Re: Need help with repair
Well, you shouldn't mix your gas willy-nilly like that, you should put X amount 2-stroke oil in 1 Gallon gas (or multiples thereof) so your mix is right. It seems if your mix was "not a full gallon to the approx 7 oz" of 2-STROKE(??) oil then your mix didn't have anything to do with the failure, best I can figure is your mix was around 16:1, which is too much oil. That mix may make the motor run funky but it wont make the bottom end seize, it would actually lubricate it better. For the record, on a motor that is already broke in I run 32:1 mix ratio, which is 4oz oil in 1 gallon gas. Others may run more or less oil (usually less), but something around 32:1 is proper. During break in of a new motor you should run something in the neighborhood of 18:1 to 24:1 (there are lots of theories on breakin), you run extra oil for the first couple hundred miles to help lubricate the dry parts on a new motor.
Since you have the top end off and the motor is still locked up, you either have something in the bottom end gone wrong, or something wrong on the gear side of the motor. I would pull the gear side cover and take a look in there, make sure there is nothing in there that would make those gears jam. If the problem is inside the case then you are up against a lot more work, so hopefully you will find something wrong with the gears. If you have the puller tool that comes with the motor you could pull the small bevel gear, this disconnects the crank shaft of the motor from the clutch (big bevel gear). If the piston wont move freely with the small bevel gear removed then something is hosed inside your crankcase....
Since this is all speculation I wont go on further, you'll have to dig in and provide more information on what you find. The good news is your gas/oil mix didn't kill your motor, bad news is a problem in the bottom end is not an easy fix.