[Darrell]

I've successfully adjusted my blower carb in the past, but now nothing works. The choke has three settings - full choke, part choke, then run. It will not start at all on full choke, but will start on the middle setting and will run on the last notch. But it dies immediately when I try to let it idle. Also, when I run it, the motor revs up and down. It kind of oscillates, if that makes any sense.

Any suggestions? Preesh.

 

[gene_stl]

If it won't idle with the choke off it probably is not getting enough fuel. I think my next step with the symptoms you describe would be to remove the jets one at a time and spray carb cleaner through them with the soda straw attachment. If you have to leave a little choke on that is probably the low speed jet.

Before you remove the needle, gently close it all the way and carefully note where it is set so you can at least return to that setting. Then spray the carb cleaner and put it back together. Spray it down the carb throat too where the jets enter.
After doing the low jet try it again and see what if anything changes.

Oscillating and hunting is more common in engines that have rpm governors. You might have the high speed jet set too lean which makes the rpm try to run away and then it starts to stall after it leans itself out. So you might need to fatten that jet up by a couple of fractional turns too. I always found it counter intuitive that small engines have rpm run away (like they do when they run out of gas) as the lean out to the point of stalling. Also as they reach that point the exhaust temperature starts to peak and then drops too but running engines too lean burns up the hot sections more quickly than running rich.

Might be time for a new carb kit or a new carb. If you can reach the fuel lines you can slip them off and spray carb cleaner
through the carb. Make sure you don't leave it in the carb because it is harder on diaphragms and plastic than ethanol. It is essentially paint remover. Does the engine have a primer bulb. Do you feel fuel moving and squooshing when you pump it?
Another thing to check is if there is a clogged in tank fuel filter. These rascals can cause all kinds of mysterious headaches that go away when you replace them.

Is there any diagnostic information to be gleaned from the spark plug. Often it needs to be cleaned and the gap checked. I never replace them. I blast them with carb cleaner and use a brass wire brush to make sure no carbon is left. Then I lay the plug on the cylinder head and pull the starter to confirm I have a nice spark. If you have too much deposit on the plug or it is oily you might have been running too rich. Your symptoms though sound like too lean.

 

[Darrell]

Thank you, Gene.

 

[OutdoorEnvy]

Do what Gene says and I bet it works. If you take the carb off double check that the gaskets don't have any tears or any damage. If they do that will effect the air flow and cause issues as well. Good luck!

 

[gene_stl]

Yes make sure the screws or bolts holding the carb on are tight and compressing the gasket and there are no leaks. You can also spritz starting ether or carb cleaner around the carb while it is running and if it changes rpm and sound it might be sucking air which will make it run too lean and possibly do some of the stuff you mention above. You also can use an unlit propane torch to probe for such leaks. If it starts sucking propane it will change rpm and sound too.