Clutch Removal - Near Miss

[Philbert]

There are a lot of clutch removal threads here on AS - I would have posted this experience in one of them if I could have found a 'main' one. Most of the threads describe three ways to stop the piston for clutch removal:
- commercial piston stop;
- rope stuffed through the spark plug hole;
- use of an air-impact wrench.

I am cleaning up an older, STIHL 024AV Super, that is in really nice shape, so I decided to 'do it right' and use the STIHL OEM/factory piston stop. The muffler was still on, and I guess that I did not get the end far enough into the exhaust port (or maybe the end was too large to fit?). The piston stop slipped and the clutch did not move, so I used the rope trick and got it off.

But something did not feel right, and the piston stop looked a little rough at one end, so I pulled the muller and found what is shown in the photo below inside the muffler. Feel better now that I got what looks to be all of the 'extra' parts out, but I feel a whole less confident in the OEM piston stop right now!

Philbert

 

[young]

...... I guess that I did not get the end far enough into the exhaust port (or maybe the end was too large to fit?)......

this stihl piston stop is design to wedge itself between the top of the cylinder and piston, not exhaust port.

 

[Philbert]

this still piston stop is design to wedge itself between the top of the cylinder and piston, not exhaust port.

Well THAT would explain the problem! The angle of the tool appeared to match that between the ports, and the size and shape of the end appeared to match the exhaust port (see what happens when some of us get things without instructions?).

Thanks for setting me straight, and for restoring my faith in OEM tools! Hopefully, my story and your advice will be helpful for others as well. Rep sent.

Philbert

 

[young]

Well THAT would explain the problem! The angle of the tool appeared to match that between the ports, and the size and shape of the end appeared to match the exhaust port (see what happens when some of us get things without instructions?).

Thanks for setting me straight, and for restoring my faith in OEM tools! Hopefully, my story and your advice will be helpful for others as well. Rep sent.

Philbert

btw that piston stop is still good. :msp_biggrin:

 

[zogger]

Kinda sorta looks like you could heat up an old toothbrush and bend the handle like that....

With that said, I find the rope trick works fine.

Glad you didn't bust anything important! Tell ya what I don't like, those kind that screw into the sparkplug hole. They look like a disaster waiting to happen.

 

[promac850]

Kinda sorta looks like you could heat up an old toothbrush and bend the handle like that....

With that said, I find the rope trick works fine.

Glad you didn't bust anything important! Tell ya what I don't like, those kind that screw into the sparkplug hole. They look like a disaster waiting to happen.

Those are a disaster waiting to happen... seen and heard lots about guys punching a hole into the top of the piston with a piston stop of that type. Bad idea, worse IMO than using an impact... the rope trick is okay, but make damn sure that the end(s) of the rope don't get into the exhaust port, and make sure the piston is near TDC or you can bend the connecting rod.


What I do for clutch removal on a saw that has a one piece crank (one piece pressed and then welded, or one piece cast or forged crank) is simply hold onto the flywheel while loosening the clutch nut.

For one that is of the pressed three piece crank designs (like the Husky 350 I used to have) is pull the cylinder and put a screwdriver in between the PTO crank weight and the case, and then loosen the clutch nut.

If it's a three piece in an enclosed (PITA to disassemble/assemble) case, then I'd probably use a small low power impact on it, (no IR 2135's here...) and use something to hold the clutch if it's held on by a nut. If the clutch itself is threaded on, I'd probably go the full ten yards and tear the thing down so I can wedge something between the PTO crank weight and the case... last thing I want to do is break something. I'm too hard on myself when I break/damage stuff. I never let myself live it down.

 

[spacemule]

Those are a disaster waiting to happen... seen and heard lots about guys punching a hole into the top of the piston with a piston stop of that type. Bad idea, worse IMO than using an impact... the rope trick is okay, but make damn sure that the end(s) of the rope don't get into the exhaust port, and make sure the piston is near TDC or you can bend the connecting rod.

The closer the piston is to TDC, the more force the connecting rod will have to absorb.

 

[lone wolf]

3/8 air gun with the spark plug in the compression will hold the motor just enough to get it off of there.Do not use a 1/2 air gun and do not turn it counter clockwise.

 

[promac850]

The closer the piston is to TDC, the more force the connecting rod will have to absorb.

I'm trying to remember if that's the case or not...

I may be wrong.

 

[Stihl310]

Maybe I'm way off here, but I've found the easiest way to stop the piston was to have a piece of nylon cut to length equal to the dia of the cylinder. I then just pop the cover off the muffler and insert it through the exhaust port. No question as to whether it's in correct or not, cause you can see it.

To get it out I just lower the cylinder and take long nose needle nose and pull it back out. I cut the nylon about 1/16 less the width of the exhaust port. Seemed to work, and no question as to whether it was in or not. Am I wrong to do it this way??

 

[zogger]

Maybe I'm way off here, but I've found the easiest way to stop the piston was to have a piece of nylon cut to length equal to the dia of the cylinder. I then just pop the cover off the muffler and insert it through the exhaust port. No question as to whether it's in correct or not, cause you can see it.

To get it out I just lower the cylinder and take long nose needle nose and pull it back out. I cut the nylon about 1/16 less the width of the exhaust port. Seemed to work, and no question as to whether it was in or not. Am I wrong to do it this way??

You cut a piece of nylon what?

 

[Stihl310]

Cut a piece of nylon slightly less than the dia and slightly less than width of exhaust port. Place it on top of cylinder and rotated crank up to make contact. Then pull the clutch. When done you reverse crank and lower. Pull the nylon back out...

 

[Stihl310]

I have heard of the rope trick and just didn't feel comfy stuffing rope in and hoping I didn't get it in the exhaust..

 

[RES]

Maybe I'm way off here, but I've found the easiest way to stop the piston was to have a piece of nylon cut to length equal to the dia of the cylinder. I then just pop the cover off the muffler and insert it through the exhaust port. No question as to whether it's in correct or not, cause you can see it.

To get it out I just lower the cylinder and take long nose needle nose and pull it back out. I cut the nylon about 1/16 less the width of the exhaust port. Seemed to work, and no question as to whether it was in or not. Am I wrong to do it this way??

So what you are saying is that you cut a chunk of nylon plate that is about 1/4" thick that can slide into the exhaust port, being slightly less than the width of the exhaust port. The length of the piece is such that it smaller than the diameter of the piston. You then rotate the crank so that the piston carries the nylon piece up against the top of the combustion chamber. Since the piston can not reach top dead center, it will allow you to loosen the nut. Sounds like a clever way of stopping the piston. Since the nylon piece is parallel to the wrist pin, it contacts the piston at the right places. The only negative that I can see is that the piston may be close to top dead center with this method.

 

[Fish]

You guys that discuss the "right" way to do it, keep me in the part selling business....

I have dismembered hundreds of saws in the last 4 years, not "1" problem yet....

 

[promac850]

You guys that discuss the "right" way to do it, keep me in the part selling business....

I have dismembered hundreds of saws in the last 4 years, not "1" problem yet....

Well, edumacate us already... please.

 

[RiverRat2]

friendly advice

Here is what Ive found that is fool proof and works every time,,, Without damaging the pistion,,, takes a little more time you can do it two ways,, the easiest way for me is a good/fresh piece of 4mm starter cord,,, if the piston is still good and you plan to reuse it,, looking through the spark plug hole,, bring the piston up toward tdc to were you can easily be sure you are well above the top of the exh. port,,, with the smaller 4mm startercord doubled,,, began pushing the cord in until you have a good bit stuffed in the comb. chamber ease the crank toward TDC and you will see it stops the piston pretty quickly and solidly

the second way is the same just pulling the muffler so you can see you are past/above the EX pt w/the piston crown

never use an impact,,, a good stihl Scrench works perfectly for the clutch or the flywheel

 

[Stihl310]

So what you are saying is that you cut a chunk of nylon plate that is about 1/4" thick that can slide into the exhaust port, being slightly less than the width of the exhaust port. The length of the piece is such that it smaller than the diameter of the piston. You then rotate the crank so that the piston carries the nylon piece up against the top of the combustion chamber. Since the piston can not reach top dead center, it will allow you to loosen the nut. Sounds like a clever way of stopping the piston. Since the nylon piece is parallel to the wrist pin, it contacts the piston at the right places. The only negative that I can see is that the piston may be close to top dead center with this method.

Yep. I can't see it being any more dangerous than using starter rope.

 

[Fish]

No, I just make money on all of the bad advice here..... So I don't talk bout it much....

 

[Philbert]

First, thanks again for the feedback, and for not making me feel like a total dork for mis-using the tool.

Maybe I'm way off here, but I've found the easiest way to stop the piston was to have a piece of nylon cut to length equal to the dia of the cylinder.

You cut a piece of nylon what?

So what you are saying is that you cut a chunk of nylon plate that is about 1/4" thick . . .

Yep. I can't see it being any more dangerous than using starter rope.

STIHL310 - are you using a piece of nylon rope, or nylon plate/plastic stock?

You guys that discuss the "right" way to do it, keep me in the part selling business.... I have dismembered hundreds of saws in the last 4 years, not "1" problem yet....

We sit at your feet, eager to learn Professor Fish. Are most of those new saws, old saws, etc.?

I don't own an impact wrench, and certainly don't have one in the field. It is nice to be able to use a spoon or rope if you need to pull one (e.g. replace a sprocket on a Husky).

Philbert