New Member here! Troy-Bilt Weed Wacker TB22 rear cover assembly (753-08557)

wrbear

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Howdy Folks! New member, first time poster. My TB22 weed eater stopped working whilst in use. I checked the electrical assembly and it has spark. I placed carb cleaner in it no luck. I did notice when I started disassembling it that the rear cover assembly had melted flattened plastic in the vicinity of the piston rod. I'm guessing it was two circular edges that created a channel for the piston edge to ride in. I trimmed the damaged area out and sealed a crack that developed with JB Weld. I think the unit would not start due to a lack of compression in the cylinder section due to the crack. My question. Before I start it, does anyone know if the channels were required to keep the piston rod from warbling? Can not having the channel mess it
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StarTech

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See if this helps as this what it should look like on the inside.
753-08557 INSIDE.png
BTW this is a fairly low cost item.
 

wrbear

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See if this helps as this what it should look like on the inside.
View attachment 56796
BTW this is a fairly low cost item.
Thanks! I had a hard time finding a shot from the inside like that. It helps me visualize the area before it melted. I'm guessing there is too much play in the piston rod connection. That is the only thing that would have made it melt like it had a channel in the molding. The two circular melted rings were probably the rod rubbing as noted in the image. it actually created a valley. This is an after with JB Weld. I think I have a bigger problem.
 

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bertsmobile1

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Well it is part of the crank case so it will get very hot
The crank should be held tight against the bearing by the flywheel on the other side so the big end journal is clear of the end plate .
If the red gasket has collapsed or it was done up way too tight then that may also have caused the journal to rub on the end plate
Final problem would be the journal itself coming loose in the counter weight.
Usually on bottom end products, the journal is basically a big rivet so once they come loose it is scrap metal
 

wrbear

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Well it is part of the crank case so it will get very hot
The crank should be held tight against the bearing by the flywheel on the other side so the big end journal is clear of the end plate .
If the red gasket has collapsed or it was done up way too tight then that may also have caused the journal to rub on the end plate
Final problem would be the journal itself coming loose in the counter weight.
Usually on bottom end products, the journal is basically a big rivet so once they come loose it is scrap metal
Thanks for the writeup on the typical issues. Yea low end but served me for 3 years. I figured I would check to see if it was an obvious and inexpensive fix. It has about 1/16" play which I think is 1/16" too much. Not sure when it get's hot. The short block assembly is bought as a unit for around $80. So, that's a no. I at least learned about them a bit.
 

wrbear

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Well it is part of the crank case so it will get very hot
The crank should be held tight against the bearing by the flywheel on the other side so the big end journal is clear of the end plate .
If the red gasket has collapsed or it was done up way too tight then that may also have caused the journal to rub on the end plate
Final problem would be the journal itself coming loose in the counter weight.
Usually on bottom end products, the journal is basically a big rivet so once they come loose it is scrap metal
FYI, Time of Death - June 4, 2021 11:10 AM CST. Well, I dug into this a bit more and discovered the problem. The pin that was pressed into the flywheel started to elongate the flywheel hole as noted in the attached image. The piston rod end ridings on bearings. Hope this helps others with this type of issue. Now to decide what to replace this with.
 

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bertsmobile1

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FYI, Time of Death - June 4, 2021 11:10 AM CST. Well, I dug into this a bit more and discovered the problem. The pin that was pressed into the flywheel started to elongate the flywheel hole as noted in the attached image. The piston rod end ridings on bearings. Hope this helps others with this type of issue. Now to decide what to replace this with.
A good reason to avoid overhung cranks on line trimers
Easy way to tell, apart from price is on a full crankshaft the pull start will be behind the engine
On overhung cranks ( except the Ryobi lawn hornets ) the pull start will be on the inside of the engine .
 
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