# Long bolt holding muffler bracket on MTD



## Dannoman (Jan 16, 2018)

I'm glad I saw it before it fell out. A long bolt (about four inches long) was hanging loose on the muffler - the top one. It bolts up against it and holds the locking plate which secures the muffler. The top one was real loose so I attempted to screw it back in by hand and it took quite a few attempts to get it started then I tightened it up good with a wrench. That's the first time that bolt ever got loose like that. 

Good old Donyboy has a video about just what I went through.


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## Rickster55 (Dec 11, 2017)

Donyboy is my guru!


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## Vermont007 (Mar 29, 2015)

I had a similar problem early in the life of a 10HP Tecumseh, and one of the Muffler Bolts actually fell out; I found it laying on my garage floor. It appeared that the "tabs" hadn't been properly bent at the factory; but Tecumseh is gone now, so there's no one to complain to.

When I went to re-insert the unusually long bolt, I found that the threads in the aluminum head were severly damaged, and could not/should not be relied on.

Any going up in size to a 3/8" bolt will eliminate your ability to use some Muffler designs which include a structural cylinder inside the muffler which cannot be increased in diameter.

My solution was to install a 5/16" Helicoil 5521-5 like this which returned my head to a solid stainless steel 5/16' - 18 thread:










It's a little scary going through this process the 1st time; but it's well worth the effort, and it allows you to use the same 4" bolt again. I've since learned that Briggs and Stratton uses the same 5/16" - 18 thread on many of its engines, so I've been able to use some of the supply (12 ?) of the "helicoils" included in this 5521-5 kit to make repairs on them too. In addition to the Kit, you do have to have the appropriate sized drill bit, and a handle for driving Taps to thread the hole.

Here're some more specifics and what constitutes the Helicoil 5521-5 Kit:

https://www.handsontools.com/HeliCoil-5521-5-Coarse-Thread-Repair-Kit--516-18-x-469_p_9178.html?gclid=EAIaIQobChMI0ZrnvaSg2QIVHLjACh17zQhHEAQYAiABEgInFvD_BwE

I guess it pays to periodically check those "tabs" and avoid this problem altogether !


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## RedOctobyr (Mar 2, 2014)

Good advice. I had one of these start to loosen on an engine of mine, and similarly found the threads were now sloppy. Fortunately, the threads were still usable, so redoing the plate was enough to make it hold again.


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## HCBPH (Mar 8, 2011)

I've had a couple of bolt holes for muffler, intake and start motor mounts that needed refreshing before. I agree that helicoil is a good solution in many cases as long as you still have enough material to thread into.
Here's an option if you have a drill press to secure it better once you're done. Take the bolt and put a nut on it so it can fit flat on the drill press table. Clamp it down and carefully drill a small hole through one of the flats of the head, all the way through and do that to both bolts. You can then safety wire it and pretty much never worry about it falling out again. A little stainless steel wire goes a long way on securing something like this.


PS some of the helicoil kits include the corresponding drill bit in the kit, so there's no guessing whether you have the right one or not.


Just a thought here, it's worked for me.


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## Vermont007 (Mar 29, 2015)

Re-thinking this process, and having talked to others who've performed it, I'm reminded of one special precaution.

Drilling into aluminum is remarkably fast, like dealing with Balsa Wood; so it's easy for the drill to get away from you and overshoot the depth of the hole and drill too deep . . . . like into the combustion chamber (which wouldn't be a good thing).

So when I did these, I try to remember to check the depth of the tapping before I even start, and then mark my drill bit with a piece of tape to indicate the limit of how deep I want it to penetrate the already existing hole . . . . and be able to STOP before I go any deeper.

I usually vacuum these tapped holes out; but I've found that a Q-Tip gets the bulk of the shavings out; and though it's probably overkill, I do put a drop of High Heat Loctite on my Bolt when it is inserted into the helicoil.

So far, so good !


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## Dannoman (Jan 16, 2018)

Vermont007 said:


> I had a similar problem early in the life of a 10HP Tecumseh, and one of the Muffler Bolts actually fell out; I found it laying on my garage floor. It appeared that the "tabs" hadn't been properly bent at the factory; but Tecumseh is gone now, so there's no one to complain to.
> 
> When I went to re-insert the unusually long bolt, I found that the threads in the aluminum head were severly damaged, and could not/should not be relied on.
> 
> ...


Good stuff. Thanks a bunch!


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## Dannoman (Jan 16, 2018)

I wonder if I used Loctite before the threads get chewed up too much if that would prevent further damage...


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## Motor City (Jan 6, 2014)

Dannoman said:


> I wonder if I used Loctite before the threads get chewed up too much if that would prevent further damage...


No, due to the heat, the Loctite is useless.


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## HCBPH (Mar 8, 2011)

Vermont007 said:


> Re-thinking this process, and having talked to others who've performed it, I'm reminded of one special precaution.
> 
> Drilling into aluminum is remarkably fast, like dealing with Balsa Wood; so it's easy for the drill to get away from you and overshoot the depth of the hole and drill too deep . . . . like into the combustion chamber (which wouldn't be a good thing).
> 
> So when I did these, I try to remember to check the depth of the tapping before I even start, and then mark my drill bit with a piece of tape to indicate the limit of how deep I want it to penetrate the already existing hole . . . . and be able to STOP before I go any deeper.



Here's a suggestion - use a drill stop. Most times you won't have a drill stop to match the required drill bit but you can easily make your own. Take a piece of wood (like say a 3/4" dowel) and drill a hole down the center of it. With your bit in the drill, mark how deep you want to make the hole on the bit with a marker or tape. Next measure from the chuck down to that point and cut you wood piece to that length. Slip it over the bit, confirm your measurement and drill away. Although the only absolutes in life are death and taxes, it's pretty hard to drill beyond your desired depth this way. Even if the bit should grab, you can't go beyond your desired depth with something like this.


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## chargin (Mar 29, 2015)

Check the non thread part of the bolt also and make sure it didn't lose any diameter from bouncing around.

After I bought a new muffler I ended up having to buy a new lockplate and bolts.
I should have bought them all at once.


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## Toro-8-2-4 (Dec 28, 2013)

if you get stuck you can always make your own lock plate out of some galvanized sheet metal. I have done that in the past. It may not look as good but it works and you can do it pretty fast.

There are high temp thread lockers out there but I would shy away. The block is aluminum and you are at risk of stripping the threads if you need to remove them.

The lock plate is a safe and reliable way to keep the bolts in place.


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