Keep Losing Motor Mount Bolts

[MowingMojo]

I have an older model Murray riding lawnmower with a Briggs & Stratton engine. The motor mount bolts keep working themselves loose and falling out. I'm getting tired of replacing them. Last round only lasted for two mowings. Any recommendations for keeping them in?

 

[Scrubcadet10]

Is it a nut and bolt, or the self tapping, screw into the block type?
I'd say Blue loctite ought to do it... but i wonder if there is something up with engine causing excess vibration loosening them?

 

[bertsmobile1]

The ones where you can get a nut on the top drill out and fit a nut with a high tensile spring washer each end.
Mower companies use self tappers because they are cheap and in particular cheap to install .
The holes will be flogged out if they are falling out this quickly so no goop is going to keep them in.
Some times you can get away with a variation of the match in a hinge screw trick by shoving some full soft copper or aluminium wire up there then screwing the bolts back in.
Otherwise the engine will have to come out and the holes mechanically cleaned then chemically cleaned .
After that you can use the thread restoring resin of your choice but Davcon beats them all hands down
After that you need to put a tight fitting washer between the engine & the mower floor so as you tighten the bolts the goop has the washer to bear against rather then extruding back out the hole .
By not the bolt holes in the mower itself are most likely quite oval as well and probably have welts that will need to be ground off so the engine sits flat against the frame.

 

[MowingMojo]

Is it a nut and bolt, or the self tapping, screw into the block type?
I'd say Blue loctite ought to do it... but i wonder if there is something up with engine causing excess vibration loosening them?

Pretty sure they require a nut because it goes all the way through. That's what I used last time anyway.

 

[MowingMojo]

The ones where you can get a nut on the top drill out and fit a nut with a high tensile spring washer each end.
Mower companies use self tappers because they are cheap and in particular cheap to install .
The holes will be flogged out if they are falling out this quickly so no goop is going to keep them in.
Some times you can get away with a variation of the match in a hinge screw trick by shoving some full soft copper or aluminium wire up there then screwing the bolts back in.
Otherwise the engine will have to come out and the holes mechanically cleaned then chemically cleaned .
After that you can use the thread restoring resin of your choice but Davcon beats them all hands down
After that you need to put a tight fitting washer between the engine & the mower floor so as you tighten the bolts the goop has the washer to bear against rather then extruding back out the hole .
By not the bolt holes in the mower itself are most likely quite oval as well and probably have welts that will need to be ground off so the engine sits flat against the frame.

That sounds like a lot of work for a used mower I paid $300 for, but good info to know.

 

[bertsmobile1]

Your mower, your money.
A fairly common problem with mowers where the owners do their own maintenance by putting fuel in the tank and changing the oil every 10 years weather the mower needs it or not .

 

[MowingMojo]

Pretty sure they require a nut because it goes all the way through. That's what I used last time anyway.

Is it a nut and bolt, or the self tapping, screw into the block type?
I'd say Blue loctite ought to do it... but i wonder if there is something up with engine causing excess vibration loosening them?

Had to do some digging, but it looks like it is a self-tapping screw. Ordered some replacements and will see how those do before trying the Loctite. Thanks for the suggestion.

 

[MowingMojo]

Your mower, your money.
A fairly common problem with mowers where the owners do their own maintenance by putting fuel in the tank and changing the oil every 10 years weather the mower needs it or not .

 

[MowingMojo]

Could be. I bought it used so I have no idea what kind of maintenance the previous owner performed, but the guy I use now keeps it running well. Hopefully the new screws will work, with the copper or aluminium wire if necessary. Thanks again for the suggestions.

 

[Suzie]

I have an older model Murray riding lawnmower with a Briggs & Stratton engine. The motor mount bolts keep working themselves loose and falling out. I'm getting tired of replacing them. Last round only lasted for two mowings. Any recommendations for keeping them in?

Did this work for you, my mount holes on my frame have gotten bigger due to vibration, all 4 the engine is off everything is off the frame was going to take it to a welding place and see if they can fix, also my holes have to be retreaded one is hugh