Jonsered 525 - Stuck Chain Brake?

[jazzman]

I have been given an old Jonsered 525 chainsaw, which I now have managed to get running again. However, there appears to be a problem with the chain brake and appears to be stuck on. I have taken the brake cover off and the default position is with the brake on.

 

Checking online this brake cover seems to be different from the standard chainsaws and there is no option to release a stuck brake. Anyone with experience with Jonsered chainsaws and can offer advice on how to release the brake?

 

Thanks

[pleasant]

In your video that brake band is in the disengaged position- there is nowhere around the circumfrence for it to expand any further if it wasn't already disengaged. The motion of the lever against the band looks to have been re-assembled at some stage incorrectly as it is working in the opposite direction to pull the band in to activate the brake

Edited September 30, 2022 by pleasant

[pleasant]

Take a look at this video at about the 6min 30sec mark and you will see when the chainbrake is removed it is deactiaved and the band is in the same position as yours.

 

 

[jazzman]

Thanks for the video, that is one dirty cover so it's a job to see what's going on.

 

Not being a chainsaw expert perhaps I am giving the wrong information? The default position on the handle is when the band is at it's smallest, when the handle is pulled the band opens up (which I presumed is the brake is then off) when the handle is released it springs back into the compressed band position.

 

I thought that the chain brake should release and stay released once the brake handle is operated and becomes engaged again if there is a kick back?

 

Any idea if these covers are serviceable, doubt if new ones are available nowadays.

[pleasant]

They are serviceable. Parts scarce though. Default position should be disengaged/off/band expanded to its largest.

 

There should be little or no friction between the drum and the band in normal operation, so if you are suggesting it is trying to compress all the time, then like i say, it has developed a fault through part of the mechanism failing or has been re-assembled previously incorrectly. Google for a pdf parts list and take a look it will give you an idea of how it goes together and how to get it apart.

Edited September 30, 2022 by pleasant

[Stubby]

1 hour ago, jazzman said:

 

 when the handle is pulled the band opens up (which I presumed is the brake is then off) when the handle is released it springs back into the compressed band position.

 

 

This is the bit that is frack to bunt .  Normally you push ( with the back of your wrist ) the handle away from the saw body ( toward the bar ) and this engages the brake . You then pull it back toward you to disengage the brake . As said something is worn/assembled wrong . 

[adw]

3 hours ago, jazzman said:

I have been given an old Jonsered 525 chainsaw, which I now have managed to get running again. However, there appears to be a problem with the chain brake and appears to be stuck on. I have taken the brake cover off and the default position is with the brake on.

 

Checking online this brake cover seems to be different from the standard chainsaws and there is no option to release a stuck brake. Anyone with experience with Jonsered chainsaws and can offer advice on how to release the brake?

 

Thanks

The brake is loaded, so the hand guard will fall back to the neutral position, all you are doing that i can see is pulling the hand guard back to the loading position again, lets see a video of you pushing the hand guard forward to engage the brake.

[pleasant]

52 minutes ago, adw said:

The brake is loaded, so the hand guard will fall back to the neutral position, all you are doing that i can see is pulling the hand guard back to the loading position again, lets see a video of you pushing the hand guard forward to engage the brake.

I agree......it just looks like the band is disengaged already, so just pulling the lever back further is just as far as it will go against the 'stop' as the band cannot expand any further due to the confines of the cover mounts. Like you say- push it hard forward and the band should compress like it is designed to. I don't quite understand what the issue is here. The brake is disengaged and the band is fully expanded as it should be.

[Stubby]

Yep I think you are not pushing it forward hard enough . There should be some initial resistance and then an audible " click " and the band will snap on . Probably needs to be on the saw to do it unless you can clamp the whole assembly to the bench  with a G clamp or similar .

[jazzman]

Update: Reassembled the brake cover, and it was because of inefficient pressure being applied to the brake handle, still seems to be on the stiff side?

When the brake is in the disengaged mode (brake off) the chain will not fully rotate on the bar, is this how it should be?