow.

Discover Relevant Questions and Answers for Your Specific Issue

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Why will My weed eater only run with the choke fully on and cant give throttle?
ANSWER : It sounds like the carb needs adjusted. Things can even happen to new weed eaters.

Read Full Q/A … : Poulan

Starts right up on choke. then run inrun position for a minute and have to go back to choke to keep it running ,then it runs fine for a couple of minutes and have to go back to choke and start all over again.
ANSWER : This happens with the cover off, so not the filter.

Read Full Q/A … : Poulan

Will only start and run in choked position, when throttle applied chokes out. If started with out choke and throttle position in low speed will start and run for 10 sec then like it runs out of gas.
ANSWER : I have your solution guaranteed, I fixed mine yesturday remove H L screw plastic caps and on high 11 threads exposed and on the low side 8 threads exposed. removing the plastic caps allows u further adjusting these wear out or move soo just take them things off and you will be rolling

Read Full Q/A … : Poulan

Poulan Pro blower PBV 200 when it runs will only keep running on half-choke. I have had the carb serviced every year by a shop who said its the ethanol thats gumming it up. I switched to Ace synthetic fuel (50:1) and it ran for the first tank, now will not start. Take it back to the repair shop or chuck it? Thanks
ANSWER : I have never used, nor heard recommended Ace synthetic fuel. I do believe in synthetic lubricants, and the fuel may be part of the problem. See if you access the H and L mixture screws on the carburetor and adjust them. Here is how that is done:


Read Full Q/A … : Poulan

Have to run on half choke,just stops if i turn it off.fuel is 25 to 1. thanks alan.
ANSWER : More than likely a small passage way in the carb is clogged. You can try some carb cleaner, but you may need to disassemble the carb and clean it out. Be advised that these passageways are sometimes as fine as a human hair, and almost impossible to clear sometimes. A new carb may be required if it is worth it to you. Sorry.

Read Full Q/A … : Poulan

My pbv200le leaf blower only runs when you keep choke lever about half way on all the time. when the engine warms it will die when you push the choke completely off
ANSWER : Check fuel filter,,lines, then carb.
It may need a carb kit.

Read Full Q/A … : Poulan

Won’t idle ,runs wide open unless you pull choke,solutions?
ANSWER : Maybe a carb overhaul can do the job.

Read Full Q/A … : Poulan

Saw cranks and runs in choke but we the throttle is pressed the saw dies out… I repeated starting saw and got the same results, what can I do to fix the problem?
ANSWER : Its running lean, so we need to look at things that will starve the engine of fuel, it is always best to start with the simple inexpensive things first, remove the filter from the fuel tank, fitted to the fuel hose, and replace, check the fuel hoses from the tank up to the carb for signs of detirioration or leaks, there is also an internal filter in the carb, under the alloy pump cove held with a single screw, once all these things have been checked, you can make an adjustment to the carb if it is no better, unscrew the L and the H screw a quarter turn to richen the mixture.

Read Full Q/A … : Poulan