Identical chains, one works one doesn't (.325 NK) - SOLVED

[Hundred Acre Wood]

I've been using the Stihl RS Pro (.325/.050 NK) for a few months now, love this setup on my 034.

Today I took off one chain and put a brand new loop on, tensioned it, moved it by hand and it immediately bound up. Took it apart, cleaned the bar, the mount, the clutch cover, anything that could've been causing the bar to sit funny. Tried again, same results.

Put the original loop back on, works with no issues. Put the second loop on again, binds right up so tight it would damage the saw if I ran it. The spur sprocket is new, the bar is new, the first loop works fine.

The front chain tensioner isn't bent, there's no interference in the bar mount, but somehow it must be "walking" in or out on the spur in a way that's causing it to bind. Not sure what would cause that.

 

[jakethesnake]

You 100 percent sure the chain in the box is labeled correct? Is new sprocket oem or aftermarket? I’ve seen a rim sprocket out of round just enough to cause alternating tight/ slack behavior. Old chain could have enough wear to sorta give Something is wonky with either the chain or new sprocket in my opinion

 

[ammoaddict]

Does the have any tight spots in it? In other words does it flex easily at every rivet?

 

[Hundred Acre Wood]

You 100 percent sure the chain in the box is labeled correct? Is new sprocket oem or aftermarket? I’ve seen a rim sprocket out of round just enough to cause alternating tight/ slack behavior. Old chain could have enough wear to sorta give Something is wonky with either the chain or new sprocket in my opinion

I doubled checked the chain. It's absolutely the same correct pitch and gauge.

The spur sprocket, chain, and bar are all Stihl oem. The sprocket doesn't have any noticeable wobble, but I'm sure it's possible there is some. Nothing is perfectly round.

So far it seems like it's the chain, but I'm not sure how.

 

[Hundred Acre Wood]

Does the have any tight spots in it? In other words does it flex easily at every rivet?

You're thinking the rivets may be binding? I'll look at that.

Edit: A couple links feel quite a bit stiffer than all the others. It's brand new, that didn't even cross my mind. I'll soak it in some oil and try again tomorrow morning. Thanks!

 

[jakethesnake]

Put it on saw super loose. Blip throttle 4 times. Then try turning it by hand. Sounds like a heck of a good theory there @ammoaddict

 

[Wilhelm]

Does the have any tight spots in it? In other words does it flex easily at every rivet?

I second this, too tightly spun link.
I had this often back when I used to purchase Stihl loops at the local dealer.

Maybe even a single wrong gauge DL spun into the loop.

Just because the loop came in a box doesn't mean it didn't got spun at a shop by someone not quite competent.

I once received a loop from the US with a tie strap spun in upside down!

 

[Squareground3691]

Yea either tight rivets , or some of drivers have burrs on them possibly, even thoe new chain ,

 

[Hundred Acre Wood]

Well you guys nailed it. It seems like it was just tight rivets.i wouldn't have guessed that.

Soaked it in fluidfilm overnight, wiped it down, put it on super loose like @jakethesnake suggested, and gave it a few revs. Tightened it up properly, made a few test cuts, works perfectly.

Thanks for the help guys!

 

[ammoaddict]

Well you guys nailed it. It seems like it was just tight rivets.i wouldn't have guessed that.

Soaked it in fluidfilm overnight, wiped it down, put it on super loose like @jakethesnake suggested, and gave it a few revs. Tightened it up properly, made a few test cuts, works perfectly.

Thanks for the help guys!

Glad you got it sorted out.