Maybe pull the head off to see where exactly the piston is stuck.... Do you have any Kroil or Marvel Mystery Oil ??? Have you tried using a little heat???

I think I have marvel mystery oil somewhere. I'll get some or kroil if not. No I haven't used heat yet.... or pulled the head off - I think piston is near the top.

Time for another re-post of how I unsiezed my GT550 without stressing the crank.

Alan, have you ever pulled any teeth out ???

No, but I might have to adopt the same technique to remove the rotor from my RD400C. I'll post photos if I do.

Hmm.. may have to recreate this photo with the RT1M . I have the same exact hoist!

Are you sure it’s the piston that is stuck? I have been in a similar situation and have seen one where the flywheel sheared the key and damaged the stator into a ball of metal inside the flywheel causing it to lock up, could also be a issue in the transmission, wouldn’t hurt to pull the engine covers off both sides to verify?

Yeah, this is a good idea to look into - easy and seems like needs to be done anyway. The trans and shifting seems funky too, so this thing may be grenaded inside. It's been apart before too it seems.

Finally had some more time to mess with the RT1M in april.   My good friend Greg (also on here), came up and we worked on my 71 DT1 first, and it was an easy fix- loose ignition wire after installing rebuilt magneto - So.....we moved onto the RT1M - still stuck.    I pulled the carburetor and Greg offered to disassemble and soak it and put in the kit - while I removed the head to see how bad things looked inside....  well, as soon as I finished removing the last nut from the head, everything shifted- and loose came the piston.   I backed it down and put some grease to catch any chunks and cleaned the cylinder.  Back together it went and the compression felt great!   Running out of day - we put the carb on - did a quick pre-mix and borrowed one of my DTs tanks and tried starting it but I think we have weak or intermittant spark - so thats next.   Was fun and she's free now and seems to cycle thru gears.  

Looks like ya having a bundle of fun there. Good on ya.