Clearly the engine is dragging the throttle linkage down to lower the idle. I'm far from an engine expert but given the age and mileage on your bike, I can only imagine it sat idle the majority of the time. That suggests to me that there is a problem somewhere in the throttle linkage. It also fits with my theory that the lubrication, either in the cable/housing and/or linkage itself, is gummed up and sticking.I recently purchased an '06 Vee from a guy near Las Vegas (7,200 miles when I bought it, 4 weeks ago, 10,200 + miles now) and ever since I've been riding it, it's had an idling problem.
When I clutch to begin braking, the engine speed usually (85% of the time) rests at about 2200 rpms. If I let out the clutch (and therefore engine brake) to bring the rpms down to 2000 or below and then clutch back in and apply the brakes to continue stopping, the bike will idle back where it should, around 1100 - 1200 rpms.
The high idle occurs whether or not I engine brake almost exclusively (but still keep the engine speed above 2200 rpms until I clutch in fully and then complete the stop with the brakes) or don't engine brake at all and just use the hydraulic brakes.
Probably unrelated, but worth mentioning - the bike will also missfire occasionally (probably once every mile or so) when cruising in 2nd or 3rd gears going around town, 25-35mph.
As you decelerate using engine braking, the engine creates a vacuum that pulls the linkage shut.
That's my theory. It's probably worth what you paid for it.:green_lol:
BTW, I am a firm believer that operating the engine around town at RPMs below 4k will tend to cause performance problems. Specifically, clutch noise and misfiring. I'm not talking about neutral throttle situations or decelerating, but rather rolling on the throttle with anything other a gentle touch. The bike is amply geared and energetic at higher RPMs to permit a down shift for those raucous moments when you want to enjoy more explosive acceleration. Just my $.02.