I have a MK55 and #4 is STUCK, I can’t even get the plug out. I know the block is probably junk, crank too. But the other pistons, reeds look great. I guess about my only option is to get the plug out? The piston is about 2/3’s of the way to TDC, so no ports are open. I would like to save what isn’t junk and get more than 3 cents a pound for all that aluminum block.
Split the crankcase. Remove as many rod caps as you can. Being #4, you might able to access rod bolts via removed end cap. Once the crank is out of the way, you might be able to drill out the buggered piston. Break it up,collapse it on itself. Might save the block!
I recently had the exact problem on the exact same model power head. I ended up cutting the block off the piston with a hack saw. Honestly, I did. As it turned out, the crank was junk, too. In times like that, it gets to be a challenge of mind over matter, rather than a practical exercise.
Got the plug out – parked my truck on top of the block and used a 1/2" drive breaker bar, started soaking with PB Blaster today. Think acetone & tranny fluid will do anything? How many days soaking? At least the ports are closed!
Started with blaster 8 days ago, added tranny fluid & acetone 7 days ago, fluid level hasn’t gone down that I can tell, piston still dry looking through the intake and exhaust ports. Hmmm, maybe I can get at the conn. rod with a sawz-all.
Is the piston above the ports? If so, air pressure helps if the plug threads are good. Braze a valve stem onto a plug base and apply 100 PSI or so and let stand. Should force the mix past the rings a little.
I am a firm believer in the grease gun technique. With no worry about saving block tap the
no longer good sparkplug hole to any convenient NPT thread use a bushing of that size thread with a 1/8" NPT hole in center. This is same size as hose to grease gun. A short length of pipe threaded to 1/8" NPT and you are good to go. NPT tap. bushing and 1/8 NPT pipe are standard hardware items. !/8" NPT is a common size … To avoid bursting hose I use the 1/8" NPT pipe to make a direct connection from grease gun to adapter or in this
case bushing …the check valve in pump holds pressure.
Tap might be available as rental the bushings and threaded 1/8" NPT pipe pocket change.
Once you get a stuck piston moving you can get it to ports from there you may be able to
drive it out using a hardwood dowel thru enlarged spark plug hole.
i just finished saving pistons from a KF7 with a stuck piston and a locked up with
rust crank and rod assembly.
Louis
Sleeves are cast into in block. The only practical way to separate is a device called a "Sweat" Furnace that melts aluminum but not steel.
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