Chainsaw Won't Start With Brake On

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SteveHGraham
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Chainsaw Won't Start With Brake On

Post by SteveHGraham » Thu Jan 03, 2019 6:39 pm

Here's a new challenge for everyone.

I have a chainsaw that won't start when the chain brake is on. The brake locks it up completely. It's a new problem. I put a new carb in the saw, and I was yanking the cord over and over trying to get it to start, and it started locking up.

I can probably get the saw to start with the brake off, but it's not a brilliant idea.

I can pay someone $85 per hour to figure it out, but I assumed some genius on this board could help me.
Every hard-fried egg began life sunny-side up.

John Hasler
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Re: Chainsaw Won't Start With Brake On

Post by John Hasler » Thu Jan 03, 2019 7:16 pm

I've never had a chainsaw that would start with the brake on.

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SteveHGraham
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Re: Chainsaw Won't Start With Brake On

Post by SteveHGraham » Thu Jan 03, 2019 7:35 pm

You must have had really bad luck.
Every hard-fried egg began life sunny-side up.

John Hasler
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Re: Chainsaw Won't Start With Brake On

Post by John Hasler » Thu Jan 03, 2019 8:40 pm

I just don't own any power tools manufactured in this century.

spro
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Re: Chainsaw Won't Start With Brake On

Post by spro » Fri Jan 04, 2019 12:13 am

It may be oily wood chips have packed the centrifugal clutch. Pull starting, then, can't overcome the friction when the brake is on. These 2 cycles have to go a few rotations to fire right, without resistance.

mihit
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Re: Chainsaw Won't Start With Brake On

Post by mihit » Fri Jan 04, 2019 3:58 am

spro wrote:
Fri Jan 04, 2019 12:13 am
It may be oily wood chips have packed the centrifugal clutch. Pull starting, then, can't overcome the friction when the brake is on. These 2 cycles have to go a few rotations to fire right, without resistance.
This is closest to my guess. But if you let a saw get that filthy you don't deserve to have it.

My first guess is stretched throwout springs flying out at too-low revs and binding on the drum, acting as a drum brake.

I don't start saws with the chain brake on and can't see why you would need to.

Other guesses, sheared flywheel key or dropped pickup coil, seized bore.

Dismantle it for diagnosis, There's not much to them.

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SteveHGraham
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Re: Chainsaw Won't Start With Brake On

Post by SteveHGraham » Fri Jan 04, 2019 9:22 am

So maybe the clutch needs to be replaced, or at least the springs.

I can't get the clutch drum off to save my life, and I believe it's supposed to slip right off. I guess that means the clutch is grabbing the drum all the time.
Every hard-fried egg began life sunny-side up.

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mcostello
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Re: Chainsaw Won't Start With Brake On

Post by mcostello » Fri Jan 04, 2019 10:04 pm

It's not left hand thread is it, just sayin..............

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SteveHGraham
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Re: Chainsaw Won't Start With Brake On

Post by SteveHGraham » Sat Jan 05, 2019 9:41 am

I got it off by holding the sprocket with channel locks and beating the shaft end with a ball peen hammer. I still don't know what made it stick. I have a clutch removal tool on the way, and I'm going to remove the clutch and look behind it.
Every hard-fried egg began life sunny-side up.

mihit
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Re: Chainsaw Won't Start With Brake On

Post by mihit » Sun Jan 06, 2019 4:23 am

Saws do have the clutch throwout screwed on. The drum is either on needle roller or a bush -It should lift off once the circlip is removed.
For the throwout I will usually wedge a screwdriver across the flywheel fins (at the other end of the crank) (but any method to immobilise the crank will work- hydraulic lock the cylinder if you prefer) and nudge the throwout assy with a punch to loosen it. Re-assy with anti-seize!

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SteveHGraham
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Re: Chainsaw Won't Start With Brake On

Post by SteveHGraham » Fri Jan 11, 2019 5:10 pm

The saw parts arrived. I took the clutch off, hoping my missing screw was behind it, but there was nothing there.

I dry-fitted the clutch to the drum and found that the drum was distorted. This must be the cause of the problem.

I can't figure out what caused it to go out of round. The saw has never been dropped or otherwise struck. I am wondering if heat somehow warped it. I thought maybe I had revved the saw with the brake on; I know saws get hot when the chains don't move. I don't know of any reason why I would do that. Someone has pointed out to me that revving a saw with the brake on will make the clutch engage and heat up the drum. I don't see wear inside the drum or on the clutch, but the outside of the drum has a mark on one side where the brake strap bit into it.

When this mess started, I didn't know chainsaws had centrifugal clutches. I thought maybe there were elves in there. I have learned quite a bit about the way the saw works.

I reinstalled the drum with anti-seize while wondering why Echo didn't do the same thing.

I ordered a new drum, plus a needle bearing. The old bearing looks fine, but I don't want to install a new drum and then find out the bearing is bad. I don't know what to lube the bearing with.
Every hard-fried egg began life sunny-side up.

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mcostello
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Re: Chainsaw Won't Start With Brake On

Post by mcostello » Fri Jan 11, 2019 9:50 pm

I have always used wheel bearing grease.

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