What happened: My lovely GS450LX runs beautifully until fully warmed up (20 min of riding), when the idle rises to about 2k RPM. Today, it was hot out and I was stuck in traffic. I started worrying about overheating and I decided to adjust the idle speed. I clearly wasn't thinking very clearly because instead of getting off the bike and taking a moment to figure out what I was touching, I grabbed the large knob and gave it a little wiggle just to see how much play there was, in preparation to twist it slightly. Well, suddenly I'm idling at 2900RPM, with all sorts of top end clatter and racket. I pulled over and killed it. Luckily I was right across the street from a bike shop, so I pulled it in there and we pretty quickly found out what had happened.
In my idiocy, I had grabbed the cam chain tensioner (which in retrospect is nowhere near the idle adjust, nor does it look like it). Bad news for the timing and my valves and pistons. But how bad? One mechanic thought that because the bike was still running until I killed it that the valves might not have bent and that with a timing chain adjust and new shims I'd be ok. The other said that it was more likely the valves bent, or worse, that the pistons would be damaged or burned. After twisting the tensioner, the motor ran for probably 30 sec before I got to the side of the road and shut it down.
Anyone had any experience with this? How bad is it? And most of all, why would you put a huge knob on the outside of the head for a noob like me to be tempted to fiddle with? ARRGH!
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