Well sounds like you might have some work to do on your hands. First off sounds like you might want to check your compression. Sounds like you might need a top end. Other possibility is your silencer needs to be repacked.
As for starting if you have low compression it will be hard to start. You will also want to make sure your carb is adjusted properly. You can check this by looking into the carb you should see the slide and if you hit the gas it should go up and down. This should sit a small crack so that just a small opening is able to see through. if not the adjuster is the screw that sticks out the side of the carb. Changing the gas and plug was a great place to start. Make sure you have a good set of boots on it will help you kick the 500 hard. The biggest thing about the zilla is how hard it is to start but it just takes time and you will figure out the secret to your zilla. Maybe one of the zilla owners can help you better.
Garrgling at high RPM's do you mean when it is 3/4 to full throttle? If so your jetting is wrong in your carb. Or you need to clean your carb. You will need to take apart your carb bowl and remove the main jet and spray carb cleaner on through it or use air compressor to blow it out. My bet is needs to be cleaned.
What do you mean 2nd is slipping. Is it slipping out of 2nd gear? or just not engaging. In anycase sounds like a shift fork is bad. This is not good because you have to split the case to replace that. The part is under $100 but it is the service to get it replaced that will cost you. Unless you are confident that you can do it yourself its not that hard if you have a manual but can be kind of tricky. If you are going to have someone replace your shirt fork it is a good idea to have everything else checked out crank, bearings, gears and all.
I believe the zilla takes 1000ml it should be on the side of the case somewhere. There is no sightglass just have to measure it out.
I would go up to 93 or 94 octane the zilla likes good gas. Running 87 could also be causing it to run funny. 32:1 sounds in range for a zilla but it really depends on what oil you us.
Hope this helps you out
Jason
__________________  |