I'd get some video surveillance and a shotgun handy.
I would also place no trespassing signs all over so when I booby trapped the property with spike pits, I wouldn't get sued.

 

Where the heck do you live Jonny? We never loose gas and leave the keys in our outlander while its parked at home...

 

Well, 1st off, welcome to the site.

It almost sounds like you know who these people are that are siphoning your gas. One way to deal with this is to not leave any gas in your tank. When your finished riding, siphon it out and securly store is somewhere else.

As for the rats, there is always trapping them or there are natural rat replellents that you can try:

• Peppermint oil, which has a strong smell that rats hate. You can soak some cotton balls in peppermint oil and place them in areas where rats are likely to appear.
• Cayenne pepper, which has a spicy scent that drives rats away. You can sprinkle some cayenne pepper powder around your house or garden to deter rats.
• Bay leaves, which emit a scent that rats cannot stand. You can scatter some bay leaves in your pantry, cabinets, or drawers to keep rats from nibbling on your food.
• Ammonia, which is a powerful cleaning agent and a repelling agent to rodents. You can mix some ammonia with vinegar and spray it near potential rat entry points.
• Moth balls, which can repel both rats and mice. You can crush some moth balls and mix them with dish detergent and water, then spray the solution around your house.

 

I'd leave it with a full tank....of diesel!

 

not sure if you will find a locking one that will work. There is no lip on the filler neck for it to lock against, you will have to find one that does not rely on a lever in the cap to lock but instead does something to the cap itself so when it turns it does not come out, similar to the child proof caps on prescription drugs.. or put something like this on it

Welcome to Fleet Oil and Truck Supply -

 

I'd go with an electric fence

 

Get a really Big dog.

 

And keep them hungry.

 

Another "Drive by Poster", he hasn't been back since he first posted 4 days ago.

 

Don't fill it up all the way if you are just going for a short ride, and never fill it up until you are ready to go.
By adding gas 2 minutes before you ride, it should stop this.
I never fill mine up until I am about to leave, but mostly because I took the collar out of the filler neck so it will hold more gas, so don't fill it up before.
Usually start it so it can warm up, then top the tank off, get my gear on, and the water temp is already up to 60 C by then, and just ride it easy until I see water temperature over 80 C.