Chainbrake gets harder to use when saw is hot

[Les Cork]

Hi

This is on behalf of a mate who has a problem with chainbrakes getting harder to work when hot on his MS260 and MS440, has anyone else come across this ? Once cooled down they are fine.

This cutter has many other saws, 3 other 026's without the problem and is baffled why this happens.

 

Your help and how you solved the problem would be appreciated as the bruises on the back of his wrist will disappear.

[raker]

The answer could be in the question:`when hot`.If the clutch springs are needing replacing then the shoes will always be engaged with the drum.This will generate some heat.

Is the drum `blued`and hot to the touch?Is the chain still moving when idling. Brake on or off?

Heat expansion in this area will affect brake operation as the drum will expand and jam the brake band.

How well cared for are the saws? Gunked up around the band? Clutch bearing shot?

 

Just a few pointers mate.

Edited October 31, 2010 by raker

[skyhuck]

The chain brake handle can become soft and flexible when the saw exhaust gets hot, this can make applying the brake more difficult as you need to move it further before it comes on.

 

Check the silver foil is in place above the exhaust, as this helps deflect heat.

[Badgermert]

We have the same problems on some of our ms260's. Thought it might be be the rubber sleeve on the brake spring working its way towards the rear/back handle of the saw to start with, repositioned and seemed ok for a while then same old problem. Was it the chain brake handle worn, replaced it, no long term difference. Tried smoothing the slight ridged wear on the casing behind the chainbrake spring but still no difference.

[Stephen Blair]

has he cleaned the saw properly, guard off, drum off? Has he replaced the drum, spring and brake if they were worn. Does he cut with the saw blunt creating a lot of heat? Does he use this saw for ringing up/firewood where it would get a lot of constant use?

[Les Cork]

Thanks for your input, i didn't want to mention that the saws are maintained to a high standard, the bar and chains always sharp and checked frequently and the usage a complete mix of everything, my mate is an NPTC instructor, assessor and pro user of some 35 yrs and like badgermert has replaced everything trying to solve the problem. He has many saws the same which don't give any problems.

I will forward the comments so he can check the foil, clutch springs and bearing, it's interesting that others have experienced the same.

Between us we can find the answer and publish it for others to gain from if they suffer the same.

Any more ideas keep em coming

[Stephen Blair]

maybe just a bad plastic handle, it could of been in a batch made on a friday afternoon or monday morning, Mr Plastic mixer might of had a bad hangover and messed up his mix or summit:confused1:

[Swooop]

maybe just a bad plastic handle, it could of been in a batch made on a friday afternoon or monday morning, Mr Plastic mixer might of had a bad hangover and messed up his mix or summit:confused1:

 

We have a 660 at work, well maintained, that has the problem described.

Systematically replaced every part of the chain brake practical, inc handle, no joy.

Friday afternoon saw...

Runs fine though!

[scbk]

Probably a bit off topic, but I have a ms250 (don't mock me!) where the brake band snapped, then a few days after fitting a new one, the brake was getting harder and harder to engage and disengage. On close inspection the handle had a small crack opening up in it.

 

The new handle I bought (genunine stihl, same part no.) is more beefed up, and feels like it is possibly made of a different plastic, suggesting they know of a problem with handles breaking?

[18 stoner]

Quite common on 660's