the head of the bolt broke clean off with minimal force. Must've over tightened it last time, or it corroded out. Both seem likely. Any advice on how to get it out without having to drill things out? I had it out a couple months ago, when the great flood happened, but other than that, it has been un-touched.

 

Update, got it out, it sure did break in an interesting manner.
the gouge is mostly how it was when it broke. After doing a bit of tapping with a wrench and a hole punch, I was able to free it up enough to use a small flat blade screwdriver to get it out. I don't have anything like this laying around, is there a specific part number I can use to get a replacement? Also, any ideas to how it broke in this manner?

 

You're very luck on getting it out.Probably broke the head off because of being too tight. Only takes about 5-7 foot pounds torque which is just snug. Polaris part # is 3083767. You can order one from Partzilla,ebay,etc or match this flange head bolt up at any good hardware store. Think it's a 6 mm 1.25 pitch threads.

 

Okay, thanks OPT! Also, yeah, I am really lucky I got it out, heh. Lucky for me that it was soaking itself in oil. Well, mostly Seafoam and brakekleen, actually, but there was a trace of oil too. I had taken the Cylinder head off while attempting to diagnose what had killed it this time (had died on me again), and discovered so much carbon on the top of the piston that you could build a brick of carbon fiber from it. Cylinder head was mostly spotless, it was just the piston head. No scoring or any really scratches whatsoever in there, which really surprised me, considering how hard this thing has been worked. When I was cleaning the piston head, the fluids would actually stay up on top of the piston with very little leakage, unless it was very close to exposing part of the exhaust opening. The whole time, it ended up being that the spark plug cable had disconnected from the coil. I ended up re-connecting it and used a liberal amount of glue and zip-ties after I got a good connection.

 

Did you check the piston to cylinder clearance when you had the cylinder off? Could have saved you a second time from going into the engine if you reused the same piston and rings and they decide to seize up.Cylinders and sometimes even pistons can look good but clearance may be too far if you haven't done a top end recently. .005 clearance between the piston and cylinder and the piston is considered worn out.Look at the 5:50 mark on this video.

 

No, I only had the head off. However, everything seemed right. It wasn't flopping around in the cylinder or anything.
Plus, it actually wasn't that bad to get to it, and I still have the front fender off of it until I am happy with how it is doing, just to make things easier. I have definitely had more annoying things to work with (grimaces at memory of the Artic Cat Carb adjustment process).

 

If you feel satisfied with the piston then get a new head gasket. Don't reuse the old one as the metal squish band is already compressed and may not seal properly again.Hopefully the base gasket will be ok as long as you don't rock the cylinder.