Topic: Broken 5mm bolt in engine case.

[Old Moe Toe]

Taking my cases apart today on my 750F2 one of the 5mm bolts at the front of the engine broke off leaving only about 3mm of the bolt above the threaded hole. Tried some wd40 with multi grips, then a heat gun with multi grips but it did not feel like the broken bit was going to undo without ruining the 3mm proud bit. I have never used an eazy out with success, usually end up with a broken easyout in the centre as well as the broken bolt so gave up on it for the day.
Wondering how much you can heat up the engine case in a local area without it warping the case?. The heat gun I have could heat the case a lot hotter than I had it today.

[bryanj]

I hope you mean 6mm bolt not 5 and you can heat the case quite a lot, use WD whilst hot but be prepared for smoke and flame. easyouts wont work only answer if the molegrips don't work is drill out and helicoil

[madmtnmotors]

I hope you mean 6mm bolt not 5 and you can heat the case quite a lot, use WD whilst hot but be prepared for smoke and flame. easyouts wont work only answer if the molegrips don't work is drill out and helicoil

Agreed. I usually start with a Dremel to create a center divot on the broken bolt. A small round diamond stone will allow you to move the divot around until you get it where you want. I've never had much luck with using a center punch to create a divot, they end up off center for me every time. After getting a center point I will start with a small left hand drill bit and keep stepping up in size until the broken bolt is freed or until the threaded hole is compromised. Once the threads in the hole are compromised it's just a matter of drilling out the rest of the bolt and doing a Helicoil repair. 6mm Helicoil repairs are easy and quite common, so much so that I keep 6mm Helicoil repair threads on hand (along with many other common sizes).

[Jerry Rxman Griffin aka MuthaF'er]

The easyout you use should be damn near the diameter of the bolt. How do I know?!