Throwing chains

[Poley4]

I am having trouble throwing the chain off of my 488. The first day I used the saw it threw the chain off. I have had other saws throw a chain once a while, but this saw has done it to me several times and once today while felling a tree. I try to keep my chain tight enough to where there isn't any sag in the chain on the lower side of the bar, but maybe that isn't tight enough? I am running a 20" bar ( that is what the saw came with) and .325 x .050 chisel chain. I have noticed that while sawing, the chain looks as if it is lifting up on the top side of the bar. Any ideas?

 

[PES+]

Are you sure you have the correct bar for the saw?
Also check closely for and bend in the bar or a bent bar rail

How is the condition of the sprocket?

 

[Poley4]

Pest,
The bar is stamped .325 .050 and is the original bar that came on the saw. I probably haven't run more than 25 tanks of fuel through it since it was new. As for the sprocket, it doesn't show any signs of wear. I've have a new 16" bar for it and was going to try it today to see if be any better but the 2 new chains I have for that length of bar ended up being the wrong gauge, too wide.

 

[IchWarriorMkII]

I might be way off base, but you said it looks like the chain is lifting off the top of the rail, have you cleaned out the the rail of the bar?

Maybe its packed full of junk

 

[PES+]

Another good thing to check Ich

Also check your chain drivers for and bent or deformed pieces

I wonder if Ich might have the answer

If the chains get thrown they almost always get damaged

Also check the bar tip closely for side play or rough rolling

 

[Poley4]

Guys,
This is the 3rd new chain I have used on this saw and try always to clean out the groove with a putty knife and compressed air when changing chains. The chains have all seemed to be seated down in the groove well and I am able to rotate the chain easily.

 

[Gologit]

Checking the bar groove for gunk is the first thing I'd do. If you have your oiler turned all the way up, like most of us do, you can get a buildup of bar oil and sawdust that'll surprise you. Also...if you're limbing or brushing pay particular attention to how you handle the saw. Too many guys go at it Like Zorro...waving the saw all over hell and not meeting the wood square. The times I slipped chains that's exactly what I was doing It can be hard on the chain...and on your body.

 

[dtnodya]

After you tension the chain so that bottom of the chain has no sag, turn the screw another 1/4 turn. That might do the trick. I've noticed that on my saws with longer bars, running the chain with no sag is perfect. On my saws with 16 or 14in. bars, I have to get the sag out and then turn 1/4 (+/-) more for them to run right. Food for thought....

If you're scraping the bar with a putty knife and blowing out with compressed air then the bar should be plenty clean. The front sprocket needs to roll smooth (as already mentioned) ... Only other thing I can think of is that the bar might have a weird spot in it ... Like a spot that's wider than the rest or more narrow so give the rails a close look .. That's all I can think of.

 

[PES+]

Do you have a digital camera?

Pics could get you more suggestions

 

[PES+]

Another thing to check

check the bar mounting plates for any evidence of bottom the tie straps hitting them.

I have seen wrong plates and damaged side covers derail chains like you describe.

Where on the top of the bar do you see the lift off if the rails and how far does it lift?

slight lift is normal

You might also check the clutch bearing

Did you get the saw new?

 

[Poley4]

taking pics

Hey Pest,
I will run up tp the shop and take some pics. Will post them later.

Thanks everyone for the help!

 

[Poley4]

shindaiwa pics

Pest,
Yes, I bought this saw new and the chain, while sawing will raise off of the rails maybe 080" to .100", probably no more. Here are some pics of the saw. If you don't see a picture showing what you need to see, let me know.
Thanks again!

 

[PES+]

I need a shot of the tail of the bar then one on the saw without the chain and cover

An edge shot top and bottom lengthwise would help to look for bow or twist

It looks like as I mentioned the tail is not shaped correctly for that mount OR the bar is slightly bent....see the wear marks on both the top and bottom of the bar plates....they are catching the bottom sides of the chain rivets

Check the tail of the new bar against the used one too and a pic of the new bar on the saw with out chain and side cover would help.

.050 ALWAYS derails a LOT easier than the thicker gauges but this does look like an abnormal problem.

 

[Gypo Logger]

From over here, I see two possibilities of your problem. It may be that your chain is one drive link too long. If so, this brings the tail of the bar too far from the sprocket causing the chain to derail as it enters the bar groove. This can be aggevated by a small tail on the bar and too big of a sprocket.
Try the smallest sprocket available or if you can change over to 3/8 then things may smarten up.
John

 

[sILlogger]

the chain throwing run down

here is what i'd do. clean bar groove. check to make sure none of the bar rails are bent(closed down). have the bar rails been trued up(knocked of the burrs). make sure the bar isn't bent. check out the sprocket to make sure that the tip is alright. make sure the chain isn't kinked(ive had that throw them off before). i had a sprocket tip lose some bearing one time that jammed in the bar groove=reaked havoc on the chain drive links and would make the chain jump off. beyond any of this is out of my expertise

also is the chain a skip or full comp

 

[PES+]

Looks like full comp but it looks like it has a fair amount of damage

 

[sILlogger]

o sorry about that, i didn't look at the pics, my fault, ive ran skip and it is alot more apt to jump than full comp.....i dunno other than what i already posted

 

[PES+]

A good shot Gypo called it looking at the adjuster screw...

I was thrown off by his mention of several chains doing it.

He may have brought the old chain with him to match or the bar may be stamped incorrectly.

 

[Gypo Logger]

A good shot Gypo called it looking at the adjuster screw...

I was thrown off by his mention of several chains doing it.

He may have brought the old chain with him to match or the bar may be stamped incorrectly.

Sometimes I will shorten the chain to such a degree that it requires that the chain,bar and sprocket must be added as a unit, meaning a mere 2 or 3mm exist between the bar and the sprocket. This assumes your adjuster will travel that far. I try to have no more than one tie strap length betweeen B&C
John

 

[PES+]

Sometimes I will shorten the chain to such a degree that it requires that the chain,bar and sprocket must be added as a unit, meaning a mere 2 or 3mm exist between the bar and the sprocket. This assumes your adjuster will travel that far. I try to have no more than one tie strap length betweeen B&C
John

LOL....the old Oregon way....