Pretty sure I broke the coil, about to attempt a "plug&play" swap, have a Q on my diagnostics though

[Cerberus]

I wanna be sure I understand / am approaching things correctly here...

This saw was a monster to start, now - w/o a plug firing while pulling that cord - now it lets you pull the cord like "a regular saw" and feels like one (well, if you'd pulled the wire from the spark-plug!)

My confusion/misunderstanding: I went diagnosing a no-spark situation, new plugs made no difference, ordered a coil & about to install it, but while diagnosing I attached my tachometer and pulled and, while it never gave a # of RPM's, it DID 'turn on' and show "0" a couple times! Have never ever seen this lil tachometer say "0"....I would *expect* zero, since I suspect the problem is dead-coil, but am confused how the tachometer can even "turn on" enough to tell me "0" if there's no spark/pulse? Maybe even a dead coil will yield some non-zero?

Thanks a ton for any help, TBH the coil system confounds me the most on a powersaw, how it "has power" to the plug despite no visible source of electrical power!

/Will update shortly on what my 'direct swap' of the coil did, it's almost funny because I realized I don't need it to turn-on to know the swap "did it", I simply need to try starting it and have it tell me "NOPE, try again weakling" like it does when the plug fires (w/o a plug firing, you can pull that cord nice & smoothly, but starting it -- going from 0 to 3k rpm by-hand -- has proven absurdly difficult for this small guy here!!)

 

[Cerberus]

Should note this isn't "a stock '660'" but instead is a custom "build-off" piece, this thing is my baby lol but it's not 'stock' by any means, figured to mention that.... A good deal of important parts are already swapped to Stihl, will do so w/ the coil if this one works but subsequently fails, anyway if it's not the coil I am VERY stuck/confused and at a loss for what to do next, and realize I don't know how to find anyone in my area I'd trust w/ this saw... Have begun calling shops and have a couple "maybe" places, any tips on how to find a reliable/skilled 2-stroke mechanic would be greatly appreciated, i know where I can ship the saw but realize I need someone local (at least until I have a 3rd 'big saw'!)

 

[Duce]

I try not to work on Stihls, could you have spun flywheel? Had that happen to more than one, just repaired a 262 that flywheel key sheared off.

 

[Stem]

sounds like a sheared flywheel key

 

[Nutball]

I had a ms193 with dead coil that would still generate power, but not enough to jump a spark plug gap. Shortly before it died, I was tuning it because the mess on the muffler looked like the saw was way too rich. I recently read when reading about plug heat that too much carbon buildup on a plug from running too cold or rich can short the spark plug putting extra strain on the coil. Maybe that's what damaged this 1 year old OEM coil on the 193. Maybe the same is happening to you?

 

[Maintenance Chief]

Make sure your kill wire isn't touching anything else it's not supposed to. The coil replacement is pretty straightforward.
While you have the recoil housing off ,hold the clutch steady and rock the flywheel back and forth, shouldn't be any play.

 

[Cerberus]

Well more weirdness in my testing/fixing here -- I installed a new coil, and something changed (now seemed like it wanted to start!!), but the high compression/hard pulls never came back (although it was pushing-out the decomp valve pin again, at least!), but - more importantly - it just really SOUNDED like it wanted to start!! It even DID give me a "full turn-over crank" on full-choke, I just couldn't get it to start...I did loosen & re-align the new coil, fearing maybe I was outta alignment, but I'm starting to doubt this is a fault of the coil (I'm going to recheck the original coil, verify it was truly dead, I'm unsure if my original diagnosis of no-spark was done with it properly grounded!

I turned-in the Idle about 1/5th turn, when it was sounding like it wanted to start, and this made a noticeable difference on the next couple cranks (but didn't seem to afterwards, although I may've flooded it by then)

Cannot figure out the problem if I've got spark and a good carb, but never heard of this spun flywheel you mention:

I try not to work on Stihls, could you have spun flywheel? Had that happen to more than one, just repaired a 262 that flywheel key sheared off.

While I'll of course google it, could you elaborate on what this is? Never even heard of it :/

Will of course inspect the keyway and take pics, if I need to order a new flywheel I'll order tonight I hate not having this unit working it's my fave saw!!

Re working on Stihl...this is actually the 1st time I've ever opened a Stihl powersaw.....am very very happy with quality and with ease-of-access, and parts-placement, the 660 is a beautiful platform I am eager-AF for my 2nd day using the saw ;D

If I can't resolve this -- and it's looking that way -- I don't have "a chainsaw guy", and all the Stihl-authorized shops are just Ace Hardware and Lowes...there's 2 seemingly-viable options for me, gonna check them tomorrow if the 660 isn't working by then because I can't handle being w/o it any longer lol, but only 1 of the 2 guys is Stihl-authorized, I wonder how much of a difference that'll make when amazon can deliver any part in 2 days...

 

[Duce]

Well more weirdness in my testing/fixing here -- I installed a new coil, and something changed (now seemed like it wanted to start!!), but the high compression/hard pulls never came back (although it was pushing-out the decomp valve pin again, at least!), but - more importantly - it just really SOUNDED like it wanted to start!! It even DID give me a "full turn-over crank" on full-choke, I just couldn't get it to start...I did loosen & re-align the new coil, fearing maybe I was outta alignment, but I'm starting to doubt this is a fault of the coil (I'm going to recheck the original coil, verify it was truly dead, I'm unsure if my original diagnosis of no-spark was done with it properly grounded!

I turned-in the Idle about 1/5th turn, when it was sounding like it wanted to start, and this made a noticeable difference on the next couple cranks (but didn't seem to afterwards, although I may've flooded it by then)

Cannot figure out the problem if I've got spark and a good carb, but never heard of this spun flywheel you mention:


While I'll of course google it, could you elaborate on what this is? Never even heard of it :/

Will of course inspect the keyway and take pics, if I need to order a new flywheel I'll order tonight I hate not having this unit working it's my fave saw!!

Re working on Stihl...this is actually the 1st time I've ever opened a Stihl powersaw.....am very very happy with quality and with ease-of-access, and parts-placement, the 660 is a beautiful platform I am eager-AF for my 2nd day using the saw ;D

If I can't resolve this -- and it's looking that way -- I don't have "a chainsaw guy", and all the Stihl-authorized shops are just Ace Hardware and Lowes...there's 2 seemingly-viable options for me, gonna check them tomorrow if the 660 isn't working by then because I can't handle being w/o it any longer lol, but only 1 of the 2 guys is Stihl-authorized, I wonder how much of a difference that'll make when amazon can deliver any part in 2 days...

Not sure about Stihl set up. Husqvarna has key cast in flywheel, it's a compression fit, if shaft and flywheel are not cleaned and torqued properly, crankshaft being steel will shear key off when it's started. Timing will be off and may still see spark, unless spun loose enough.

 

[Maintenance Chief]

The 660 uses a tiny half moon shaped key to align the flywheel with the coil timing . Sometimes they can shear, which will throw off the timing aka no start.
Your local ace may have a key for a dollar or two and I suggest that you use the oem key from stihl. It has 2 small dimples on it to hold it fast in the slot.

 

[Cerberus]

Well I was wrong off-the-bat, the coil WAS giving spark originally or at least it is now (my initial darkroom test, that I erroneously thought it failed, I was not grounding it properly)

Weird thing though.... When this stopped working, it wouldn't respond (seemed 100% it was coil/power) however today it did full "turn-overs" while choked (2 or 3 times) and, several times, it legitimately sounded like it was going to start!! More of those times were at the end, after I turned-in Idle about 1/5th turn....

So it's not the coil giving spark.....I don't think there's flywheel-bite issues like the shearing mentioned because as-said it sounds like it wants to start, I mean the day the problem happened I would've given fair-plausibility to flywheel shearing because you could pull the starter cord and only feel the resistance of the piston movement, but now it's different as said you can actually get it to "speed up" as-if it's gonna try starting (but it doesn't) am afraid I'm flooding it out....

Gonna have to go check the 2 guys/places I think may be able to help me, go early tomorrow, am very sick of not having this unit working it's my favorite and such a damn shame to have it benched especially when I'm sure it's some small silly thing!

 

[Cerberus]

Make sure your kill wire isn't touching anything else it's not supposed to. The coil replacement is pretty straightforward.
While you have the recoil housing off ,hold the clutch steady and rock the flywheel back and forth, shouldn't be any play.

Kill wire = the thin black wire that goes all the way to the On/Off switch of the unit? I should note that ABSOLUTELY could still be a problem area-- when I put the new coil in, I didn't feel like opening-up the carb area and wiring it in so I simply patched it to the OEM black wire Figured I'd work-backwards if no-spark (but, got spark, so went forth)

It now has the original coil & plug back on it and, with those, it IS now doing the "wanna start" behavior (both full turn-overs when cold & choked, and "wanna start" sounds when pulling w/o Choke....however I should note that the characteristic "hard-to-pull" phenomena has not returned, not even for a second, the starter feels like a heavy version of my 590, not something waiting to snap your wrist which is how this saw should be!)


Will open up the carb-area tomorrow and inspect the remainder of that kill-switch wiring, maybe that was it the whole time....because it's trying-to-start with both coils I know it's not coil or plug or plug-wire, still feels electric though so kill-wire seems last option. My flywheel doesn't have a visible keyway as described before but the 'bite' between starter // engine just "feels proper" (I have to imagine a slipping-flywheel doesn't feel right, this thing feels like it's great & wants to be running, as-if a mystery Off switch has been flipped

 

[Cerberus]

The 660 uses a tiny half moon shaped key to align the flywheel with the coil timing . Sometimes they can shear, which will throw off the timing aka no start.
Your local ace may have a key for a dollar or two and I suggest that you use the oem key from stihl. It has 2 small dimples on it to hold it fast in the slot.

Was I ignorant for thinking "I would never leave my saws at Ace"? LOL! Guess I always figured the guys there are not mechanics they're salesmen....but yeah I mean I'll certainly ask as I know i have a 'good Ace' near me, hopefully he can do that because even if that isn't the problem (again, it feels real solid I don't think there's slippage, woudln't you feel that at least a lil??), the plan is still/always to continuously upgrade the unit as-practical (and certainly anytime a part breaks!) until it's as-reliable as any other saw in the arsenal, even just as-is I'm in love w/ it it's just such a beast it's sad seeing it benched so long, will be searching hard for local help tomorrow if opening the carb area doesn't show wiring-problems (cannot fathom seeing that, but the more I can rule-out the better position I'm in when starting w/ an unknown mechanic yknow, don't want them spending 3x as long so they can rule-out things I already did )

 

[Maintenance Chief]

Also going to the stihl manual threads on here is extremely helpful and gives you a descriptive idea if something is "out of the ordinary " .
The crankshaft is tapered under the flywheel and thays what really holds it still when you tighten it down , so theoretically it could be tight with a sheared key ,but unlikely.

 

[Woodslasher]

Was I ignorant for thinking "I would never leave my saws at Ace"? LOL! Guess I always figured the guys there are not mechanics they're salesmen....but yeah I mean I'll certainly ask as I know i have a 'good Ace' near me, hopefully he can do that because even if that isn't the problem (again, it feels real solid I don't think there's slippage, woudln't you feel that at least a lil??), the plan is still/always to continuously upgrade the unit as-practical (and certainly anytime a part breaks!) until it's as-reliable as any other saw in the arsenal, even just as-is I'm in love w/ it it's just such a beast it's sad seeing it benched so long, will be searching hard for local help tomorrow if opening the carb area doesn't show wiring-problems (cannot fathom seeing that, but the more I can rule-out the better position I'm in when starting w/ an unknown mechanic yknow, don't want them spending 3x as long so they can rule-out things I already did )

I can answer part of that, no, you won’t necessarily feel slippage. I blew the key outta my brother’s 372 and couldn’t really tell except that it acted way too advanced. I’m gonna say @Maintenance Chief may be right, your flywheel could be slipping which is why your saw doesn’t wanna rip the pull cord outta your hand anymore.

 

[Jason628]

I try not to work on Stihls, could you have spun flywheel? Had that happen to more than one, just repaired a 262 that flywheel key sheared off.

I try not to work on husqvarna's

 

[Duce]

I try not to work on husqvarna's

Don't blame you, they have loose screw and bolts all the time. Chainsaws are stupid!

 

[Nutball]

My chinese 660 was trying to pull the cord out of my hand every stroke yesterday unless I really gave it all I got, in which case it would either turn over smoothly, or kick a stale mate on the first stroke. Maybe the flywheel slipped and the timing may now be delayed too much. Enough to fire and sound like it is trying to run, but not enough to make it run or kick back when starting.

Leaning the low speed may just be letting the mix burn faster in compensation for delayed timing.

 

[Jason628]

Don't blame you, they have loose screw and bolts all the time. Chainsaws are stupid!

Can't say that I've ever messed with any pro husky saws. They've all been homeowner type saws. Fiddled with a 455 the other day and got it running better. Gotta test it a bit more to see if it stays running well or it blows up. That thing had the most carbon buildup I've seen in a saw. I filled it full of seafoam and let it sit for a while. Chunks of crap were flying out of the exhaust and hitting my hand. Pulled the screw limiters off and turned the high out another half a turn... my China 660 likes to pop the decomp very easily and jerk the rope out of your hand. Did the same thing to my buddy when I handed it to him. I got an oem one to put in just gotta find it in my mounds of saw and motorcycle and car parts.

 

[Maintenance Chief]

In my builds I use Jonsered or husqvarna decomp buttons, they allow more hold off and don't necessarily pop until run. The vintage big Homelites tthat dont hsve them get rolled over real slow till just past tdc then go time!
Since I store most of my saws in an environment that changes temperature I will pop the decomp down to keep a heat increase from building up and depositing fuel in the cylinder that will make them a bear to fire off after a few months.

 

[smokey7]

Try 3 pulls on choke from atleast 1 day cold not touched. Then use a zip tie loose on the throttle about half throttle so you can slip it off once it starts. No more than three pulls on choke