# Briggs 21hp Broken Head Bolt



## fan1080 (May 26, 2017)

Hi folks!

I just replaced the head gasket on my Briggs 21hp OHV engine. While doing so, I broke the head bolt on the bottom right, which is the right hand outside edge of the push rod chamber. 

Engine is running fine, but I'm not certain if it is a good idea to keep running it with this broken bolt. I'm not a small engine mechanic, so could someone clarify if this is something that needs to be fixed? Would it be more of a concern if it was a bolt around the compression chamber as opposed to the push rod chamber, or are both just as important?

Thanks for any assistance.


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## AVB (Nov 28, 2014)

Well these 21 are bad to blow gaskets even with all the bolts in place so yes I expect you will again blow the head gasket in short order. That bolt needs replacing. In order extract that the broken one it need to drilled out and then tapped for helix coil or other thread repair device and a new bolt installed.

The old bolt is probably galled is nearly permanently in the engine and the normal bolt extractors will only break off which is then even harder to remove. I have broke several trying and end up using a carbide drill bit to remove them. I no longer try the extractors and just drill out in the first place.


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## fan1080 (May 26, 2017)

Thanks for the reply, AVB.

When I broke the bolt, I immediately lost interest in continuing the repair and just put the mower away.

I purchased the bolt yesterday, along with some bolt extractors. Armed and ready for the repair, I unenthusiastically began this morning. Hoping for the best, yet expecting the worst.

Well, to put it mildly, I got very lucky!

I figured before pulling everything apart again I might as well try removing the bolt I broke (I just left the bolt in place before putting the mower away). I put a socket on it and gently turned it to remove it. As luck would have it, the bolt didn't snap completely in two, it was mostly stretched/cracked. It came out really easily, in one piece.

I'm sure that's not the norm, but I'll take it. 

I put the new bolt in and all seems good.

Thanks again for your reply.

Cheers!


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## AVB (Nov 28, 2014)

Sounds like you had over torqued it on installation.

For me I usually break them on removal due to galling from aluminum transfer. This usually around the exhaust port. Sometime I can work them back and forth until can remove them but usually then the threads in the cylinder are messed up. Then I need to go though a thread restore procedure.

Anyway glad to hear you were able to remove the broken bolt without problems, just very lucky fellow.


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