The Forestry Forum

General Forestry => Chainsaws => Topic started by: massmanute on October 19, 2018, 05:01:44 PM

Title: Hard starting chainsaw
Post by: massmanute on October 19, 2018, 05:01:44 PM
I am a fairly new chain-sawer with a gasoline chainsaw, though I have used light duty electric chainsaws to some extent in the past, mostly for chores like pruning/trimming branches.

I have a Stihl MS660. It's not too hard to start from a cold start, but if it is warm (after running a while) it is extremely hard to re-start. Thirty pulls or more and not a sign of starting is not unusual. After the saw is warm I usually have the choke lever set at the warm start settings, but I have tried both the cold start setting and the run setting, and nothing seems to work.

If I let the saw sit a while then it starts with much less difficulty.

In my own naive way I am thinking the engine is flooded, but if so I don't know what to do about it, other than wait.

Any thoughts?

By the way, the application is cutting planks from logs using a ripping chain.

Title: Re: Hard starting chainsaw
Post by: John Mc on October 19, 2018, 06:28:02 PM
Is you are chainsaw milling (cutting planks from logs with a ripping chain), it's likely the chainsaw is getting rather hot. It's possible this is causing vapor lock: fuel vaporizing in places where it's supposed to be still liquid. The vapor in the wrong places can prevent the fuel from getting where it needs to go. When you let the saw sit and cool down, the vapor condenses and the saw will start again. It's often not an issue when the saw is running, since the constant flow of fuel doesn't keep it in one place long enough to get so hot that it vaporizes (though extreme cases can cause the saw to die while running.

A couple of thing to try, in order of increasing complexity:

Let the saw run without a heavy load for a while before shutting it off. This will let it cool down a bit, hopefully preventing the fuel from evaporating in the fuel lines from the heat radiating off the engine.

Tune your carb. This could be the reason for hard starting in general. In addition, most chainsaw millers I know tend to run a hair on the rich side. This can help the saw run a little cooler (but you don't want to go too far on this).

Consider a muffler mod. Letting the saw breathe easier can help it run cooler. I'm not all that familiar with how the Stihl 660 does with this, so I'll defer to those more knowledgeable than I on the subject on whether it's something to do in your case.
Title: Re: Hard starting chainsaw
Post by: massmanute on October 19, 2018, 07:35:25 PM

Good ideas. Thanks.