Member Contributer interceptor69 Posted February 17 Member Contributer Posted February 17 ng to remove it that holds the clutch slave cylinder onto the engine. Now to find a bit that can back the broken piece out. Is there a bit that small? I have used them before on larger broken bolts but not something that small. Quote
Member Contributer MBrane Posted February 17 Member Contributer Posted February 17 I would soak the hole with ATF/acetone, and try a reverse/counterclockwise drill bit first. There's a good chance the heat from drilling will back the broken bit right out. If not then you have a hole for a square extractor. Round/spiral extractors are evil bits designed to make your life even harder when they inevitably break off in the hole you just drilled. 1 Quote
Member Contributer Thumbs Posted February 17 Member Contributer Posted February 17 45 minutes ago, MBrane said:. Roundwould/spiral extractors are evil bits designed to make your life even harder when they inevitably break off in the hole you just drilled. Exactly, tools of the Devil Excellent advice Quote
Rllwjoe Posted February 18 Posted February 18 In the same area I over-torqued a Crankcase Cover bolt a couple of years ago and broke it. I had misinterpreted the torque value. Anyway the stud broke off with just enough sticking out that I was able to turn it using a small chisel. I was surprised how easily it turned out. Quote
Member Contributer interceptor69 Posted February 18 Author Member Contributer Posted February 18 Thanks. I'm not looking fwd to it. Quote
Member Contributer RC1237V Posted February 18 Member Contributer Posted February 18 Just did this the other day for a friend with a KTM, he did a similar thing and spent a week trying to get it out. He brought it over, and I used a left handed cobalt bit, and put some masking tape around it to make it fit the bore snugly, and keep it centered. Used the biggest bit that was small enough to fit in the bore, and spun the drill in reverse. I stabbed it with good force, then pulled up. Did it one more time and it caught and backed it out instantly. It was too deep in the bore to try to drill with a small bit. Good luck with the repair! 1 Quote
Member Contributer interceptor69 Posted February 18 Author Member Contributer Posted February 18 On 2/17/2026 at 9:32 AM, MBrane said: I would soak the hole with ATF/acetone, and try a reverse/counterclockwise drill bit first. There's a good chance the heat from drilling will back the broken bit right out. If not then you have a hole for a square extractor. Round/spiral extractors are evil bits designed to make your life even harder when they inevitably break off in the hole you just drilled. Thanks. What size drill bit would u try? That's a small bolt. Quote
Member Contributer MBrane Posted February 18 Member Contributer Posted February 18 One about 2/3-3/4 the size of that bolt which I think is a M5. You don't want to cut into the threaded area of the case or you'll be in the Heli-Coil zone. Those work well too if 5h1t goes sideways, but more work. https://www.mcmaster.com/ Spendy, but good quality/fast shipping. 1 Quote
Member Contributer interceptor69 Posted February 19 Author Member Contributer Posted February 19 11 hours ago, MBrane said: One about 2/3-3/4 the size of that bolt which I think is a M5. You don't want to cut into the threaded area of the case or you'll be in the Heli-Coil zone. Those work well too if 5h1t goes sideways, but more work. https://www.mcmaster.com/ Spendy, but good quality/fast shipping. Thanks. 1 Quote
Member Contributer RC1237V Posted February 20 Member Contributer Posted February 20 The bolts in that area are 6mm diameter, and 90mm & 95mm according to the parts diagram. The longest left hand drill bit that will not mess up your threads is the 5mm left hand cobalt, which is 92mm. Measure what is left of your bolt, and make sure you have enough to grab onto with your drill. Luckily there should be no tension on the broken piece, and you can also subtract the thickness of the slave cylinder mounting flange - make sure it is not on the bike, you need all the room you can get. Put the drill bit all the way in before hitting the trigger, so if there are exposed threads, it will center itself. Do not spin the drill forward, or it could drive the broken-off piece deeper. Once it clears the threads you will need a thin magnet on a stick, or some sticky grease on the end of your broken bolt to retrieve the broken nub. With some luck, and patience it should come right out! McMaster part number is: 3474A56 1 Quote
Member Contributer Dutchy Posted February 20 Member Contributer Posted February 20 U could consider... get a length of 6mm threaded rod and see hom many mm it will "grip" inside the hole to assess where the broken bit sits. If you have say 4+mm thread for the rod to sit, cut the rod to size. Fit the slave (there are still 2 regular bolts) and put 2 nuts on the rod. McGyver 2.0 Quote
Member Contributer interceptor69 Posted February 20 Author Member Contributer Posted February 20 6 hours ago, Dutchy said: U could consider... get a length of 6mm threaded rod and see hom many mm it will "grip" inside the hole to assess where the broken bit sits. If you have say 4+mm thread for the rod to sit, cut the rod to size. Fit the slave (there are still 2 regular bolts) and put 2 nuts on the rod. McGyver 2.0 You know,, I thought about that but thought the idea ridiculous. Maybe it isn't. I will probably try the abovementioned technique suggested by @RC1237V first and if that doesn't work will attempt your McGuyver trick! Quote
Member Contributer interceptor69 Posted February 20 Author Member Contributer Posted February 20 10 hours ago, RC1237V said: The bolts in that area are 6mm diameter, and 90mm & 95mm according to the parts diagram. The longest left hand drill bit that will not mess up your threads is the 5mm left hand cobalt, which is 92mm. Measure what is left of your bolt, and make sure you have enough to grab onto with your drill. Luckily there should be no tension on the broken piece, and you can also subtract the thickness of the slave cylinder mounting flange - make sure it is not on the bike, you need all the room you can get. Put the drill bit all the way in before hitting the trigger, so if there are exposed threads, it will center itself. Do not spin the drill forward, or it could drive the broken-off piece deeper. Once it clears the threads you will need a thin magnet on a stick, or some sticky grease on the end of your broken bolt to retrieve the broken nub. With some luck, and patience it should come right out! McMaster part number is: 3474A56 Thank you for that detailed instruction. I believe I can get it out if I can get that bit you mentioned. Again, thank you to everyone who responded. Great forum here! Quote
Member Contributer interceptor69 Posted February 20 Author Member Contributer Posted February 20 One more thing. Why do u guys think that bolt broke off when I tried to remove it? I remember using a torque wrench when tightening those bolts a few years ago. Is there something I should use when tightening the new bolts to prevent this from occurring again? Quote
Member Contributer MBrane Posted February 20 Member Contributer Posted February 20 Could have been overtightened previously then cracked from heat cycles/vibration. Your just the "lucky" one who got the break. Could have been a flawed fastener from the start though that's rare on these bikes. FTR I never use a torque wrench on those bolts. Just a 1/4" drive ratchet gripped at the head with my hand set to snug. Haven't had one back out or break yet. 1 Quote
Member Contributer Thumbs Posted February 20 Member Contributer Posted February 20 2 hours ago, interceptor69 said: One more thing. Why do u guys think that bolt broke off when I tried to remove it? I remember using a torque wrench when tightening those bolts a few years ago. Is there something I should use when tightening the new bolts to prevent this from occurring again? Copper grease or engine oil on the threads will stop cold welding, which appears to have happened 1 Quote
Member Contributer interceptor69 Posted February 20 Author Member Contributer Posted February 20 I couldn't find that particular size bit at HD or the usual stores so ordered from McMaster-thanks for the info so I could get this done. 1 Quote
Member Contributer RC1237V Posted February 21 Member Contributer Posted February 21 If the Mc Master bit does not work, no there are no threads left to engage a threaded rod, you only choices are to lay the bike over gently and get some JB Weld mixed up and drizzle it down the hole and insert said threaded rod and wait a day. Make sure you put the slave cylinder on with the other bolts so that the threaded rod centers in the hole it is supposed to line up with. Not sure from the diagram, but if the bolt goes through the "Change Cover" (Item #3) you could drill and tap the hole in that cover for a Helicoil, or Time-Sert and just use a short bolt and be done with it. Keep us posted... 1 Quote
Member Contributer interceptor69 Posted February 28 Author Member Contributer Posted February 28 be a simple drill bit, just reversed. Is this what I need to drill the bolt out? Quote
Member Contributer interceptor69 Posted February 28 Author Member Contributer Posted February 28 The drill bit arrived and it appears to be a simple reverse drill bit. Doesn't look like the one I've used before but that was a spark plug that broke off in the motor. Is this what I need to drill those out? Want to make certain before I truly screw this up. Quote
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