I have a 98 XC 700 that won't idle. When I start it up, I have to hold the throttle slightly open with my left hand. Once it running, it idle, then will die about after about 10 seconds. Could the throttle cable be out of adjustment? if it is, how do I fix it as I'm fairly new to this. or do I have to adjust it at the carbs? The plugs are a browish color color after about an hour or 2 running if you need any help.