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2023/04/01 21:42:11
Novatbird

Echo pb403-h saved from the dump…wont start

I picked up a discarded pb403-h.  It was missing carb and ignition coil.  Tested compression, pretty solid at 110psi.  Put a working carb and ignition coil from another pb403 blower on it.  Emptied some pretty old gas from the tank, refilled with fresh gas.  Checked spark arrest or screen and it was very clean.  Pumped bulb on carb, filled up bulb and pumps fuel back into tank through small line.  Spark plug gapped .026” and getting spark.  Just for extra certainty, i pulled the wire from the kill switch to the coil, but again it is getting spark
 
Wont start….
 
Tried my last resort of starter fluid in both the air cleaner housing to the carb and even a small shot right into the cylinder.  No start.
 
Any suggestions for an amateur mechanic?  Hate to see things wind up in landfills if i can get then running.  Thank you in advance for any help.
 
 
 
6 comments Leave a comment
SRTsFZ6
Check that the flywheel key hasn't sheared.  You can get an "idea" if it's close just by finding TDC with the piston and where the magnet is to the coil.
 
It could have leaky lower seals but try a couple teaspoons of 2 stroke oil down the cylinder (helps seal up the rings) and try starting.  Best to try with the muffler completely off.  You can also inspect the ft of the piston skirt with the muffler off.
 
I don't remember if the coil can be installed backwards, if so, check for that.
 
With the new carb on it, double check the intake manifold is installed correctly and with gaskets... 
You don't what was done so most everything must be checked.
 
.
2023/04/02 08:30:04
Novatbird
Thank you for taking the time to read my post and offering up some help.  I really appreciate it.  Coil can only go one way, i installed it with a small gap the thickness of a thin piece of cardboard.  Plug providing what looks like to be plenty of spark.
 
Questions from the learning novice:
Piston is moving up and down, getting spark from magneto/coil.  Could the flywheel key be sheared?
 
with 110psi of compression, could the lower seals be leaky?
 
I will double check the carb installation.
 
Isn’t it strange that with spark, the starter fluid doesnt even get a pop?
 
thank you again, i appreciate your help.  
2023/04/02 08:38:41
SRTsFZ6
Quote:
Questions from the learning novice:
Piston is moving up and down, getting spark from magneto/coil.  Could the flywheel key be sheared?
 
with 110psi of compression, could the lower seals be leaky?
 
I will double check the carb installation.
 
Isn’t it strange that with spark, the starter fluid doesnt even get a pop? " End quote
 
Obviously, the main internals are fine but yes, the keyway can be sheared.  You don't know the history  of the engine nor the competence of who worked on it last.  
 
Again, the magnet on the flywheel should be very close to the coil when the engine is at TDC (piston as high as it goes)..
 
Not enough compression, a hole/leak in the crankcase will not allow starter fluid to get SUCKED into the crankcase, then pushed up to the combustion chamber. 
 
The added oil temporarily added does often help for the initial start. There should be one carb adjuster screw(not the idle adjustment).  If this adjustment is was out, that'll affect starting.
 
For now, try the oil (couple of teaspoons) and check the position of the flywheel magnet to the coil..
 
.
2023/04/03 08:50:51
SRTsFZ6
Lastly, if it doesn't kick and all looks ok, pull with the throttle wide open,  No choke.
 
Many machines can be loaded up with fuel in the crankcase (not alot, but enough to foul the plug)
2023/04/03 08:53:47
Novatbird
Will be back at it with your advice.  Sounds like some great ideas.  Thank you again in advance. Will keep you posted.  I’d love the get this thing running now even if for just the challenge.
 
2023/04/03 14:18:48
Novatbird
Ok pulled the engine off the backpack frame, pulled the blower fan and then magneto.  no shear of the key.  Magneto in proper position.  Will re-assemble and try the oil trick…..
2023/04/08 20:29:36

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