Stihl 064 "jerk" when starting

[Totembear]

I bet that saw was originally had a limited coil and the coil went bad. So they replaced it with an unlimited coil. @Definitive Dave has a good thread on flywheels and coils on the 064. They had so many of em it will make your head spin. Because of the retarding on the CDIC coil they dont get the correct spark at the right time. I bet you if you pull the flywheel and match it up with the coil you will find the 2 incompatable. Like was mentioned before, need the 2 keyed flywheel. Just helped out a friend of mine who was having the same problem and that was the problem. Do a search for it, it is really good and eye opening!!

 

[Yotaismygame]

Sounds like the coil then. Only once have I had a coil go bad and it would fire so early the saw wouldn't run. Would just fire once per pull and that was it.

 

[Totembear]

The CDIC coil was infamous for going bad. Then people didnt know any better and replaced them with unlimited coils that would pull your arm off if you hit it on the right spot. My friend brought it to somebody who was real good with chainsaws too, just he didnt know about the different coil and flywheel combinations that Stihl had on the 064.

 

[HarleyT]

Pay the tech to pull the jug and decarbon the combustion chamber, have a look around, maybe new rings while in there.

Or do it yourself, easy enough to do. A very thin layer of carbon can cause all kinds of trouble. The carbon is on the top of the piston, and the top of the combustion chamber, not building up in the exhaust port like he was thinking.

It kicks the compression ratio exponentially. Well not that much, but by more than you think.

 

[Totembear]

I'd like to see the numbers on his flywheel and a pic of his coil

 

[HarleyT]

So the saw ran good for weeks, and only had a problem when arriving at the dealer?

 

[HarleyT]

Coils don't usually act like that.....

In my experience....

 

[CausticUC]

Pay the tech to pull the jug and decarbon the combustion chamber, have a look around, maybe new rings while in there.

Or do it yourself, easy enough to do. A very thin layer of carbon can cause all kinds of trouble. The carbon is on the top of the piston, and the top of the combustion chamber, not building up in the exhaust port like he was thinking.

It kicks the compression ratio exponentially. Well not that much, but by more than you think.

My initial assessment has shifted since this thread was started; the "ping" or metallic catching/snapping description is now gone. Not so sure it is hanging up in the cylinder.

I know the 064 has a double ringed, windowed piston, however, if it is binding in compression only (no sounds) that does seem a lot like either a timing issue or that the exhaust is being partially blocked/restricted.

I am curious how a coil can cause a compression issue, that is a new one to me.

 

[HarleyT]

My blood pressure gets higher when I go to the doctor. Maybe it is something like that.....

 

[HarleyT]

The thought is that the "yank" would be caused by a coil that was firing on the upstroke.

Which could easily be tested by just unplugging the spark plug wire when pulling the rope, I would think....

 

[HarleyT]

Or just leaving the switch on "off"....

 

[HarleyT]

If it still yanks, you must acquit.....

 

[HarleyT]

But we are trying to diagnose a problem with not much info...

 

[HarleyT]

Recoil stops.

Feels like it’s hitting something, metal perhaps. Has a “ting” sound when it does catch/jerk. It usually did that when I half-assed it...it’s almost like you’ve got to really commit to pulling that chord (when drop starting) and it’d fire up. I’m guessing the same thing is going to happen when I pick it back up.


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This would make one pull the jug and have a look around......

 

[SEAM]

Not uncommon on that model (and the 044...even the 034). I usually pull several times with the switch OFF until the engine turns over a couple of times each pull. That'll give the saw some "priming fuel" to start running on (?? - might be some other reason). I may have to repeat that a couple of times (or more often after prolonged non-use). The most important is to start pulling with the piston at TDT on larger saws.

You can also squirt some fuel (or spray some WD 40) into the carb bore to facilitate starting.

 

[BuckthornBonnie]

Some good advice above. If he (or you) could just take off the recoil and take a pic of the flywheel /coil area, we may be able to help you. There are a ton of coil combinations for the 1122 series and the incorrect pairing would cause that issue. It’s better to know the fw number which may be on the back.

Like Harley said, eliminate other variables (carbon, flooding, bearings if still making a noise).

Coils don’t usually cause these symptoms, but 1122s (064s, in particular) are the exception.

 

[Totembear]

All that we need takes 5 minutes to either rule out the coil or for confirmation that it is the coil. All we need are pics. I'm just saying this is more common with 064s because there was so many different combinations of coils and flywheels.

 

[HarleyT]

Would removal of the plug wire tell anything?

If it was the coil, then pulling it over with the plug wire "unplugged", it shouldn't yank???

 

[Totembear]

Dont know about that? Maybe? The one way that I know of to tell for sure is to look at the coil and pull the flywheel and look at the numbers. Like I said, my friend could get it started, but over time it got worse, the saw wanted to break his shoulder it was kicking back so hard. Nobody could diagnose it. I mentioned the different coil/flywheel combos and all of a sudden you could see the light come on in his eyes. The CDIC coil had a built in retarder. Thats what originally was on the saw. The coil failed as it usually did and someone put an unlimited coil on it. He pulled the flywheel and sure enough he had the limited flywheel.He ran the saw like that for many years. He filed another keyway into the flywheel and it hasnt wanted to break his shoulder. Any other way of diagnosing the problem I'm just unsure of...

 

[HarleyT]

So the hard starting problem got worse over time?