Author Topic: Chainsaw Stalls Out While Reving or Cutting  (Read 920 times)

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Offline BikerBill

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Chainsaw Stalls Out While Reving or Cutting
« on: December 17, 2012, 08:55:50 pm »
I recently acquired a ~25 year old Poulan/Craftsman 2.0 cubic inch 16-inch bar chainsaw.  I do not know the history of this saw.  (The chain was on backward and the oil discharge line from the oil pump to the oil hole on the side of saw was missing.  So it seems someone without much knowledge has messed around with the saw.)  The saw starts after a few pulls.  It idles fine.  But when I try to rev it up or cut with it stumbles, stalls and dies.  Sometimes Iím able to make a cut or two.  Other times I canít do any cutting before it stalls out.  It seems like itís not getting enough fuel. 

Iíve checked the following: 

Air
   Air filter is very clean
   Carburetor mounting are bolts tight
   
Exhaust
   Muffler is clean, no soot on spark arrestor screen
   No restriction in muffler

Ignition
   Plug looks new, very clean
   I get a blue-white spark when I turn the engine over

Fuel
    Fuel filter looks clean (I havenít yet tried bypassing it yet but will do that soon)
    Fuel lines are not spongy
    Carburetor jet needles were a little crudded up so I removed them and cleaned them with throttle body cleaneróno change
    The low speed needle is backed out 1 turn from the seated position; the high speed is backed out 1.25 turns
         
Compression
   ~ 130 psi

What do I check next?

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Offline 660magnum

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #1 on: December 17, 2012, 09:48:56 pm »
It probably needs a metering valve diaphragm in the carb?
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Offline 3000 FPS

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #2 on: December 17, 2012, 11:50:14 pm »
Just as 660Magnum said.  I would get a kit and rebuild the carb and replace the fuel lines.  Put the carb in an ultrasonic cleaner if you have one after you have dis-assembled the everything.  I would not remove the welch plugs leave them in.  If no ultrasonic cleaner then spray it with carb cleaner through every orifice that you can find.
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Offline BikerBill

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I Figured as Much
« Reply #3 on: December 21, 2012, 11:25:45 am »
I thought this was the path I'd end up going down.  I ordered the carb rebuild kit.  I'll post back after I get the kit and have completed the rebuild.  I don't have an ultrasonic bath so I'll do the best with a solvent soak.  That did the trick for my snowblower carb. 

Offline Cut4fun .

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #4 on: December 21, 2012, 01:22:48 pm »
I dont have a ultrasonic either and been lucky and have not had to soak any.  I just use carb cleaner through passages when cleaning.
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Offline 660magnum

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #5 on: December 21, 2012, 01:27:30 pm »
Me too
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That knowledge can live after us... and that "Pays It Forward".
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Offline BikerBill

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #6 on: December 27, 2012, 09:46:29 am »
Hey Cut4fun and magnum660,

Thanks for letting me know I probably don't need to soak the carb in a solvent bath.  Do I need to remove the carb from the engine to rebuild it?  I haven't rebuilt this carb before but it seems like it might be possible. 

Offline 660magnum

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #7 on: December 27, 2012, 10:46:05 am »
I always remove the carb for you have to work on both sides.

The metering diaphragm gets hard so you need to replace it. The atmospheric pressure (outside) of the diaphragm gets sawdust built up on it.

The pump side of the carb has a filter screen under the diaphragm where the fuel goes to the metering valve from the pump.There are compensating chambers on the pump side that also fill up with sawdust. This screen gets filled up with saw dust and must be cleaned out.

So I remove all the sawdust and replace the diaphragms.

On the pump side, the pump diaphragm goes against the main carb body. There are two little flaps that act as check valves that must lay flat against the main carb body where the fuel comes in from the tank and goes out towards the metering valve. Then there is a gasket that goes on before the cover plate.

On the metering valve side the gasket goes on first and then the metering valve diaphragm and then the cover.
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That knowledge can live after us... and that "Pays It Forward".
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Offline 3000 FPS

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Re: Chainsaw Stalls Out While Reving or Cutting
« Reply #8 on: December 27, 2012, 10:59:49 am »
Good explanation by 660magnum.   If you follow those instructions you will be in good shape.
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Offline BikerBill

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« Reply #9 on: January 27, 2013, 09:41:57 pm »
OK, so I rebuilt the carb.  There wasn't a lot of crud in the various chambers in the carb but the filter screen was pretty opaque compared to the new one, so I suspect that was the problem.  I left the Welch plugs alone as suggested by 3000FPS.  I put everything back together and the engine now runs fine.  Thanks for your help with this. 

 

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