Throttle Stuck Open
Hello again, guys. I'm stumped again with another issue. I replaced the fuel pressure regulator, drained the crankcase, put a new filter and fresh oil in it, pulled the plugs, turned the motor over to blow the fuel out of the flooded cylinders, put in new iridium plugs, and flushed the radiator. I also replaced the fuel saturated air filter with a freshly oiled K&N filter. It started and ran fine for a while. It ran great, in fact. As I was going for a short ride this weekend, I goosed the throttle for a grin, and the grin went away pretty quickly when the engine stayed revved up. The bike wanted to haul ass, and no amount of whacking the throttle back and forth would get it to come back down. That made for an interesting and nerve wracking ride home (maybe 3/4 mile or so- kill it, coast, stop, fire it up, go, etc). Anyway, after jacking around with the throttle cables and checking the routing and everything, I pulled the throttle assembly all the way off the handlebars to play with the cables and make sure they were intact and moving as they should. The throttle snaps back as it should when released, and, if I look way down into the throttle body area, I can see the little wheel rotate as it should. It seems to snap back right to idle position as it should (visibly and audibly). However, when I fire up the bike, it wants to rev to maybe 5 or 6 grand. If I crack open the throttle, it revs higher, but doesn't come back down. It seems to me that if the cables seem to be moving as they should, and the wheel they're attached to on the throttle body is moving as it should and closing as it should, the butterflies in the throttle body should be physically closing, and it shouldn't be able to stick open, and the bike wouldn't be able to get the air intake needed to rev that high. I've searched the forum and the internet and clues, and haven't found much helpful information. If the TPS were faulty, it shouldn't be able to rev up the bike, if the butterflies are closed and it can't intake sufficient air. Apparently the TPSs almost never fail anyway. So... at this point, I suspect I may have to attempt the dreaded deed of pulling out that whole throttle body assembly, checking everything, maybe installing new cables while I'm at it, etc. Or I could just try replacing the cables and that's it- still a challenging task. Pulling the carb rack on the Yamaha 600 isn't really for the faint of heart the first time, but I've done it so many times, it's no big deal. The 919, however.... well, that looks a good bit more intimidating with all the vacuum lines and sensor connectors, and probably even less space to pull back the box and work it out the left side. I'm not really scared to attempt it. I just really, really don't want to, if it can be avoided. I know it will be a major pita. So... any ideas? Just wondering if there's a common thing that may cause such an issue, like an idle air valve or something. Thanks in advance for any input.