Re: flyweel key welded in place
If iwombat's suggestion doesn't work, here's an excerpt from a post by CATransplant from some time back. Excellent.
My real problem was getting the sheared off key out of the crankshaft. It had pretty much welded itself to the crank and smeared itself on the crank taper besides.
Now, I've encountered that before, so I knew what to do when a key is partly smeared and welded. It might prove useful to someone else here, so I'll run through it, step-by-step. You'll need a flywheel holder. Don't try to make do with a cheap-o strap wrench. You'll just bust your knuckles. Go to the auto parts place and buy a real flywheel holder. $15 should be about what it costs. Kragen and other discount parts house are the place to go. You don't need the Pro model...you're not going to be using it that often:
1. Use a fine-cut mill file VERY CAREFULLY to file the key so it is flush with the crankshaft. The key is much softer than the crankshaft, so a light touch will keep you from cutting the crank's metal. When you reach the same level as the crank, you'll see the edges of the key. Avoid biting into the crankshaft metal. It's not that hard to do if you work slowly and lightly.
2. At that point, take a small, GOOD, 3/32" or 1/8" pin punch, and gently tap the key at the bottom of the keyway. If you're lucky, it will roll out partway and you can use a good pair of diagonal cutters to grab it and remove it. If it doesn't move, continue to step 3.
3. If step 2 doesn't work, you'll need to remove the plate that holds the points and coils. You don't have to remove the wires...just set it aside. Then, use a small centerpunch to lightly punch the exact center of the key in three places. Wrap a rag around the crankshaft to catch debris, then use a 3/32" NEW high speed steel or titanium drill bit to drill three holes in the key, using only moderate pressure and medium drill speed. The holes should be at the center, then about halfway from the ends of the key. Keep the holes straight. The soft key material will spiral out of the hole you're drilling. When that stops, you have reached the crankshaft. Don't drill any further.
4. Once again, use the small punch to try to shift the key. If it works, you're home free. If not, continue to Step 5.
5. For this step, you'll need a Dremel tool, or some other similar tool, with a fiber reinforced abrasive cutoff wheel on an arbor. Running at a slow-to-medium speed, VERY CAREFULLY grind a groove vertically down the center of the key. Cut well into the key, but stop the grooving short of the key's ends. You can use the previously-drilled holes to judge your depth. You don't want to cut into the crankshaft metal. Again, work slowly, gently, and keep the tool's speed down. Keep stopping and try to tap the key out with the pin punch as you go.
6. If the holes are drilled and it's still not coming out, EVEN MORE CAREFULLY, grind the groove at an angle from the center out, towards the edges of the keyway. Don't dig into the crankshaft. You're not trying to remove the whole key, just to relieve pressure. Keep testing with the pin punch. At some point, the key WILL come out.
7. Once you have the key removed, check the keyway closely, using a small metal scraper, if necessary, to remove any remaining bits of the key from the keyway. You need the keyway to be clean and with no remaining key metal anywhere.
8. Examine the crankshaft for any damage. If you find a burr or scratch or anything like that, you can CAREFULLY dress it down using 600 grit emery paper, followed by crocus cloth. Always work round the crankshaft, not up and down. Think of polishing a shoe with a rag.
9. Finally, use some valve grinding compound inside the flywheel and mate the two parts without the key, turning the flywheel on the crankshaft to mate the two surfaces. You can put pencil marks on both parts where they make contact. When the pencil marks are gone, you're done.
10. Clean up after yourself, making sure the crank and inside of the flywheel are spotless. No grease or oil here. Re-install the magneto plate and adjust the points to the proper setting, as per the manual.
11. Put the key in the keyway, with the bottom of the key flush with the outside of the crankshaft. The top will stick out a bit, but that's OK. Line up the flywheel keyway with the key and press the flywheel down onto the crankshaft. It will NOT go all the way down, but should not bind. Use a flashlight to make sure the key is lined up properly, then re-install the crankshaft washer (if any) and nut and slowly tighten it, using the flywheel holder to hold the flywheel still. The nut will draw the flywheel down and into its correct position.
12. To do the final torquing, make sure everthing is lined up and that the flywheel holder is very secure. One person can do this, but you must make sure everything is secure so you don't slip. It's better to pull on the flywheel holder and push on the torque wrench. Don't let your hands get too far apart, and pay attention to how you are holding the tools. If the flywheel holder slips (and it probably will), you don't want to bash your knuckles while putting over 100 lb of force on the wrench. That hurts! If necessary, take another position. As you near the proper torque, push and pull steadily until you achieve the proper torque for your model.
13. Reinstall all the other stuff, and you're done.
