Stihl BR550. This a first

[Hammermechanicman]

Fan was so tight on the crankshaft that the piston stop put a hole in the top of the piston. Took a 2ft long breaker bar and a lot of a$$ to break it loose.

 

[ILENGINE]

I have been coming across a lot of chainsaws lately that they are installing the clutches with red loctite and need to use a small torch to warm the clutch in order to break them lose from the crankshafts. So is it possible they used loctite on the fan threads.

 

[StarTech]

These fans naturally tighten over an long period of use.

From the service manual...

Right-hand thread. Very high
release torques may be necessary
after long periods of operation.

Should just use an impact to spin off the fan after you remove the recoil but leave the spark plug in for compression loading. Using a breaker bar and piston stop is just asking for a hole in the piston. I nearly did the same here several years ago but I tried the impact which like charm.

When installing the fan use no lube and torque to 22 ft/lbs (264 in/lbs). Now this where you will the piston stop. Even then 22 ft/lbs is a lot to bear by the piston.

 

[Hammermechanicman]

I tried the impact on the fan nut once. Broke the nut out of the plastic fan. Proline AM piston only $38 so not a disaster

 

[StarTech]

Maybe I have a lighter touch or maybe I just got lucky

 

[bertsmobile1]

Same problem here
I warm the fan nut
Apply penetrant allow to cool heat it up again spray penetrant allow it to cool , repeat many times
Try rattle gun if no joy back to the heating cycle .
Local Stihl shop says they cut the fans off & charge customer for new fan
And yes they really do self tighten a massive amount .

 

[StarTech]

Boy did I have my screwed on wrong on this one after a few restless nights I went to my hand written notes. Hammer your are right about using a pull bar the remove. My notes suggest the fan wheel takes too much inertial to get started with the impact and a pull bar is the way to go.

Boy do I feel like an idiot right now but I admit I was wrong on this one. I reckon I can blame it on old age.

 

[Hammermechanicman]

Boy did I have my screwed on wrong on this one after a few restless nights I went to my hand written notes. Hammer your are right about using a pull bar the remove. My notes suggest the fan wheel takes too much inertial to get started with the impact and a pull bar is the way to go.

Boy do I feel like an idiot right now but I admit I was wrong on this one. I reckon I can blame it on old age.

Haha. I've never made a mistake. Well, at least not in the last 5 minutes. I had the blower engine completely apart 6 times trying to figure out why it had low compression. Not until I really cleaned the carbon off the top of the piston did I realize it had a hole in it. The blower would almost start with the hole in the piston.

 

[Fish]

The impact doesn't do much, I had to buy the Stihl piston stop and use a wrench/bar.
Otherwise I use the impact.

 

[Scrubcadet10]

I don;t like using piston stops as to me they can put too much pressure on one small area. I keep a clean length of paracord to use as a piston stop.
MY PISTON STOP IS BETTER THAN YOUR PISTON STOP