Starts with choke but will not run when choke is opened to run position. New Plug, New fuel filter, New gas and oil mixture, new primer bulb, Spark arestor in exhaust port is cleaned. Will stay running if choke lever is at the half open position but will die out when throttle lever is activated

clean the screen inside the muffler

hello sir, my machine will only start when pumping primmer bulb or squirting fluid in the carburetor than stops. the fuel line has broken off, in most small carburetors this is a ongoing problem.old fuel will crystallize when left in tank for a long time.plugging up ports, fuel lines, small screen in carburetor.fuel lines will dissolve clogging carb.this is why it will run when the choke is on creating a vacuum to where there is fuel forced in the carb to rum,also the gas will evaporate leaving the oil behind clogging up carb.the thing to do is remove carb. and clean out,replacing gaskets or fuel line if necessary.use carb cleaner to clean out carb.make sure to make note where fuel line go.the fuel filter broke off of fuel line letting debris get in carb plugging it up.the muffler is known to clog up a lot on these machines where they want run. the compression should be 60 to 120 lbs any thing below 60 is junk. when adjusting the carb screws turn in all the way than turnout 1 1/4 turns turn in slow until machine runs also you need to check for spark by removing plug and grounding against engine to check spark, ok.a new spark plug would be a good ideal too , if you are going to make these repairs use new fuel line and filter,hope this helps,any comments welcome,thank you, !!

I would recommend replacing the fuel filter and spark plug. If this is a 2-cycle engine be sure you are using fresh gas with the proper oil mixture. If your engine has a fuel primer bulb be sure to push it several times until you feel resistance before starting and make sure there are no fuel leaks. Failing that you may need to adjust the carb fuel mixture screws after the engine runs long enough to warm up (1-2 minutes). Check your owners manual for other troubleshooting procedures. Good luck.

If this unit has a Zama carb (or even if it's a Walbro) this will help you alot: http://www.zamacarb.com/tipspage.html

Clean the carburetor and replace the spark plug and air filter. Also make sure the oil/ fuel ratio is correct.

my 455 did this also I went and bought a new gas filter new gas and mix. try this you might have some water in your gas,also add some sea foam additive to your gas mixture just about a table spoon to 2.5 gallons of gas

could be but lets try some other things first
On the carb. you have a primer bulb have you pushed that several times and is there gas in the bulb itself?
Are all of your fuel lines intact and not broken or brittle including the primer bulb?
Are you using fresh fuel mixture?
Be sure your stop and run switch is in the run position.
find your air filter and remove the filter itself
then you will be looking at the inlet side of the carb.opening and a orange choke shutter
Take a thimbles full of mixed fuel and pour directly into the carb opening with the choke off( turn trimmer on its side to do this)
now with everything (except for the filter) set to run try to start your trimmer 4 or 5 pulls
does it try to run? runs and shuts off? if so then you have carb. issues
which you can either replace or rebuild
sometimes if you do not want to tackle it yourself then it is less time consuming to replace it
but not cheaper.

hope this helps you some

Stiff usually means good compression. So, pump the fuel bulb, put your foot on the flat in the handle, lock the throttle open using the button on top, set choke all the way out and pull. It should kick after a few pulls. Then close choke half way, and pull until it starts, then push choke all in. If it doesn't start, disconnect spark plug and take it out. Have someone watch while the sparkplug is held against metal engine to see if there is a good spark at the plug. If not maybe needs new coil. look at plug to see if it is wet, ie, gas is getting to it to isolate problem to carburetor.