Chain Won't Spin Freely Periodically (Shindiawa 488)

[lrkellogg]

Hi guys,

So the previous owner of my acreage left behind some chainsaws, one of them a Shindaiwa 488. I rebuilt the carb , and it has run beautifully for a saw that is over 30 years old.

I was down cutting some wood and after about 45 minutes, I noticed that the chain would no longer spin freely upon applying throttle. I popped the throttle 2 or 3 times and it then spun free again for about 5 minutes. Shortly after, it did it again, and this time would work itself free after a few throttle bursts, so I figured I'd better call it a day.

I hauled it up to the shop and took the bar and chain off. The clutch/sprocket seemed to be just fine, the bar tip sprocket was quite difficult to spin, but I could do so by pushing with a flat tipped screwdriver and a bit of effort. I cleaned the channel of the bar and tip sprocket out and there was quite a bit of gunk and wood debris in there. The tip sprocket then spun a bit easier, but still took some effort.

I reinstalled, and started the saw, and the first few pulses of throttle it didn't want to spin, but thereafter, it started spinning freely again.

So, given I'm a complete novice with chainsaws, any suggestions on how to fix?

 

[Bob Hedgecutter]

Okay, probably lots of little things to consider- like drive sprocket or spur getting worn and damaged chain driver links. Worn bar rails and sloppy rail groove. Debris packing into the bar nose sprocket bearing, bearing wear or worn out, bar splaying at tip.
You can try soaking the nose of the bar in a jar of diesel fuel or kerosene- will help wash out any debris, or if the bar has a grease port- soak the tip overnight and use grease to hydraulic out debris and or rust.
Or maybe, its just time for a new drive sprocket, new chain and new bar.

Photos of the offending items will help heaps.

 

[lrkellogg]

I'll try to get some pictures posted tonight or tomorrow.

I will say that I did get the tip of the saw pinched pretty good the day before the chain rotation issue started. I was bucking a fallen 2' diameter tree. Perhaps that has something to do with the nose sprocket not turning without significant effort?

 

[Bob Hedgecutter]

I'll try to get some pictures posted tonight or tomorrow.

I will say that I did get the tip of the saw pinched pretty good the day before the chain rotation issue started. I was bucking a fallen 2' diameter tree. Perhaps that has something to do with the nose sprocket not turning without significant effort?

That will do it, pinched nose sprocket on a cheaper quality laminated bar will likely have damaged something.
Does not take much of a twist to open up one side of the bearing and allow one of the flat balls to pop sideways or out of alignment, or the side cover open up a bit allowing the bearings to tilt and jam.
Need to run freely and true at chain speed of wide open throttle- or you can have major problems- like chain snapping.

 

[lrkellogg]

I pulled the bar and chain off again last night and lubricated the front sprocket with some WD-40. It spins much more freely now. I noticed that there is one small point in the sprocket rotation where it takes slightly more effort to spin, but thought I'd give it a try. I put the chain back on and loosened it up a touch from what I'd had it at, and the saw seems to spin freely now with no issues so far. I probably will get a new bar for it sometime though, but this one doesn't seem to have much slop in it yet, so will try using it for a few more cuts and see. If it acts up again, a new bar will certainly be in order. Thanks again for your input and tips!

 

[Indianawoodburner]

This sounds simple but recently happened to me. Make sure your chain is not too tight (unlikely). Check the groove in your bar and ensure no wood chips are in there binding your chain. This has been my problem 2-3 times.
Hope this helps.