Need help seized engine

Hey all, long time lurker first time poster, a while back I nabbed a Seca 650rj for 25 bucks and have set to work getting it going again, the thing has been sittting something like 12 years outside but covered with a tarp on a covered porch. I've been tearing it down following the manual but I've hit an impasse. First problem is a spark plug was broken off in Cyl No. 1 the glass sheered off at the head leaving the inner glass and the metal threads behind. The second issue is it's Seized due to either sitting or some other reason as it wont turn over or even budge. So far I've popped the cover off and tried to turn it manually, and then pulled the 3 plugs I could and poured an 8oz can of kroil split among the three down the hole and have been working at it for about 2 weeks rocking the bike back and forth in the second and highest gears.

I attempted to pull the head by removing the tensioner and the valve cover but the cam chain is FAR too tight for me to pull the cams out and the bolts for the sprockets are hidden inside of the head. Any advice? Thanks!

 

Why is the broken plug hard to remove? The metal part should be enough to extract with the same socket. Have you tried some PB blaster or similar penetrating oil? I've had really good luck soaking bolts with that.
Likely, the rings are stuck in the cylinders, so soaking them in ATF or I've heard of using Coke tends to free things up if you're persistent. There's a pretty good video online that shows freeing up a Yamaha engine that was seized and the guy (after letting the cylinders soak a while) simply puts the bike in gear and rocks it back and forth to get things moving a bit. I wouldn't try forcing things. Let the chemical process work and just check it from time to time to see if it's freed up.

 

It sheered below the socket so now there's just threads in the head and some insulator plinking around in the cylinder. I figure after gaskets/labor/definitely ruined pistons and rings I might just buy a new motor. I have a guy who can get me a confirmed runner with 16k miles for like 450. I'll keep rocking the bike and working at it until I decide if I just want to replace the motor. Ill also try the coke

 

You haven't said how many miles were on the seized motor. If it's tired to begin with you might spend more than $450 freshening things up. Honing cylinders and lapping valves you can do yourself but new rings will be half that I would think, plus new cam chain, gaskets etc. etc.
To extract the spark plug get the appropriate sized square edged extractor, same as in the pic. Once you drill a hole these are hammered into place. I was successful with the same situation except in a V6 truck with the inner fender in the way. A real SOB.

 

23k on the motor. And yeah that's about what I figured, Ill probably pull the motor and break it down for spare parts then just buy the runner.

 

check to make sure if you have a mechanical or electrical tach. If your replacement motor is the other you might also have to replace the tach or do without.

 

break the chain and you can use a master link on it

then you can remove the head to have the spark plug removed

 

Unless you're into motors fun teh fun/challenge (and a lot of us are) AND the new one is a confirmed recent runner then I would buy it. It's easy to sink hours and $$s ££s in these motors, especially if it's your first time at it. You will have load of other issues to sort anyway (brakes, wheel bearings, electrics, fuel system) so you can get your fun there.

BTW if it's seized through water ingress the bores may be corroded - that means a rebore and o/s pistons -if you can find them it will be more than the cost of the motor in parts alone.

 

And if it is YICS or non-YICS. There are wiring harness differences, and carb jeting diffrences.