Topic: CB500 four seized

[Icefire]

I have a 1973 CB500 four that I purchased a few weeks back that only has 9000 miles on it. The bike is basically in great condition besides the motor is seized. The original owner rode the bike until 1984 at which time he parked it. His son at some point pulled the plugs out and neglected to reinstall them ( not sure why he took them out ).
I read one of the posts here on "seized engine" and have tried the following :
A: added WD to the cylinders, rocked the bike back and forth in 5th gear, multiple times over 1 week, no success.
B: put a 50-50 mix of ATF and Acetone in, rocked the bike back and forth in 5th gear, multiple times over 1 week, again with no success.
C: tried Seafoam Deep Creep, rocked the bike with no results yet, has only been 3 days.

My next option will be to fill the cylinders with diesel fuel, which I have heard works also.
Has anyone here had any success un seizing their motor without tearing it down ?
I do not want to cut the chain to get at the cylinder and end up splitting the cases since this motor has such low mileage on it.
Would prefer to get it  loosen up, remove the head and cylinder and do a ring and hone job.
any input would be much appreciated guys.

[nicks2319]

All the seized 500s i've torn down were rusted solid in the cylinders. Took weeks of heat + pb blaster + seafoam and some force. And then the cylinders usually need honed.

[b52bombardier1]

+1 on the heat, chemistry and patience. A 1000 watt heat gun on cooling fins or maybe a propane torch if you are careful can help break those rusty internal bonds.

  I can also second the idea of using a socket at the flywheel, etc.  Don't use the kick starter for this.  You can strip the splines and cause deeper damage.

Rick

[whitjonw]

Remove the stator cover and put a breaker bar on the nut. After soaking, and with the chemicals still in, attempt to rotate the crank.

This is what I did on my '74 CB750 as well after pouring the same stuff down the spark plug holes and soaking for about 2 months. The breaker bar with a longer cheater pipe slipped over it and brute force finally freed it...and supposedly it hadn't been sitting for that long ! Of course, a DFDPO let it sit exposed to moisture without the plugs installed. Why !!!!