Continuing along with the RM250: The cylinder is relined ready for finish honing. After taking a look at the head studs, Iíve decided to replace all of the threads with Stainless Steel inserts.
The stainless alloy inserts have a small tang at the bottom to allow a way to grab while inserting.
#2 & 8 are stripping & #6 is snapped off. Take a good look at the photo and learn what to look for. After seeing all of the cylinders with blown pistons on this site, Iíll guess that there are a lot more stripped stud threads then it would seem.
Back to the snapped off #6 stud. You shouldnít just attempt to drill out a snapped stud with an electric drill. The bit can walk off of center line and cause more problems. Now we have replaced the drill press with a vertical milling machine. Instead of a drill bit, Iím using a 2 flute center cut end mill to remove the snapped stud.
The end mill does a straight down plunge and removes the stud without walking off the center.
Next, on all locations, I tap drill the hole and cut the threads.
You can see how handy the Parallel mounting plate is while working with the cylinder. No matter what the operation is, itís always a problem getting a proper hold on the Dang thing. "Trade Secrets"
Last, install the inserts in all of the threaded holes.
The top of the new liner is decked with a .005Ē squeeze fit to seal the head gasket.
The small smudge above the reed valve pocket is from my 500 deg. Temp stick. I use the temp stick to keep track of the cylinder temperature when removing & replacing the new liner.
Iíve ordered a few lengths of 8x1mm threaded rod for machining new stainless head studs. When we receive a cylinder for thread replacement, Iíll supply new Stainless head studs to go along with the job.
18 & 8 Stainless steel, 18% Chrome, 8% Nickel. "Trade secret"
After the last few cylinder repair jobs, we are starting to work from the bottom so we wonít have to disturb any existing head studs. As seen earlier in this thread, pulling head studs is a pain.
As you have learned, assembling a tool box and shop with the proper equipment can be a life long project. If your young and have the ambition, you can do this too. Never give up on your education.
All for now ďOld DogĒ