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Poulan Pro Chainsaw 18" 42cc stalls at part throttle

21K views 10 replies 5 participants last post by  H-D 
#1 ·
I purchased this saw from a wholesaler, it was likely a return. It will start and idle fine but after about 1/3 throttle it stalls, FAST. Like you turned off the switch. I have discovered that this saw uses a type of carb that i've not seen before. It has the choke butterfly at the bottom and the regular butterfly at the top. The top butterfly does NOT open until about that 1/3 throttle mark, then it starts to open. This is when the engine stalls which tells me that it must be running way lean. There is no high and low mixture adjustments.

Is the carb just dirty or is there another problem?

I dont think this saw was really ever used. It was likely returned with this problem. Its way too clean to have ever been used.

Any ideas?
 
#3 ·
Sounds like a search for some documentation is a good place to start, to me anyway. With NO mixture adjustment screws & pretty widely variable ethanol content gas being available, I'd be starting with premium fuel or some which had NO ethanol (marinas around here advertise the stuff). If you can't find any reference materials or web sites pertaining to this saw, I reckon a look in the carb is the first order of business after checking the clunker filter. Fuel line issues from the manufacturer are a possibility as well.
 
#4 ·
I was wrong - there ARE mixture adjustment screws. But they dont have the plastic caps on them so they dont have the slot in them to turn them with the screwdriver. On these small carbs the screw has splines on it and the plastic cap meshes with the splines and turns it. However it does appear that the high speed screw is screwed in all the way, or atleast screwed in alot further than the low side one is. I cant turn the high side screw by finger tho so I am thinking it is screwed in all the way.
 
#6 ·
Ok, it must be the mixture adjustment. I adjusted the screw out with a pair of pliers. Adjusted it out even with the low side screw. Now its WAY too rich, smokes alot and doesnt rev high enough but it WILL run above 1/3rd throttle. I am 99% sure the problem is the mixture adjustment. I just need the special tool to adjust it correctly.

BTW I believe the gas I am using now is 91 octane from a pump labeled "No Ethanol". I dont know how it is in other states but here in Missouri, ALL gas less than 91 octane MUST contain 10% ethanol by law. SO, 91 does not have to contain ethanol, but it is ALLOWED to contain it. So unless its 91 octane and labeled "No Ethanol", I no longer buy it. Not for anything. I am glad I drive a diesel... however even that has been messed with, they took out most of the sulfur which makes it hard on the pumps and injectors in pre-07 diesels. Blah! They need to quit messing with out stuff! Or let them foot the bill for the repairs and upgrades.
 
#9 ·
Torque,

Just an idea - I bought a new hedge trimmer last year that had been sitting on the shelf for a long time. It didn't want to run. Wasn't getting fuel. I pulled the fuel filter out of the tank and blew it out good. Problem solved.

I cannot imagine what was plugging the filter??
 
#10 ·
Theres not really enough meat to be able to cut a slot into the head of the screw. I had thought of doing that too but theres just not enough material there :(

Six, theres plenty of fuel reaching the carb. I can see it in the lines running up to it. It primes real well too which means fuel can flow freely through them.
 
#11 ·
Anyone ever scored a small pair of hemostats from an emergency room excursion? (Yeah, they're aka 'roach clips') An orderly told me that they were ordered to dispose of 'em (weren't 'sposed to let the patients tote 'em off, but I looked like someone who could use them). They are most handy for working with this small fuel line & the clamping feature is extremely useful.
 
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