Snapped mounting stud please help ASAP


New Member
Mar 27, 2017
Vibration caused one of my back mounting studs to snap at the face of the crankcase. I tried using an extracting bit with a drill and after that didn't work tried using a dremel to cut a slot so I could use a flat head to back it out. Neither worked and chewed up the opening of the hole pretty good in the process. Any ideas on how to get the bolt out? Should I give up and get a new motor? Maybe get a new crankcase (and if so where)? Here is some pics to help (I removed the other stud next to the broken one in the pic)



Well-Known Member
Sep 30, 2012
look in the "Mounting Techniques for Bicycle Motors" area - there are lot of other ways to go - I like the angle iron ways as the case metal often gets pretty soft after trying to get a stud out

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New Member
Mar 22, 2017
Baltimore , MD , USA
Try to open the whole wheel system. There are 4/5 bolts outer sides. Try to open the bolts first. Then you can see the inner part of the system where bolt you are trying to loose can be seen and may get an easier way to free it.


Active Member
Jan 8, 2016
Mpls Mn
Bummer, Looks like a nice chrome engine also...I guess at this point I would drill and tap a totally new hole as close to the clutch cover as possible and adapt the mount bracket to accommodate the new width of the stud spacing and see if it holds. Those original studs are super soft. If your time is valuable then get a new engine and you will have your old for new parts and you can use some of the chrome covers again. Either way is no fun. Crassius angle iron way is another good way. Or use both methods for a double strong mount!


New Member
Aug 13, 2011
Eustis FL
The slot you cut for a flat blade screwdriver probably hurts more than helps. The dremel wheel doesn't just remove metal, it also displaces and moves it around which has staked the screw in making it harder to remove.

You should have drilled it out, starting with a very small drill bit and slowly going larger one drill bit size at a time. Leave enough of the screw's shell for an extrator to "bite" into without also biting into the hole's threads you want to save. If it were a Phillips slot to begin with, it have centered your bit. A broken bolt or Flat blade slot will make it harder to center but it can be done. Center punch it before drilling. It needs to be centered so you don't damage the threads. With a hole all the way through the center of the screw, the tension on the threads is reduced and the remaining "shell" will come out easier with a good extractor.

If I were you, I would drill and extract. Don't drill all the way through unless your sure it's centered. Go to Lowes and get a Grabit extractor, get the pack with 4 sizes, tools are an investment.
You will also need a reversible drill. A 3/8" drill will back out small screws, larger screws will need the torque of a 1/2" drill to back out. I find the Grabit drill bit end doesn't work all that well so I use a regular drill bit of about the same size. Yesterday, I tore down an old Honda 350 twin that had 20 side cover screws. I used the proper JIS screwdrivers (not Phillips head although they look like it). The JIS drivers still cammed out of 5 of the screws. If I had used a Phillips driver the number would probably been 18! The Grabit extractors removed the stripped and stuck 5 screws. I did have 1 screw that needed the center of it drilled out to take some thread tension off

In the future, use penetrating oil on bolts/screws and get an impact screwdriver if you have remove screws to removing for the first time. A little more work to start with but a whole lot of grief and time saved in the long run. For penetrating oil, I have used Kroil and PB Blaster but I seem to have more sucess with Liquid Wrench.

Good luck with it.
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