Forum - Briggs & Stratton Racing
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tfgecko

Registered: 07/15
Posts: 6
Reply with quote  #1 
My dad came off from a session and noticed one of his exhaust bolts had come quite loose. While tightening it back down the bolt snapped and now half of the bolt is in the threads and can't [easily] be backed out. Anyone have any tips for the easiest way to back this out without risking damage to the engine itself.

We were hoping to find a diagram with the pitch of the two exhaust bolts possibly to make a jig for drilling out the bolt so that if this happens to anyone else in the future we have a job for the job, but without diagrams it all comes to measurements.

Any other ideas? Have just over a month before our next race so we have time to do this properly.
ProiettoRacing

Registered: 07/16
Posts: 2
Reply with quote  #2 
The only way to do this is to drill out the remaining bolt material. Use an appropriate size drill bit and slowly drill it out until you only have enough original material left occupying the threads and then use a chaser thread tool to clean out the rest -- if you intend to use the original threads. I recommend you drill out the old bolt and threads and install a helicoil thread instead. There are kits just for this application. They are much stronger and will last the lifetime of the engine or at the very least a very long time. I have gone this way and the bolts never back out and can be tightened down to higher torque spec. without fear of snapping or damaging the threads. Let us know how it goes...
FasterMotorsFasterMotors

Registered: 06/15/11
Posts: 56
Reply with quote  #3 
If any of the bolt is sticking up above the head surface try using a vice grip to get hold of it and turn it out. Even if you only can turn it a tiny amount at a time is great. Just take your time and turn it out.
If it's broke off in the hole it will be much more difficult.
To break off a grade 5 socket head cap screw you need to really tighten it much too tight.
It may have been cross threaded or bottomed out (too long) Either way it will be very difficult to get out. If it was tightened so tight that it broke i's really going to difficult to get out!
If you have never removed broken bolts like this before you are going to get an education.
You might be better off to have some one with experience do this job for you. 
Best of luck.
If i can help give me a call.


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Jimbo
http://www.fastermotors.net
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tfgecko

Registered: 07/15
Posts: 6
Reply with quote  #4 
@ProiettoRacing do you know the specific kit you used when you did this, what thread size etc?

@Fastermotors Sadly the bolt is within the threads, it wasn't bottomed out so we suspect it got cross threaded. Won't be the first time drilling out a snapped bolt, and with access to a machine shop it shouldn't be too hard. It's simply the first time having to drill a bolt out of a motor so we're doing our research first before diving in.
FerDeLance

Registered: 11/10/13
Posts: 7
Reply with quote  #5 
I have had a similar issue. The header bolts holding the exhaust on are known to come loose from vibrations. I have had to replace them more than once. At the track, another racer was informing me that I was making a mistake using metric bolts, insisting that Briggs (being American) would only use standard/imperial. Anyway, he convinced me to re-tap the holes to 1/4-20. They held up for the next race but I will be drilling them out and using helicoils and cup point set screws as studs. Then a pair of locking nuts over the flange. I hope that works. 
I think you should drill out the snapped bolt and re-tap the hole

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