Free-spinning chain while idling

A

Avery

Location
Coastal Maine
Hi guys,

Apologies up front if this has been addressed, but I did use the 'search' function with multiple keywords and read all five pages of this forum before posting (couldn't find my answer, obviously.)

I just put a bigger bar on my Jonsered 490 (20", up from a 16".) The saw handles the longer bar ok, although I can bog it down if I try, but after getting the saw back from the shop (general tuneup and bar installation) the chain freewheels when the saw is idling. I actually took a nip out of my chaps last week while I cleared a branch (saw was dangling from the rear grip in my left hand) due to the chain's spinning.

Over the course of two hours' cutting, I noticed that it seemed to get faster and faster, too. Could this be due to the new chain wearing in? The chain tension seems alright...I'm thinking there must be an adjustment I can make to stop this dangerous condition. Would it be to the clutch?

Any info on what to tweak would be appreciated.

Thanks.
 
It is one of two things.

The Idle screwon te carb is turned in too far...most likey this one.

OR

The clutch springs are starting to go causing the shoes to keep in contact with the clutch.
 
Re: Your Answers

A grabby clutch doesn't have to have the saw running to make the chain turn around the bar, just trying to start a saw with weak springs will make the chain turn.

Larry
 
Re: Your Answers

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Since it was just "tuned" by the "shop" I would bet its the idle screw's setting.

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I agree with this general logic but it could also be that your lo speed screw is set too lean, this of course does tie in with the idle speed screw being mis-adjusted. Might also explain the bogging with the 20" bar as roughly 30% of your hi speed mixture comes from the lo speed fuel circuit.
 
Re: Your Answers

Bevis,

I posted a reply a couple of days ago but tonight I see that it didn't go up; I must have fat-fingered something.

Thanks for your diagnosis. I'm overseas until the 3rd of January but will break out the manual when I get home and try to figure out what to tweak to stop the chain from free-spinning and also to try to regain my top-end power.

I'll let you know what ultimately works.

Best to all for the New Year,

Avery
 
Re: Your Answers

[ QUOTE ]
Best to all for the New Year,

Avery

[/ QUOTE ]
Same to you Avery! Have a safe trip home.

Good luck with your saw.
 
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