Will only run if choke is on i cleaned carb.i think it may b the primer bulb.iv tryed changing the lines didnt help

Check that the air filter on carburetor is correctly fitted and that the filter element is not blocked. If the filter does not allow air flow it will affect or prevent engine running and by applying the choke the engine will run but it will be using excessive amounts of fuel.

Hi, OK firstly when you pump the primer bulb the primer bulb pulls fuel from the reservoir and pushes it to the carb then after around six to ten pumps the carb chamber is full and the fuel then goes back to the feservoir. Normally if you have a leak on the fuel line you get air in the priming bulb. Next thing is having primed Put the choke on full and pull the engine over a few times untill you hear it fire. Then depress the throttle and put the choke lever back to normal run position and pull the starter a couple of times untill it starts. Thats a pretty fool proff method on all two stroke machines and I have a few. Hope that is of some help.
Steve

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, !!

Look on the carb for 2 screws side by side. where those screws go into the carb, it will be stamped with an "H" and "L". Open the screw that is next to the "H", counterclockwise about 1/4 turn at a time with the engine running, that should solve it.

Hi There, Check the primer bulb for tare or pin holes. Replace it. Check and clean carb jet it maybe plugged with debree. Also check for spark which you didn't say. Replace with correct plug.
Note; Do not use strong cleaners on rubber seals (O rings and gaskets) They dry up and crack.
If needed use a dabble of grease on seals

Try spraying a little gas where you spray starter fluid. If it runs you may have to install diaphram kit. If it has a choke can get around primer not working.

This is an ongoing issue for users, and rightfully so. Small diameter line out of fuel tank (has filter in-tank on end) connects to the side of the carburetor that has the fuel pump....that is the cover without the hole in it. Other larger diameter fuel line out of tank connects to the longer nipple on the external purge/primer bulb. The bulb "pulls" fresh fuel from the fuel tank to the carb and then out of the carb to itself, where it then pushes any air/old fuel back into the fuel tank. The remaining larger diameter fuel line in this setup goes from the metering chamber (has cover with writing on it and a vent-hole) side of the carburetor to the smaller nipple on the purge/primer bulb. Years ago on 2-stroke trimmers, primers were not even used,...you choked the carb with a slide lever and gravity let fuel enter the carb from above...a few pulls, a "pop"...slide it off of choke and away you went.
If the purge/primer bulb is on top of the carb...small line from carb body to small hole in tank with filter. Larger diameter line goes from the bulb on the fuel pump side of the carb to the larger hole in the fuel tank where the line is held in place with a nylon nipple connector that keeps the line from pulling out of the tank.
Please vote on this solution.

yes,,,,its a dirty carb jet or a blocked carb jet strip the carb and blow out all the running jets,dont go poking wire into any of the jets to clean them this could bistroy the jet/s

Check the carb jets, they might be a gummed up!

You cannot flood the engine by pushing the primer bulb too much, unless the hoses are hooked up backwards. The primer does not push gas to the carb, it sucks gas through the carb and returns it to the tank. Top barb on primer is the hose coming from the return side of the carb and the bottom fitting is the hose going to the return fitting on the tank. Look inside tank, it is the one without the filter on it, just a flange with a hole in the center.

If you can see gas and air bubbles moving through the primer and into the tank the hoses are on correctly. If you see bubbles going in the correct direction and then reversing when you remove your finger from the bulb, then the check valves in the primer may be bad. Replace primer.

When you say the primer "gets hard to mash", do you mean it is hard to push in or is it very slow to refill and return to the home position? If it is hard to push in and the bulb is full of gas and the hoses are on correctly then there must be a plug in the line going to the tank or the vent in the gas cap is not working. If it does not return, then it is most likely a plugged filter, plugged line from the tank to the carb, plugged screen inside the carb or a stuck needle valve. The primer is creating a slight vacuum to pull the gas through the carb, which is what the carb does when the engine is running. If there is a full or partial restiction on the supply circuit neither the primer nor the carb can pull enough gas for the engine to run. May need to disassemble carb and clean out any varnish, gunk or plugged ports/jets. Use spray carb cleaner. May want to think about a diaphagm and gasket kit if you do it yourself. If you do not feel confident in taking apart the carb, then take to a repair shop.