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Stihl FS45 string trimmer bump knob - cannot remove

#1

D

dukerocks

I have a Stihl FS 45 string trimmer with a bump knob I cannot remove. I have used opposing pipe wrenches and it will not twist off. What has happened and better yet what do I have to do to get it off?


#2

Fish

Fish

You are turning the knob to the left? Right?


#3

Fish

Fish

Errrr. Correct?


#4

D

dukerocks

To the left, counterclockwise when you look at it. I have been refilling line for years. I'm not a newby, I'm 75 years old. Do we have any better suggestions? Thanks., Bob


#5

Fish

Fish

Yeah!!! Turn it to the left!!!!

If not possible, then you will have to cut off the plastic around the nut, which is housed in the knob.


#6

Fish

Fish

Sucks, don't it?????


#7

Fish

Fish

The cap has the plastic knob, a big nut inside, and a snap ring that keeps it inside...

If it won't unscrew, then you re screwed...... And have to put up with the silly comments of those that work on said,"KNOBS".........
Sux, don't it?????


#8

D

dukerocks

I did get the plastic cut away from the nut on the bump knob. I am using a penitrating oil to soak around the nut over nite. My additional problem is when I tried the opposing pipe wrenches, I head something snap, and believe it is where the drive cable connects to the motor. I'll have to take the motor housing off to check that out because when I turn the nut, the cable just wants to spin freely. Maybe there is a broken wooddruff key, set screw in there???? I have got to stop the drive cable from spinning to unwrench the nut. Any suggestions? Bob


#9

Fish

Fish

No, that flex cable was up there, and no matter what you try you will get anywhere up at the engine side.


#10

Fish

Fish

Once you have it down to the nut, take it by a shop and let them tap it with an impact wrench.


#11

D

dukerocks

I'd like to keep that flex cable from turning when I try to twist off the nut. The only place I can reach the other end of the flex cable is at the motor drive shaft.


#12

Carscw

Carscw

dukerocks said:
I'd like to keep that flex cable from turning when I try to twist off the nut. The only place I can reach the other end of the flex cable is at the motor drive shaft.
Click to expand...

You are not going to remove the nut by holding the flex cable. You will just twist the cable and will need to replace it.


#13

D

dukerocks

So, do you or anybody have a practical solution for removing the nut?


#14

Carscw

Carscw

Not all nuts are left handed.
I have some trimmers that the nut comes off going counterclockwise and others that come off going clockwise.

Did you try both ways ?
If the head turns counterclockwise when trimming then the nut comes off clockwise.


#15

EngineMan

EngineMan

Should there not be a hole in the deflector for a locking pin to go into...!


#16

D

dukerocks

WOW, that makes a lot of sense, I'm hoping you are right about that pin. I did hear something snap when I was using opposing pipe wrenches. I will check that out. Is there a parts diagram maybe showing that pin? Thanks


#17

Fish

Fish

No, no pin on the curved shaft


#18

Fish

Fish

Take that back, there is a hole for a lock pin!


#19

Fish

Fish

Not a lot of plastic/meat there, but it may hold.

DSCN6215.jpg

DSCN6216.jpg


#20

D

dukerocks

Please, somebody correct me if I'm wrong. It seems I should cut off the entire black plastic cutting head to get to the bottom side of the nut?


#21

Fish

Fish

I'll take some better pics here in a minute....


#22

Fish

Fish

This is what the cutting head sits on.DSCN6217.jpg


#23

Fish

Fish

This is the mating side view of the cutting head, it has the nut shaped hole to fit on the shaft end.DSCN6216.jpg


#24

Fish

Fish

Now, they put this hole here so you might put a pin or nail in to hold the head while you try to loosen the nut.

DSCN6215.jpg


#25

Fish

Fish

And inside the plastic nut is just a regular Stihl bar nut.


DSCN6218.jpg


#26

D

dukerocks

Thanks for the EXCELLEXT pics. I used a ice pick through that hole but it would not engage into any hole in the backside of the cutting head - I spun the cutting head slowly while pushing on the icepick. Even if I prevent the cutting head from turning this will not keep the flex cable from turning while I try to turn the nut. I have got to prevent the flex cable from turning while trying to twist off the nut. Thanks


#27

Fish

Fish

It sounds like the black plastic cutting head has rounded out, the hex headed hole should lock on the end of the shaft and it should turn only when the shaft turns.


#28

D

dukerocks

It did not round out - I do have the bare exposed nut. It does not have any plastic around it - the bump knob has been completely cut offf. I need to keep the flex drive cable from turning!!!! Bob


#29

D

dukerocks

I am attaching pics of what I am working on, just to show you where I am at with this project. As I say, I completely have the bump knob cut away showing the bare nut.

Attachments









#30

Fish

Fish

If you literally clamped the whole black cutting head in a big vise so it couldn't move at all, and turned the nut to the left, what would happen?

Would the drive cable still turn?


#31

Fish

Fish

This is pretty much what you have now, correct?

DSCN6220.jpg


#32

Fish

Fish

now, if you were to lock the black plastic bumphead in vise, and turn the nut to the left it should unscrew right off. If the shaft is turning in the tube,
then the bump head is stripped out. Because the two mating sides of that look like this:

DSCN6221.jpg

DSCN6222.jpg


#33

Fish

Fish

You could remove the tube from the engine and try to clamp on the drive cable, but you would just destroy that too.

You could just get a good looking female relative to bring it by a Stihl dealer, and they would just zip that little nut right off with an impact wrench, if it isn't too boogered up, and sell you a new head, and you could be trimming tonight, and they probably wouldn't charge you any labor.


#34

Fish

Fish

What part of Indiana are you in?


#35

Carscw

Carscw

Place a small flat-head screwdriver through the holes in the plastic deflector and the thrust plate below it. This locks the shaft in position to remove the spool head.

Turn the nut counterclockwise.


#36

D

dukerocks

Yes, exactly! This is what I have been trying to tell you. If the other end of the drive cable was attached to the motor end it would make the piston move. This is not happening!! This nut will just spin in either direction, left or right just by holding the cutting head!! Actually, you don't even need to hold the cutting head!!!


#37

Carscw

Carscw

dukerocks said:
Yes, exactly! This is what I have been trying to tell you. If the other end of the drive cable was attached to the motor end it would make the piston move. This is not happening!! This nut will just spin in either direction, left or right just by holding the cutting head!! Actually, you don't even need to hold the cutting head!!!
Click to expand...

Turning the cable will not turn the engine. Why you ask?

Because the cable goes to a clutch.
Same type clutch that you would find on a go cart.


#38

Fish

Fish

No, there is a centrifugal clutch on the other end, the drive cable only locks to the engine when the engine rpms reach a certain level.

But either way, if you can hold the black plastic trimmer head in your hand, and turn the nut to the left, then you have a problem in the trimmer head.

Cheaper weedeaters did not have a clutch, and their cable was directly attached to the engine.


#39

EngineMan

EngineMan

I am not sure if you have this....

Attachments


  • FS-45-46-Weed-Trimmer-Instruction-Manual.pdf
    1.8 MB · Views: 32


#40

D

dukerocks

Fish said:
now, if you were to lock the black plastic bumphead in vise, and turn the nut to the left it should unscrew right off. If the shaft is turning in the tube,
then the bump head is stripped out. Because the two mating sides of that look like this:

View attachment 21656

View attachment 21657
Click to expand...

That's exactly what I have. But in the one pic the cutting head is removed and mine is not. Bob


#41

D

dukerocks

EngineMan said:
I am not sure if you have this....
Click to expand...

Thanks for the manual. There are some great illustrations. Bob


#42

D

dukerocks

Fish said:
This is pretty much what you have now, correct?

View attachment 21655
Click to expand...

Exactly, Bob


#43

D

dukerocks

Fish said:
What part of Indiana are you in?
Click to expand...

Fishers, IN just adjacent to Indpls in the NE corner of Indy.


#44

D

dukerocks

Fish said:
This is pretty much what you have now, correct?

View attachment 21655
Click to expand...

That's where I am at.


#45

D

dukerocks

Fish said:
You could remove the tube from the engine and try to clamp on the drive cable, but you would just destroy that too.

You could just get a good looking female relative to bring it by a Stihl dealer, and they would just zip that little nut right off with an impact wrench, if it isn't too boogered up, and sell you a new head, and you could be trimming tonight, and they probably wouldn't charge you any labor.
Click to expand...

Good thought! I should try it if all else fails. But feel the cable will turn with their air tool too. Bob


#46

D

dukerocks

Fish said:
This is what the cutting head sits on.View attachment 21615
Click to expand...

Wish I could get to this point! Bob


#47

D

dukerocks

Fish said:
This is pretty much what you have now, correct?

View attachment 21655
Click to expand...

Exactly, Bob


#48

Fish

Fish

An impact would zip it off easily, which is why I suggest you do this. An air wrench, and an impact wrench, they are 2 totally different tools, drop by a Stihl dealer this morning, they probably wouldn't even charge you to try it.........


#49

D

dukerocks

Fish said:
An impact would zip it off easily, which is why I suggest you do this. An air wrench, and an impact wrench, they are 2 totally different tools, drop by a Stihl dealer this morning, they probably wouldn't even charge you to try it.........
Click to expand...

The good new this morning is that I got that nut off. I had soaked it in penitrating oil for a couple of days and created my own impact tool with a socket & wrench. I put the sock on the nut with the wrench attached and smacked the hell out of the wrench with a large hammer a couple of times and it broke loose. Now I have to wonder what did I hear snap when I used the opposing wrenches. Any ideas, or just try to start up to see if anything turns? Of course, I need a new knob, as I had cut away the old to get to the nut. Thanks


#50

D

dukerocks

Fish said:
now, if you were to lock the black plastic bumphead in vise, and turn the nut to the left it should unscrew right off. If the shaft is turning in the tube,
then the bump head is stripped out. Because the two mating sides of that look like this:

View attachment 21656

View attachment 21657
Click to expand...

Now that I have my trim head out, I see a spring in mine that you don't have in the lst pic. However, I don't know if this spring is long enough, maybe part broken off (snap I heard). I don't see any broken part of it though.


#51

Fish

Fish

You mean the spring that is supposed to be inside?

DSCN6224.jpg

Show a pic of the back side and inside of your black cutting head.


#52

D

dukerocks

Fish said:
An impact would zip it off easily, which is why I suggest you do this. An air wrench, and an impact wrench, they are 2 totally different tools, drop by a Stihl dealer this morning, they probably wouldn't even charge you to try it.........
Click to expand...

Got it all put back together, started it up, works fine, just need to get a new bump knob. Thanks for everyones input. Bob


#53

Fish

Fish

Works fine without the bump knob?


#54

Fish

Fish

Fish said:
Once you have it down to the nut, take it by a shop and let them tap it with an impact wrench.
Click to expand...

Wow, this was post #10.....


#55

D

dukerocks

Fish said:
Works fine without the bump knob?
Click to expand...

Well NO, not quite, needs the NEW bump head to work perfect. I fueled it up, started the engine, everything is good. Again, thanks for all the help to everyone. Bob


#56

G

gaalford

I know this string is old but Im posting for anyone else that has this problem. My fs 45 is doing the exact same thing. Take a screw driver and pry the bump button off. take a grinder with a metal cutting blade or a hacksaw and cut a slot into the shaft. This will allow you to hold the shaft in place while turning the nut with a 3/4" inch wrench. For some reason the button seems to be clamping itself on the shaft of the housing and preventing it from turning. It's as if the bump button needs a spacer to prevent it from bottoming out. Even if you put it on loosely the button will tighten itself onto the shaft. I think it is going below the threads and that's why it doesn't twist back off. I bought a head from a tractor supplier that carried stihl products and it was supposed to be an exact fit. I'm going to cut a spacer from a plumbing tail piece tomorrow. Hopefully, this will work.


#57

J

Jamesck

gaalford said:
I know this string is old but Im posting for anyone else that has this problem. My fs 45 is doing the exact same thing. Take a screw driver and pry the bump button off. take a grinder with a metal cutting blade or a hacksaw and cut a slot into the shaft. This will allow you to hold the shaft in place while turning the nut with a 3/4" inch wrench. For some reason the button seems to be clamping itself on the shaft of the housing and preventing it from turning. It's as if the bump button needs a spacer to prevent it from bottoming out. Even if you put it on loosely the button will tighten itself onto the shaft. I think it is going below the threads and that's why it doesn't twist back off. I bought a head from a tractor supplier that carried stihl products and it was supposed to be an exact fit. I'm going to cut a spacer from a plumbing tail piece tomorrow. Hopefully, this will work.
Click to expand...

Thanks! I read for an hour before I saw your post and now I am finished!


#58

D

dukerocks

Jamesck said:
Thanks! I read for an hour before I saw your post and now I am finished!
Click to expand...

Thanks, this has been SOLD.

Thanks


#59

B

boydmiles

I know this is an old thread but it did tell me how to get the trimmer head off. I used the pry off the button method. Now why are they rounding out? Any way to prevent it from happening again?


#60

D

dukerocks

Hi, do not have this machine any longer.

Thanks


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