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Black & Decker String Trimmer Model ST4000 tap string advance doesn't work

#1

A

anthonyjaycorman

I've got one of these electric trimmers - motor works fine but the tap-to-advance stopped working ages ago. I can find no help online - there are similar discussions, but the photos show a mechanism that doesn't look like the inside of my trimmer (photos of the inside and the spool attached). It's not at all clear to me how it even works - in the other pics there's a spring armature, like a clock, that engages with a gear. Anyone ever fixed this problem for one of these?

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#2

A

Auto Doc's

I think your trimmer string is too thick of a diameter for this trimmer. There should be a spring in the middle that is not shown in your pictures.

Next option would be to replace this cutter head an install a universal it type.


#3

A

anthonyjaycorman

Auto Doc's said:
I think your trimmer string is too thick of a diameter for this trimmer. There should be a spring in the middle that is not shown in your pictures.

Next option would be to replace this cutter head an install a universal it type.
Click to expand...
I do have the spring, just didn't put it on for the photo. The string *is* thick*, but even with the standard thickness it wasn't advancing when I tapped. As far as I can tell, no parts are missing, based on this diagram:


It's not clear to me how the tap mechanism works - there's nothing visible when you remove the spool, so not clear how I might repair it.


#4

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Auto Doc's

Is part #11 in place under the string spool?


#5

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anthonyjaycorman

Auto Doc's said:
Is part #11 in place under the string spool?
Click to expand...
Yes


#6

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OldDiyer

Are you sure you are rapping the string in the right direction? I did this on one of my trimmers and the auto feed wouldn't work. Just a thought.


#7

A

Auto Doc's

I went back and studied the picture for your spool with the cutter string on it. The starting tip of the string is inserted into the wrong hole.

If you look closely, there appear to be a small piece of old red cutting string is in one of the pyramid shapes hole down inside. That suggests to me that it where the end of the string should be inserted then run to the outside and wound around the spool.

Also note the notches cut in the out edge of the spool, they are used to hold a short section at the final wound end of the string, so the spool can be reinserted.

Once inserted on the drive section gently tug on the cutter string end to pull it out of the groove and enable it to bump feed.

Hope this helps you.


#8

A

anthonyjaycorman

OldDiyer said:
Are you sure you are rapping the string in the right direction? I did this on one of my trimmers and the auto feed wouldn't work. Just a thought.
Click to expand...
I think so - it looks like the natural direction for the feed.


#9

A

anthonyjaycorman

Auto Doc's said:
I went back and studied the picture for your spool with the cutter string on it. The starting tip of the string is inserted into the wrong hole.

If you look closely, there appear to be a small piece of old red cutting string is in one of the pyramid shapes hole down inside. That suggests to me that it where the end of the string should be inserted then run to the outside and wound around the spool.

Also note the notches cut in the out edge of the spool, they are used to hold a short section at the final wound end of the string, so the spool can be reinserted.

Once inserted on the drive section gently tug on the cutter string end to pull it out of the groove and enable it to bump feed.

Hope this helps you.
Click to expand...
I'll take another look - not seeing anything red in the photo, but where I see the cord inserted at the top of the photo isn't where I feed it out - I feed it out off the spool. I align the notch with the feed hole and then clip the hub back on, on the assumption that those notches catch and feed the string out through the hole - is that correct?


#10

A

Auto Doc's

Once the cutter spool is installed, you pull the loose end out of the (temporary) holding groove through the outer hole so it can feed as needed when the center is bumped on the ground while cutting.

Maybe a local small engine shop can give you some direction by looking at it.


#11

A

Auto Doc's

Maybe this will help if you enlarge the page view:



#12

A

anthonyjaycorman

Auto Doc's said:
Maybe this will help if you enlarge the page view:

Click to expand...
That is incredibly helpful - thanks!!


#13

A

anthonyjaycorman

I wonder if I've got the right spool - the replacement part here: https://www.partselect.com/PS101659...ourceCode=1&SearchTerm=ST4000&ModelNum=ST4000

...is stamped with a part# 2015 208F, and mine is stamped 2019 36. The stem it sits on is flanged, but there's nothing in the spool to catch those flanges and turn it.


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