Well my 2000wr 400 (converted to yz) wouldn't start yesterday because it wasnt making much for compression. I could push it over by hand. So today I started to tear the bike apart and found the exhaust was completely packed with sunflower screenings( we feed them to el cows) all the way to the valves. I pulled of the cylinder head and much to my dismay the piston looked like a charcoal firepit. . I ran the bike on sunflower seeds. I guess you could say its a failed bio fuel experiment lol. The cylinder looks great, and I can still see the crosshatching. This bike has never been rebuilt and ran great. I'm going to send the head in and have them go through it because i'm not sure why I was losing compression. The piston rings seem ok. When I pulled the spark plug it almost appeared to have antifreeze on it so I was wondering if it could be the head gasket. Now for the question section. 1.Would it be a good idea to replace the piston.( it appears that the cylinder would only need honing.) Even if the ring endgap checks out withing specs? 2.While i'm in here I was wondering what i could do fore mods.( I love power) I know the yz runs like 12.8 to 1 and my wr runs like 12.5 to 1, but isnt the connecting rod and the wristpin hole larger on the wr's. What kind of piston should i buy? stock or wiseco or...I want to be able to run 91 octane which i have been. Do they make a 12.8 to 1 to fit my wr. I've already yz timed so i'm not sure if theres much else to do besides hot cam. 3 BIG BORE option. What would it cost to get an oversized cylinder and piston?Thanks for the help and remember next time you see a mouse kill that little b@$%^&%^.