Why does my chainsaw chain not cut well and keep falling off?

Question

For two years now I have a little electric chainsaw that I use in my garden. I use it for small trees/bushes, nothing big. I also use it rarely. Last week I realized that it had become very hard to cut with it, so I took the chain to be sharpened. Today I tried out the sharpened chain and it was indeed day-and-night as to what it used to be. The first tree stump came off easily.

However after that the problems started:

• I already noticed last week that the chain somehow doesn't want to stay tight. After cutting for a minute or two it starts to slack and I need to tighten it again. This was never such an issue before and it only got worse today.
• No matter how carefully I cut and how strongly I hold the chainsaw, the cuts it makes tend to "bend" or "curve". Not sure how to describe it, but basically instead of staying on a single straight plane like it should, the cut starts to curve away. This in turn results in the chain being pulled out of the bar and not cutting anymore. As a result I cannot cut anything thicker than 3-5cm anymore, and even that is an effort.
• The chain also fell off twice today, likely as a result of the previous point.

I'm suspecting that the bar may be to blame, but I cannot see anything obviously wrong with it. Maybe it's bent, but I cannot tell with a naked eye. The sprocket turns freely. The chain runs freely. The oil is where it's supposed to be. The chain is properly tightened according to every guide I could find. There is no obvious damage or wear to the bar.

I did notice that the chain has a lot of wiggle room in the bar. Like, even when tightened, the teeth can wiggle sideways quite a bit. But maybe that was always the case and I just didn't pay attention. It is after all the original bar and the original chain and it's been used without problems for a whole season.

I've taken the chainsaw with me and will try to find a repair shop to show it to in the upcoming week, but perhaps it is something I'm doing wrong? I'm not an experienced chainsaw user...

Answer 1

Sounds like two different issues.

The curving cut is typically a problem of damage to the chain teeth making one side not cut properly. A competent chain-sharpening service would either correct that or tell you you need a new chain if it's beyond fixing. In any case, you can try a new chain and see if that works better, which it should, until you hit a rock or nail or the ground with it. If you hit something while cutting the first stump, that could do it, as it does not take much damage to screw up the direction a chain cuts.

The failure to maintain tension is either a defect of the saw, (or possibly the assembly of the bar onto the saw, where having some dirt or sawdust in the wrong place can screw things up) or you not tightening things down properly once the chain is correctly tensioned - third possibility would be lack of lubrication causing the chain to overheat (which makes it longer.) If you put a clean piece of cardboard in front of the bar nose and run the chain, a bit of oil should fly off the chain (the cardboard is just so you can see it.) You should notice the bar & chain oil needing to be refilled as you use the saw for a while.

One subtle factor you are probably not running into is that when you tension a warm or hot chain, you should loosen the chain when your cutting session ends, so that it does not become excessively tight when it cools. That's unlikely for typical homeowner use.

Likewise, the bar slot can wear out, but unless the oil system is broken, clogged, or otherwise not working, that is exceedingly unlikely in "a whole season" of homeowner use, unless you have been cutting into the dirt (don't do that.)

None of these issues is specific to electric chainsaws.