I just got an 87 quadzilla 500, the kid I bought it from was riding in the winter with his summer jets and blew the top end. I rebuilt it and got it all together and rode it for about half an hour and the little rubber plug that goes into the bottom of the case to hold/seal off where the ignition wires go in came out and sounded like an old hit and miss engine, you could see the puff of air coming out of the hole. So i shut it off stuck the plug back in and tried it again because i was having fun it ran great. The after another 5 min. the engine wouldnt idle, it stayed at about 3/4 throttle, and the plug was still in. So i took the carb apart again this morning and rode it for about 30 seconds and it started reving again, and the plug came out.... i dont know why this would happen if anyone can help me please respond!

 

sounds like you have a bad crank seal on that side, which means you probably have a bad bearing also. this also means that the cases are probably wollowed out.
dont fret to loudly, this is a common problem with these beasts. all you need to do is have the case inserts put in, then new crank bearings, and of course new seals. this will mean a entire rebuild, but you will have a dependable machine after wards.
i also have a 87, so far does not need the inserts put in, but i know it will someday soon.
good luck, and enjoy the rush of good old 2 stroke power [img]i/expressions/face-icon-small-smile.gif[/img]
aaron

 

that is the only thing i could figure but i had my hopes up that is was something smaller b/c riding season just started here and my the tires for my bike are on back order and i cant ride around with studs so the zilla was my last resort..... ill have to steal my brothers nice new warrior with a yoshimura exhaust for now.

 

Yep, crank seal leaking! The reason it idles so fast is because it's very LEAN!!! Don't run it anymore or it'll go ka-boom!
Crank seals are killed by bearing/case issues as previously mentioned... Sounds like you need the traditional fix... Sorry for the not so good news.