Not a chainsaw, but...

[thenne1713]

I acquired an echo pb250ln blower that won't start or run. It has good spark, 135 psi compression, and vacuum and pressure check okay. It will sputter and want to run for one or two seconds, but then dies. Sometimes it backfires. I figured carb problem, so I bought a hipa new carb, lines, filter. No difference. Still backfires, sputters, and won't start. Any ideas what I might check next?

FUEL FILTER/ FUEL LINE KIT? Test first dribbling fuel into carb, should start run briefly

 

[MAC 7-10]

Sorry for the wrong info on the Echo pb 250. The pb 250 has the primer bulb on the carb thus no need for check valve in gas line. The Echo pb 210 is the one with the check valve because it has no primer bulb. I have both echo models and got ahead of myself, I was chasing a problem some what like hosocat has on my pb 210 and it was that very little check valve leaking Do you have 3 lines returning to your fuel tank? If you do make sure they are connected properly. Good luck

 

[Dusty dingo]

did you actually look into the exhaust port when you had the muffler off? I've had the exhaust ports nearly blocked off right next to the piston. They do not have a check valve in the fuel tank. They do have a primer bulb, and if the new carb is pulling fuel thru the primer, it should eliminate the fuel issue. Of course, the mixture screws should be played with to ensure the fuel is coming in, back out the screws more, specially on idle screw inside the throttle shaft (barrel style throttle) .The high speed screw is under the primer bulb, they take very tiny flat blade screwdrivers. If it starts to run, that is probably an indication that the timing issue is not the problem. However, the flywheels are keyed to the shaft, and it's not impossible for the keys to have either been damaged or even are missing, if you bought it in that condition. Other than that, as others have mentioned, the coil unit itself is part of the timing, and it could be your problem. Let us know how it goes for you.

 

[Dusty dingo]

did you actually look into the exhaust port when you had the muffler off? I've had the exhaust ports nearly blocked off right next to the piston. They do not have a check valve in the fuel tank. They do have a primer bulb, and if the new carb is pulling fuel thru the primer, it should eliminate the fuel issue. Of course, the mixture screws should be played with to ensure the fuel is coming in, back out the screws more, specially on idle screw inside the throttle shaft (barrel style throttle) . The high speed screw is under the primer bulb. If it starts to run, that is probably an indication that the timing issue is not the problem. However, the flywheels are keyed to the shaft, and it's not impossible for the keys to have either been damaged or even are missing, if you bought it in that condition. Other than that, as others have mentioned, the coil unit itself is part of the timing, and it could be your problem. Let us know how it goes for you.