I bought this 2009 klx250s with 3500 miles on it a couple months ago. I wanted to get shinko 705 tires put on so I brought it to the highest rated motorcycle mechanic in my area. Dropped it off and the tires and they swapped them and the tubes for $270. I rode about 5 miles and the back tires tube let all the air out. I called them they picked it up charged me another 170 said the back tire was fixed I rode for a couple days and again the bag tire went pssssshhhhhh and let all the air out. What could be causing this? I've spent over 450 dollars on just putting the tires on not the cost of the tires. I got the size everyone recommended.