No start

[Tankie]

I have a Poulan Pro 4218 made byHusqvarna. I just rebuilt the saw putting everything new on it including cylinder, piston, ring, coil, spark plug and carb, fuel lines and primer bulb. . I can choke the saw and it will start and run for a second or so then die upon trying to restart on half or full choke I get nothing, it doesn’t even try to run again unless I just leave it and come back later. It will repeat the same thing. What could be wrong with it?

 

[YWPD]

Hey @Bob Hedgecutter any advice what to check next?

 

[Bob Hedgecutter]

Hey @Bob Hedgecutter any advice what to check next?

Dude- it is a plastic consumer saw- and you are asking ME what next?
I do not play around with Mitre 10 or Bunnings (our Walmart?) plastic saws as a rule- but will give it a crack off the top of my head.
First guess would be one of the fuel lines is running incorrectly in the system- one of the purge bulb lines not running to the correct place.
Next: What caused all those parts to need replacing? Could have a massive air leak somewhere.
Third: Low quality replacement parts ie: Chinese elcheapo carb, some of those you need to be near 3 turns out on adjuster screws to get the saw to run, if it will run at all.

Compression, air/fuel ratio and spark- is all you need for a 2 stroke to run.
Try pouring a thimble full of mixed fuel down the throat of the carb with the air filter removed and the choke open, close the choke and start the saw- if it fires and runs for a few seconds- it is fuel delivery and possibly the incorrect fuel line order thing.

 

[Tankie]

I replaced the cylinder, piston and ring due to misadjusting the carb and then I rebuilt it and put a new carb on just because it wasn’t running right before I burnt it up and then I replaced the coil because somehow I pulled it apart where it connected to the spark plug.
Thanks for the info about the fuel lines. I will try to swap them around.

 

[Bob Hedgecutter]

Okay, go back to the original "fault" and the misadjusting of the original carb.
What caused you the need to be playing with the adjuster screws in the first place?
Did the saw start running then dying for no apparent reason and tuning (playing with the screws) helped it run a bit better for a while and then it burned out the top end?

 

[Tankie]

That is exactly what happened

 

[Bob Hedgecutter]

Then I would be picking a great big old air leak in the system somewhere- loose base bolts, seals around the crank.
Not familiar with the model, but manifold tear if it has one and not a block.
Impulse tube (if it has one) torn.

Most people can get away with tuning out an air leak for a short period of time, until the leak gets that bad the saw wont run, or no amount of tuning corrects the too lean condition and the piston burns up.
Uncorrected, if the saw does start running, I would give it a tank- maybe two and you will be replacing cylinders and pistons again.

 

[Bob Hedgecutter]

Not sure if I can link this here but here is the IPL for one and you can see lots of gaskets and seals between cylinder and carb that are potential air leaks- and the bearing cup seals either side of the crankshaft that I am guessing are much the same as the ones on those horrid wee Husqvarna 41/45's,

https://images.homedepot-static.com/catalog/pdfImages/24/2470e23d-a484-4d9a-adfc-2bb17fd6d798.pdf

 

[jasent]

Death by air leak

 

[Tankie]

Thanks for all the replies. I’m about to trash this saw and buy me a Stihl MA250 or MS251. I really haven’t decided which one yet.