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Chain saw engine instantly cuts off when applying chain brake

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Uncle Ben

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Getting my saw tuned up and prepped to cut wood for fall, and I'm having an issue with the chain brake. When the chain brake is applied, the pull cord is taut and will not pull, so the saw has to be started with the brake off. It starts and runs well now (after tuneup), but if I apply the chain brake while it's running, it will instantly kill the engine. I say "instantly" because it is not really like a "stall", it literally dies the moment that the chain brake is applied, no lag, no sputter...in an instant.

The brake will have to be disengaged to restart the saw, but it will start back up no problem, but the brake cannot be applied without killing the engine, so it can't be left at idle in order to sit the saw down for a moment, or to do anything between cuts.

I have never working on a chainsaw clutch before, so I'm not sure what could cause this or what to look for...or if I just need a new clutch.
Thanks!
 
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Beerhippie

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Your clutch is locked up. Not only is it irritating, it's downright dangerous--having the chain running on start-up is a bad thing.

Clutch is a simple centrifugal clutch. You don't mention what brand of saw--some are easy, some require a spline wrench.
 
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Kent_B

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My Stihl has a roller bearing between the clutch and crankshaft. I've had those bearings fail and seize. It's a good idea to periodically remove, clean and re-lube. I keep a spare in my chainsaw tool box.
 
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The Cobbler

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Uncle Ben

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It's a Poulan Pro PR4218 (18" bar). I'll open it up to see if I can spot anything broken or damaged, at least as a starting point.
 
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PCustoms

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Uncle Ben said:
It's a Poulan Pro PR4218 (18" bar). I'll open it up to see if I can spot anything broken or damaged, at least as a starting point.
Click to expand...

I suspect that parts/service will be very limited, but worth looking for an obvious issue
 
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Milton Shaw

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My electric chainsaw won't run with the brake on. Which means there is a switch on the chain brake that turns off the saw. My second saw with chain brake, gas ones will start, electric won't.
 
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Uncle Ben

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I opened up the clutch and took some photos to see if anyone could give me some insight. The metal ring around the outside of the clutch area was fully seated, but I pulled it up a bit to get a look at it, so that is why you see it raised on one side. The 3 sliding portions of the clutch (not sure what they are called) are loose and can be slid toward the center or towards the outside freely, so they have no tension. I’m assuming that the outer ring is supposed to be putting tension on these, but I’m not sure what it is supposed to look like or how it goes together.
 

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Uncle Ben

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Looks like maybe it's missing a spring?? Not sure how it could be missing since I've never taken this clutch apart before...
 
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PCustoms

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larry_g

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PCustoms said:
Where did you see a spring here?
Click to expand...
It's quite obvious if you open the picture of part #6 the clutch.

To the OP, I'd suggest that you replace the clutch and the clutch drum. Common wear/repair parts in a chain saw. Some suggest that the clutch drum be replaced when a new chain is installed.

lg
no neat sig line
 
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Uncle Ben

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Silly me, the broken spring was sitting inside the clutch drum. One end of the spring still has a loop on it, but the other end snapped off.
 

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Uncle Ben

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I’m not sure how it hooks back in there, but I’m wondering if the other end of the spring was just a hook that hooked into the loop of the other side of the spring, making the spring into a loop that holds the clutch toward the center.
 
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Beerhippie

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Uncle Ben said:
I’m not sure how it hooks back in there, but I’m wondering if the other end of the spring was just a hook that hooked into the loop of the other side of the spring, making the spring into a loop that holds the clutch toward the center.
Click to expand...
It's easy. The new clutch you are going to buy and install already has the spring installed.

Expecting a dead cat to catch mice....

I sure as hell wouldn't go as far as replacing the clutch drum every time I replace a chain--something I do more often than most because I do a lot of cutting stumps flush with the ground (or used to)--but replacing the clutch when it malfunctions is just good common sense.
 
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Uncle Ben

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I made a loop in the broken end of the spring and reattached it. I have a lot of cutting to do this weekend and a new clutch will not arrive by then, so I’m seeing if I can make do.
 

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larry_g

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Uncle Ben said:
I’m not sure how it hooks back in there, but I’m wondering if the other end of the spring was just a hook that hooked into the loop of the other side of the spring, making the spring into a loop that holds the clutch toward the center.
Click to expand...
With the new clutch costing less than $20 including the spring to me it is a no brainer to replace it all.

lg
no neat sig line
 
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Uncle Ben

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PCustoms said:
Yeah, that was added after the fact...
Click to expand...
You're correct, it was.

I also took apart the chain brake and blew everything out really well, and after putting everything back together the chain was still spinning fairly quickly at idle, so I adjusted the idle speed down and the chain stays still at idle now...and the brake is stopping the chain without slamming and instantly killing the engine now.

Thanks everyone for your input.
 
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