Husky 440 twisted bent crank maybe

[TheCounty]

Father-in-law had his 440 "borrowed" & returned by a local dirtbag. It was extremely low hrs, ran perfect, & still looks new.
Asked me to look at it, as now he could not start it.
It backfires and immediately jerks pull cord to a stop a revolution or two into the pull.
Flywheel/cast in key and crank key slot in perfect condition. Coil gap, etc right on spec.
Tried another coil, & same result.
Managed to start once with wide open throttle, but when throttle was released it backfired to an abrupt stop.
Other noteworthy item was that 3 teeth in a row on the chain were broken off on its return.
Guessing this idiot hit something hard enough to break 3 teeth off of the chain and this may have twisted the crank and now it is too far advanced.
Thoughts and ideas .
Cheers

 

[Gord404]

lend saws, not- always amazed how a person can return a saw all beat up- that just aint right in my old school books

 

[Old2stroke]

VERY unusual to get a twisted crank. Timing can't be too far off if it starts and runs at all so to verify that the timing is too far advanced you will need a timing light to get an accurate diagnosis. Max advance should be less than 30 deg but most electronic coils will have a retard feature at cranking speeds to bring the timing to much less than that. Need someone to join in and tell you what the timing for that saw should be at cranking speeds.

 

[Marley5]

If the key wasn't sheared I wouldn't expect the crank to be damaged.
Did you pull the muffler and take a peek at the piston.
Heck, that idiot might have straight gassed it or ran it hot in big wood.

 

[TheCounty]

Turns over easy with plug out. Excellent compression with plug in.
Also, key does not hold flywheel, proper torque and taper fit does.
My thoughts are that if drive side jammed to a stop hard/fast enough, then inertia of flywheel & crank on left side may deform crank in motor run direction on flywheel side and thus leaving in an advanced position. Tempted to tear it fully down on a crappy day just for "snicks" (aka 5hits & giggles) but time yaknow.

 

[2StrokeFondler]

Did you reset the carb to default settings? Maybe the guy messed with it.

 

[TheCounty]

Purged fuel system & stripped/cleaned carb. Settings to factory & tried tweaking a bit rich & lean. No difference

 

[Bob Hedgecutter]

I am failing to see a jump from 3 teeth in a row missing- to crank bending.
If he hit metal/rock or something too hard, the cutters broke off- chain kept rotating- end of story. I mean if cranks bent from a pretty sudden chain rotational stop- chain brakes would be causing some issues- right?
Backfires are usually from fuel vapour build up in mufflers igniting.
Raw fuel and or vapours end up in mufflers from flooding or over fuelling issues.
Tried a new coil- how about a new spark plug?

Me, Id be taking the muffler off- checking the piston and then do a full leakdown test.

 

[TheCounty]

Multiple sparkplugs tried. Muffler dry & no sign of fuel at all. Sorry maybe for using "backfire" as a descriptor, flame does not pop out carb but ignition fires beautifully and immediate only piston goes wrong way while you are trying to pull through, thus igniting advanced enough not to let piston go over TDC.
Damn hard on the fingers/arm also. As mentioned, I taped throttle wide open & pulled hard and as fast as I could with bar mounted in vise. It started and screamed wide open, but when throttle was released it slowed & immediately kicked back stalling.

 

[Bob Hedgecutter]

But all this and we still havent done the simple view the piston through the exhaust port?
Sounds like you have thrown enough parts in its general direction- pressure and vacuum testing time.

 

[Automan]

Twisted, I am guessing.
Back off iggy a few thou. and retry.

lawn mowers do it hitting a rock, though usually shearing key first.

 

[SteveSr]

Multiple sparkplugs tried. Muffler dry & no sign of fuel at all. Sorry maybe for using "backfire" as a descriptor, flame does not pop out carb but ignition fires beautifully and immediate only piston goes wrong way while you are trying to pull through, thus igniting advanced enough not to let piston go over TDC.
Damn hard on the fingers/arm also. As mentioned, I taped throttle wide open & pulled hard and as fast as I could with bar mounted in vise. It started and screamed wide open, but when throttle was released it slowed & immediately kicked back stalling.

This saw uses the "generic" Stihl 0000-400-1300 "dumb" ignition module. This module has no retarding feature at cranking speed.

One thing that you might try is to remove the flywheel again, clean BOTH mating surfaces on the crank and flywheel with brake cleaner. While this is apart check the FW CAREFULLY with a magnifier to make sure that the key hasn't been "moved" in a CW (advanced) direction.

If this checks out, put the FW loosely back on the shaft and notice that there will be some amount of rotational play in the FW position. Position the FW full CW and tighten down the nut to the specified torque. This should give you a few degrees less advance which may be enough to help starting.

BTW, does this saw have an Elastostart handle on it?

 

[Bob Hedgecutter]

This saw uses the "generic" Stihl 0000-400-1300 "dumb" ignition module. This module has no retarding feature at cranking speed.

One thing that you might try is to remove the flywheel again, clean BOTH mating surfaces on the crank and flywheel with brake cleaner. While this is apart check the FW CAREFULLY with a magnifier to make sure that the key hasn't been "moved" in a CW (advanced) direction.

If this checks out, put the FW loosely back on the shaft and notice that there will be some amount of rotational play in the FW position. Position the FW full CW and tighten down the nut to the specified torque. This should give you a few degrees less advance which may be enough to help starting.

BTW, does this saw have an Elastostart handle on it?

You might be thinking the wrong brand of 440- think smaller- more orange and consumer.

 

[SteveSr]

You might be thinking the wrong brand of 440- think smaller- more orange and consumer.

Quite right!

BTW, ever seen any Husky coils do weird sh*t like this?

 

[TheCounty]

Popped muffler again. Piston appears pristine. Muffler etc all so near new condition.
Only way to retard ignition is to remove cast in key. Did this very carefully so as not to upset taper fit in any way.
First tried with the flywheel retarded about 8 to 10 degrees. Yes, I thought this was lots but lets see.
Holy crap, about the 5th pull it started. Also thrilled in not trying to rip fingers off or jerk the crap out of my wrist as previously.
With choke and a quick throttle grab I could keep it running at a very fast idle and could blip it to full rev although it was obviously struggling & put this down to the fact I likely over retarded. Back on the bench. Ok, lets try only about 2 to 3 degrees retarded. Started on 2nd or 3rd pull on choke & with quick throttle grap it would rev right up nice. No bad sounds, but on trying to let it idle you could hear it jutter just a bit about every second or two as it seemed to try and stall itself firing too soon. It then stalled. Back on the bench... Ok lets shoot for right in between. Then noticed something bad. Crank was not moving at all. Tried to turn flywheel, but that was not happening. Managed to get it loose but the bottom end is FUBAR . Towel officially thrown in. Will save remains for parts but that is it.
Thanks to all who showed interest & offered help.
Have a great 2025
Cheers

 

[Bob Hedgecutter]

Quite right!

BTW, ever seen any Husky coils do weird sh*t like this?

Nope- but a whole lot weird going on here.

 

[Old2stroke]

Popped muffler again. Piston appears pristine. Muffler etc all so near new condition.
Only way to retard ignition is to remove cast in key. Did this very carefully so as not to upset taper fit in any way.
First tried with the flywheel retarded about 8 to 10 degrees. Yes, I thought this was lots but lets see.
Holy crap, about the 5th pull it started. Also thrilled in not trying to rip fingers off or jerk the crap out of my wrist as previously.
With choke and a quick throttle grab I could keep it running at a very fast idle and could blip it to full rev although it was obviously struggling & put this down to the fact I likely over retarded. Back on the bench. Ok, lets try only about 2 to 3 degrees retarded. Started on 2nd or 3rd pull on choke & with quick throttle grap it would rev right up nice. No bad sounds, but on trying to let it idle you could hear it jutter just a bit about every second or two as it seemed to try and stall itself firing too soon. It then stalled. Back on the bench... Ok lets shoot for right in between. Then noticed something bad. Crank was not moving at all. Tried to turn flywheel, but that was not happening. Managed to get it loose but the bottom end is FUBAR . Towel officially thrown in. Will save remains for parts but that is it.
Thanks to all who showed interest & offered help.
Have a great 2025
Chee

Sure would like to know if that crank was twisted or not

 

[dboyd351]

Well, we went from having a flywheel key (post 1) to no flywheel key (post 5) to back having a flywheel key (post 15).

No wonder he has a twisted crank.

 

[nedsim]

Something that I don't think has been mentioned is that the shock of the chain stopping abruptly can't reach the crank unless that shock is transmitted thru the clutch without slip. Unless the clutch is way oversized relative to the size of the engine, I don't see that happening.

 

[farmhard]

It backfires and immediately jerks pull cord to a stop a revolution or two into the pull.

For my 2 cents of input a backfire is caused by Timing or bad ring, or P&C damage.
I had some Stihl cranks twist and they had tight spots and would occasionally squeak.
If the keyway is good the spark is going past the ring into the crank case to cause the backfire (or the coil is advanced). Most times these saws will almost start when cold and then do nothing until they dry out.
Bent crank should not cause intermittent start IMO.