Critter87
ArboristSite Lurker
It has spark, it has fuel, it has air, it has compression. It won’t even burp when pouring fuel directly into the intake. Scientifically, there’s no reason it won’t fire. Any ideas?
Stumped on Husq 353
- Thread starter Critter87
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Check flywheel key,clean and gap coil.See if its loaded up with fuel, turn idle speed screw up a bit.Pull plug and pull 5-10 times. change plug.
I had a Rancher 55 on my bench with exactly the same. Showed very good blue spark outside of the cylinder. Tried new NGK plug, no go.
Then I took pull start/recoil off and there was a China brand coil bolted up. I ordered a good used OEM Husky coil off eBay for less than $15, installed it with correct gap, (business card thickness), then tighten the bolts down. Put it all back together and BAM! She ran perfectly.
Point is, it may show great spark outside of the cylinder, but not fire enough when under compression or may not spark at all.
I would look for a good used or new OEM Husky coil when you rule out the gap is correct now and remove the kill switch wire to eliminate a wiring problem. Also check the flywheel key has not sheared and the timing is off.
Then I took pull start/recoil off and there was a China brand coil bolted up. I ordered a good used OEM Husky coil off eBay for less than $15, installed it with correct gap, (business card thickness), then tighten the bolts down. Put it all back together and BAM! She ran perfectly.
Point is, it may show great spark outside of the cylinder, but not fire enough when under compression or may not spark at all.
I would look for a good used or new OEM Husky coil when you rule out the gap is correct now and remove the kill switch wire to eliminate a wiring problem. Also check the flywheel key has not sheared and the timing is off.
Flooded.
Critter87
ArboristSite Lurker
Found the problem. Woodruff key somehow sheared off the flywheel. How is that even possible?
It’s almost like the saw I looked at one time that “wouldn’t run” and I immediately noticed when I revived it that it wouldn’t pull over, so upon removal of the recoil I realized the flywheel side of the crankshaft had snapped off flush with the crankcase… how in the world it happened is still a mystery to this day
Backstage
ArboristSite Operative
If it’s like the ones I’ve seen, it’s not a key. It’s an alignment nub.
Either way, it can happen if the flywheel side nut isn’t torqued well. The taper fit and the pressure from that nut is what holds the position.
Corect on all counts. The key is nothing but a positioner and does little if anything to hold the flywheel to the crankshaft. That outside flywheel nut has to be tight as a drum. I generally add an 18" pipe extension to the socket wrench in order to exert enough torque. That works.
I had a 268 with the key sheared. I suspect the saw was revved and the chain brake kicked on.
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I didn't tighten the flywheel nut enough (see service manual torque spec) and I think it sheared when pull starting.
The key is only for alignment and the nut needs to be properly tightened so the taper prevents the flywheel from slipping.
The key is only for alignment and the nut needs to be properly tightened so the taper prevents the flywheel from slipping.
Same here
Maybe the nut wasn't tight enough or maybe someone isn't using the de-comp when starting it..
This is the reason Stihl got away from the solid aluminum flywheel on the 066.
Not using the decomp can lead to flywheel/key failure??
@pioneerguy600 shared a good way to prep the flywheel and crank tapers. Put a film of valve lapping compound on the tapers and lap the two together. Be sure to clean all the lapping compound off both parts and especially the seal.
Even if you don't lap it cleaning parts with scotchbrite will make sure no crud interferes with the tapers mating. If you've not done so many saws to "feel" how tight the nut should be, torque it.
For a spark checker, clean up an old functional spark plug and open the gap up to ~3-4mm. A strong coil will jump that when not under compression. Learned that from old time farmer who did such when checking farm tractors/equipment.
Even if you don't lap it cleaning parts with scotchbrite will make sure no crud interferes with the tapers mating. If you've not done so many saws to "feel" how tight the nut should be, torque it.
For a spark checker, clean up an old functional spark plug and open the gap up to ~3-4mm. A strong coil will jump that when not under compression. Learned that from old time farmer who did such when checking farm tractors/equipment.
Backstage
ArboristSite Operative
That would be an EXTREME case. The pull cord rotates the flywheel directly, which is attached to the engine crankshaft. If the flywheel isn’t firmly secured to the crankshaft, it can put stress on the alignment nub/key.
To sheer that nub in starting process, you’d need some combination of the following:
It’s REALLY cold out
Some rust/gunk in the cylinder/piston
You have a base gasket delete and popup piston (excessive compression for the saw design).
Decompression valve isn’t being used.
AND the flywheel is BARELY secured well enough for normal starting use.
Yea, seemed offhand like the pawls would have to be weak misaligned, or debris or awkward pulling motions, etc. for that to happen.
It does release some of the compression putting less pressure on almost everything, including the flywheel key. I always use them because it puts less pressure on my arm, shoulder, etc.
