I have a 2000 model SX700R that backfires and runs poorly after sitting over the summer months. I have ran the sled less than 1 mile since a local Yamaha dealer cleaned the carbs etc. and then put in storage. I started the sled 3 times this summer and it will not idle more than about 30 seconds and wants to quit. If I crack the throttle, it backfires, just as it did last year before the service work. Any advise, new plugs are installed. Also, what can be done to put some muscle into this sled? I have been quite satisfied for the most part when the sled is running good. Thanks for your responses.