Chain spins at idle when low on gas

[Amin_1992]

Hey guys. Never saw this phenomenon before!

I was running my MS261 bucking wood, when I noticed that after cutting a lot, idling, the chain was still spinning at a good speed! Never did that before. I grabbed my kit and was beginning to adjust her, when she died. I then realized I was out of fuel ha.

Anyway, refueled, and now the idle was back to normal. No chain spin at idle.

Curious if that is "normal" when low on fuel? My only thought was is that I was running extra lean since the gas was about out, and that caused the inbalance in fuel/air, running lean and increasing idle speed a bit.

What do you think? Ever see that before?

 

[Marley5]

The increase in idle is how I know my saw is about to run out of fuel.

 

[Amin_1992]

The increase in idle is how I know my saw is about to run out of fuel.

Ha! In 7 years of using a chainsaw steadily I never noticed that little trick. Thanks!

 

[lone wolf]

Hey guys. Never saw this phenomenon before!

I was running my MS261 bucking wood, when I noticed that after cutting a lot, idling, the chain was still spinning at a good speed! Never did that before. I grabbed my kit and was beginning to adjust her, when she died. I then realized I was out of fuel ha.

Anyway, refueled, and now the idle was back to normal. No chain spin at idle.

Curious if that is "normal" when low on fuel? My only thought was is that I was running extra lean since the gas was about out, and that caused the inbalance in fuel/air, running lean and increasing idle speed a bit.

What do you think? Ever see that before?

Can you check the idle speed with a tach?
Also look and see if one of the clutch springs are broken.

 

[Amin_1992]

Can you check the idle speed with a tach?
Also look and see if one of the clutch springs are broken.

I could yes but I could audbily hear it was running faster with an empty tank, then returned to a normal sound after refueling.

 

[Woodtroll]

My only thought was is that I was running extra lean since the gas was about out, and that caused the inbalance in fuel/air, running lean and increasing idle speed a bit.

Yes, I think you're exactly right. I try to cut my saws off as soon as they do this, to save them from running completely dry. That way I don't have to add extra pulls to prime it again after refueling. I'm lazy that way.

 

[Old2stroke]

Normal. As a saw runs out of fuel, it starts to run lean and that’s what makes it speed up