CB750 Racer Fan: The 650 motor I have has many problems with it, pistons stuck, rust, and damaged fins, plus I parted some of it out. It just isn't a viable option to use any more. I think I just like the look of the 550's top end over the 650 to much to do the 550 on steroids option you are suggesting.
Stev-o: I jumped the gun and disassembled the bikes a little while back so I couldn't try the "rocking method" but I did put the ATF/Acetone mixture you suggested to good use as you are about to read:
First thing I did once getting bikes #2 & 3 home was to disassemble both of them completely, mainly for easier storage but also to get access to both engines. I was unaware of the technique that Stev-o suggested before I did this (oh well, next time). On the bikes if one had something broken, the other had it in relatively good and working order so I shouldn't be lacking much for bike #2's build except for an exhaust. I will worry about that when the time comes.
Bikes positioned for tear down:
All the little parts:
Next goal was to get both engines freed up so I pulled the top ends off, down to the cylinders and let them sit with the ATF/Acetone "cocktail" for a couple of days. I had to cut the cam chain on both with a Dremel (I love those things, if you don't have one in your garage you should). For engine #2 I took the cautionary route.
Only a couple of the pistons were actually stuck to the cylinder wall so I was able to separate the jugs from the base. From there I was able to run a ratchet strap between the jugs and crankcase and suspend it from the ceiling so that gravity helped me as I beat on top of the stuck pistons with a block of wood and dead blow hammer.
*Sidenote: I suspended the engine through the accidental attic access I made when I put my lower half through the ceiling about a month back:
I only suspended the motor about an inch off the ground and every now again I would have to crank it a notch. Little by little the pistons gave up their stranglehold. This process although successful was long and tedious.
Getting engine #3 unstuck was much more exciting. It was all lawns chairs and gasoline thanks to member swan and his "How To" guide on setting motors on fire....on purpose
http://forums.sohc4.net/index.php?topic=84354.0. I was hesitant to use this technique on my good engine but after that one took a good hour or two of manual labor, I was ready to take the lazy way out.
Engine #3 not on fire:
Engine #3 on fire:
We sat and watched the fire/oil combo work it's magic for about 30 minutes or so:
All it took after that to break the pistons loose was to fit a wrench to the bolt that holds the rotor on and hit it with a rubber mallet. I would suggest at this point in the game you keep the engine secured so burning hot ATF doesn't come splashing over the side of the jugs on you. The constant threat of this made things interesting but I managed to free the pistons with minimal effort and no burns.
Despite my previous doubts, I was able to accomplish the mission at hand and free up both engines in a day. Not bad for a self-taught mechanic. My goals for the upcoming week is to work on understanding and separating the crankcase on engine #3. I also have three racks of carbs that need to be disassembled, cleaned, and powder coated sitting on my work bench. Decisions, Decisions.......
