Husqvarna 254xp - chain goes loose - help needed

[Square Cutter]

Hi everyone

Got myself a fine Husqvarna 254xp - but after making it run well etc. I can't seem to figure out why the chain comes loose.

The rim sprocket is fine, almost brand new.
Chain is brand new.
Bar is...used but not worn out.
The chain tensioner system, screw, nut and rubber thingy is fine, threads aren't broken on the screw.
I tighten up the chain, and when I turn the chain by hand, is seems tight, at first, but turning it further more it seems loose and then tight again.
When I cut, the chain becomes loose, to a point where I have to retighten.

Any ideas?

Nice glad you found a sweet saw. That's a tough one though and would drive me nuts. The loose and tight is likely the oil pump. Or if the chain had been thrown sometimes the drive links get dented on the tips and would cause tight and loose effect as those thicker drive links scrape on the inside of the bar. I know that sometimes my saws will loosen a little bit but I can loosen the bar nuts and it will go back to the proper tension if it had been jammed hard or pinched. Other times I do have to tighten up a little bit from the chain maybe stretching. I won't run a chain unless it's touching the bar all around. I bought a bunch of used chain that was run once but had just been rocked and run dull quite a bit and noticed a lot of the drive links had dents in them to where they wouldn't want to fit into the bar rails. A good sign someone was running a loose chain and throwing chains. I'd try synching down your bar nuts tighter maybe. The bar shouldn't move unless you jam it hard on something. Maybe mark the bar somehow and see if the bar moves. Maybe the cover is cracked where the nuts are and it comes loose. Maybe the tensioner is finding a way to back out on you. Hard to say. I always pull my bar up and get the bar nuts finger tight and then adjust tension. Then tighten the nuts to hold the bar and pull the chain by hand to make sure it rolls smooth but still touching the bottom of the bar. Then tighten the hell out of the bar nuts because the chain tension can change just by the bar sitting up or down on the studs. I'm sure you've done all that and more but hopefully these ideas help spark up an idea. Good luck!

 

[PEK]

Nice glad you found a sweet saw. That's a tough one though and would drive me nuts. The loose and tight is likely the oil pump. Or if the chain had been thrown sometimes the drive links get dented on the tips and would cause tight and loose effect as those thicker drive links scrape on the inside of the bar. I know that sometimes my saws will loosen a little bit but I can loosen the bar nuts and it will go back to the proper tension if it had been jammed hard or pinched. Other times I do have to tighten up a little bit from the chain maybe stretching. I won't run a chain unless it's touching the bar all around. I bought a bunch of used chain that was run once but had just been rocked and run dull quite a bit and noticed a lot of the drive links had dents in them to where they wouldn't want to fit into the bar rails. A good sign someone was running a loose chain and throwing chains. I'd try synching down your bar nuts tighter maybe. The bar shouldn't move unless you jam it hard on something. Maybe mark the bar somehow and see if the bar moves. Maybe the cover is cracked where the nuts are and it comes loose. Maybe the tensioner is finding a way to back out on you. Hard to say. I always pull my bar up and get the bar nuts finger tight and then adjust tension. Then tighten the nuts to hold the bar and pull the chain by hand to make sure it rolls smooth but still touching the bottom of the bar. Then tighten the hell out of the bar nuts because the chain tension can change just by the bar sitting up or down on the studs. I'm sure you've done all that and more but hopefully these ideas help spark up an idea. Good luck!

Very helpful, I always make sure the tip of the bar is pressed down when I tighten the bar nuts which lifts up the tip of the bar and chain, I know that some say it does nothing but it works for me.

 

[HumBurner]

View attachment 1017821

That lady needs to eat some food.

 

[North by Northwest]

Bob , why split hairs , the point is the chain plate is identified within the pics , so quite evident it is not missing ...don't get so defensive . Also Square & Pioneer brink up some very pertinent cause of chain & clutch & rim sprocket defects that would relate to the op's chain rotation concern . The black plastic insert would the least of my concern , however the tensioner screw back out could easily be verified & then temporarily corrected with an o-ring as suggested or locktite . The chain drive links being tweaked or twisted is a very valid potential cause , as is a worn or tweaked bar . I suppose a new chain & bar or at the very least tested in good repair b&c would be a prudent verification ! Although not a cause , the tipping of the bar to ensure proper retensioning of the chain is something I do also revelant or not lol.

 

[Bob Hedgecutter]

Bob , why split hairs , the point is the chain plate is identified within the pics , so quite evident it is not missing ...don't get so defensive . Also Square & Pioneer brink up some very pertinent cause of chain & clutch & rim sprocket defects that would relate to the op's chain rotation concern . The black plastic insert would the least of my concern , however the tensioner screw back out could easily be verified & then temporarily corrected with an o-ring as suggested or locktite . The chain drive links being tweaked or twisted is a very valid potential cause , as is a worn or tweaked bar . I suppose a new chain & bar or at the very least tested in good repair b&c would be a prudent verification ! Although not a cause , the tipping of the bar to ensure proper retensioning of the chain is something I do also revelant or not lol.

I'm not defensive- just stating fact.
My point was- to give another option as to why and how the bar may not be being clamped sufficiently to hold it in place. The screw tensioner does not hold the bar in place per say- it adjusts the chain tension prior to the bar stud nuts being tensioned- their clamping force hold that adjustment. Bad drive and or nose sprockets usually present in an out of round situation and the chain jumping from tight, to loose to tight again.
A simple check is to put a washer on each bar stud prior to fitting the clutch cover, if that keeps the bar and chain in position- then the clamping force was not sufficient previously.
Another potential cause is the stud threads are partially stripped/stretched- or the stud nut threads are and the clamping force is insufficient.

 

[MartDalb]

Overwhelming amount of replies and help here, thanks to everyone to took their time to write and help out!


I will go through every point made and try to follow up with pictures etc.

 

[MartDalb]

Here is a bunch of pictures, trying to provide "evidence" that the screws, bolts, nuts, etc. are all ok.
It is correct, as noted by @rogue60, that the drum has some clear marks on it, but the rim does not seem loose or have slack.

It is hard to take good pictures of the bar and chains.
The top bar + chain is clearly worn in the end, near the nose.

The lower bar + chain (new chain) is not worn in that same manner, worn sure.
This is the bar + chain I have been using, that gets loose.

 

[MartDalb]

As regarding to "raising" the bar tip/nose when tightening bar nuts, this I also always do.

About the chain, yes it is a "Seagenspezi" chain, made in Germany, never had issues with their chains, on any of my chainsaws.
But it may just be giving away slack from just 10/15min usage.

I have never had it happen this bad though, and I am still confused about the issue with the chain being "tight" then "loose" and "tight" again after turning it around by hand, before cutting.

Something is surely off, and the issue must have been pointed out within all this feedback

I just can't retest before securing that chain adj. bolt/screw.
And I have found a better bar+chain, which is tested and works on my Jonsered 2250s.
It is 1.3mm and not 1.5mm as these bar/chains, but still .325

 

[PEK]

As regarding to "raising" the bar tip/nose when tightening bar nuts, this I also always do.

About the chain, yes it is a "Seagenspezi" chain, made in Germany, never had issues with their chains, on any of my chainsaws.
But it may just be giving away slack from just 10/15min usage.

I have never had it happen this bad though, and I am still confused about the issue with the chain being "tight" then "loose" and "tight" again after turning it around by hand, before cutting.

Something is surely off, and the issue must have been pointed out within all this feedback

I just can't retest before securing that chain adj. bolt/screw.
And I have found a better bar+chain, which is tested and works on my Jonsered 2250s.
It is 1.3mm and not 1.5mm as these bar/chains, but still .325

Silly question, which bar nut do you tighten first, i have always tightened the front one first some say the back, you will get the problem sorted in the end especially with the knowledge and help on this site.

 

[MartDalb]

Bob , why split hairs , the point is the chain plate is identified within the pics , so quite evident it is not missing ...don't get so defensive . Also Square & Pioneer brink up some very pertinent cause of chain & clutch & rim sprocket defects that would relate to the op's chain rotation concern . The black plastic insert would the least of my concern , however the tensioner screw back out could easily be verified & then temporarily corrected with an o-ring as suggested or locktite . The chain drive links being tweaked or twisted is a very valid potential cause , as is a worn or tweaked bar . I suppose a new chain & bar or at the very least tested in good repair b&c would be a prudent verification ! Although not a cause , the tipping of the bar to ensure proper retensioning of the chain is something I do also revelant or not lol.

@North by Northwest
Just went through your text here.

Made me grab the bar, which I had identifed as being "ok".
Tried to take a picture, I hope You can see this, the phone cam is making it look even worse than it is, but....I did NOT see this at first inspection.

Thoughts?
The other side of the bar is, ok'ish, but this side is hardly strait, it is actually really bad.
Never seen this before, would this mess up the chain tension etc.?

Bar is toast, that is for sure.


(edit) added a better picture

 

[MartDalb]

Silly question, which bar nut do you tighten first, i have always tightened the front one first some say the back, you will get the problem sorted in the end especially with the knowledge and help on this site.

I have never had to walk away from this site with any issue not being resolved.

I actually don't really notice which I do first, hmm never thought that would matter, perhaps it does though?

 

[North by Northwest]

Silly question, which bar nut do you tighten first, i have always tightened the front one first some say the back, you will get the problem sorted in the end especially with the knowledge and help on this site.

Doesn't really matter bro , if the chain is tensioned properly with the tip up .

 

[PEK]

Doesn't really matter bro , if the chain is tensioned properly with the tip up .

Just one of my habits I suppose.

 

[North by Northwest]

@North by Northwest
Just went through your text here.

Made me grab the bar, which I had identifed as being "ok".
Tried to take a picture, I hope You can see this, the phone cam is making it look even worse than it is, but....I did NOT see this at first inspection.

Thoughts?


(edit) added a better picture

Camera's can be deceiving , however the 2nd pic seems to indicate a few tweaks in the bar contour . This with a matching chain would result in the binding or grabbing in the bar rail groove that you have previously mentioned . Such bar deformation easily occurs during incidental bar bind or pinch occurrences . However your rim sprocket & bar studs do look functionally sound enough , although perhaps a little worn . A new bar & chain test will confirm brother . A little locktite will secure the adjusting nut adequately for a test !

 

[North by Northwest]

Just one of my habits I suppose.

A good habit none the less , takes up some of the residual slack .

 

[MartDalb]

Camera's can be deceiving , however the 2nd pic seems to indicate a few tweaks in the bar contour . This with a matching chain would result in the binding or grabbing in the bar rail groove that you have previously mentioned . Such bar deformation easily occurs during incidental bar bind or pinch occurrences . However your rim sprocket & bar studs do look sound enough , although perhaps a little worn . A new bar & chain test will confirm brother !

Thanks for this reply!

I'd say that this bendy, ski slope bar is toast.
I did not inspect this one good enough, but I have never seen em this way.
I do get lots of used saws, bars and the likes in my hobby workshop, but wow.... someone has had this in a pinch, more than once.
And just to add, the chain ran smooth in the groove, no sign of "pinch" damage in that part, but....yeah picture speaks for itself.

Excited to test out that other bar and chain now!

 

[cookies]

I would toss that clutch drum and bearing since a chains drivers ate through it, check the crank bearing and its pocket in the case.

 

[PEK]

@North by Northwest
Just went through your text here.

Made me grab the bar, which I had identifed as being "ok".
Tried to take a picture, I hope You can see this, the phone cam is making it look even worse than it is, but....I did NOT see this at first inspection.

Thoughts?
The other side of the bar is, ok'ish, but this side is hardly strait, it is actually really bad.
Never seen this before, would this mess up the chain tension etc.?

Bar is toast, that is for sure.


(edit) added a better picture

Its a banana !

 

[HarleyT]

From the pics shown, those rims look pretty worn. unless those pics are deceiving me. I would pop on a new one.

 

[MartDalb]

I would toss that clutch drum and bearing since a chains drivers ate through it, check the crank bearing and its pocket in the case.

dang, really? even if the rim sprocket sits fine on it?