Husqvarna 141 chainsaw starting issues

[4rfam]

I have a question about a Husqvarna 141 chainsaw I'm trying to fix for a friend. Sometimes it will start and run good other time it want and backfires through the carb and exhaust. I have replaced the carb with a new one, muffler screen is not stopped up and coil works the spark plug fires. Two thing I noticed first the flywheel has a built in keyway, when I put it on the shaft it has a little play side to side maybe a 1/16th either way before I tighten it down. Second on the outside edge surface of the flywheel it has three magnets side by side. touching them with a screwdriver the center one is very strong and two outside ones are weak. Is that normal or should they be the same. Also we have replaced the cylinder, piston, ring, cam bearings and seals. It also has a new coil , basically it new. built in 2004 compression is 125+. It almost sounds like its out of timing.

Any help I'm lost unless it the flywheel.

 

[dfkrug]

Two thing I noticed first the flywheel has a built in keyway, when I put it on the shaft it has a little play side to side maybe a 1/16th either way before I tighten it down.

Does the flywheel wobble AFTER you tighten the retaining nut?

If so, your problem is probably a leaking crank seal, causing a lean condition. Also, your sloppy crank bearing (which causes the leaky seal) will result in an erratic coil pole gap.

You can test for a leaky seal by pressurizing the crankcase after blocking off the exhaust and intake.

 

[4rfam]

Thanks but as stated I put in new crank bearing and seals, no leaks already tested them. No wobble in the flywheel once tightened

 

[dfkrug]

If you have radial play in the flywheel before tightening, that is not good. Does it look like the cast-in key
has been distorted? Have you tried installation in both extremes of rotation?

Does anything different happen when you use the OEM coil, vs. the new aftermarket one you bought? These
homeowner Huskies have fixed ignition timing of about 25deg BTDC, IIRC.

It is possible the magnets in the flywheel are bad, but that is very rare. I am sure you are tired of throwing
parts at this unit.

One other thing: whenever I buy aftermarket Walbro- or Zama-copy carbs, I always take apart and clean them,
even tho they are new. I often find manufacturing debris in there.