Gremlin in the rear end
I just purchased a 2004 GT with 29,000 miles a little over a week ago. The tires on it were trash, so I did not do much of a test ride- did hear something in the rear end that seemed 'off', but still felt it was a good enough deal to buy. So I did.
My first thought was final drive bearing- got it home, drained the final drive to look at the fluid- it was very clear. Too clear.... I wondered if metal had been flushed by the previous owner. So, I put fresh fluid in, and drove around a bit. There is something going on. Wish I could describe it well- strong vibration in both foot pegs, and intermittent sound of something rattling in the rear end. At times, the bike is smooth, and then hit a bump, and it carries on for a while. There is a bit of a 'jerk' at very slow speed when I grab the brakes- as though something is moving- I just don't know what.
With about 100 miles on it, I parked it, and started taking it apart- drained the final drive fluid again- very clear, no signs of any metal or pieces. Rotates smoothly, no crunch or unevenness. No oil on wheel or around seal. I did feel a small amount of lateral movement at the pivot bearings, and really thought that would be the issue.
I will point out that the driveshaft looked factory fresh- had some lube on it, but not much. No oil in the swing arm at all. Very, very clean. I could not detect any movement in the swing arm laterally, vertically seemed very smooth.
I replaced the pivot bearings with the Rubber Chicken Garage Bushings, and thought that would take care of it. It didn't. Absolutely no difference whatsoever. I was very disappointed. So, parked again, took the wheel off, thinking maybe I didn't torque the bushings enough. However, still very solid.
The only other abnormal item is the shock- it's an Ohlins, and I have the receipt for a rebuild about 900 miles ago. I played with settings, and when I made it as stiff as possible, there 'might' have been some improvement. I might have imagined it, as well. The connection on the swing arm is rough, though. As though the shock doesn't fit properly, and has worn away some material at the swing arm. The bushing isn't in great shape, but it's not awful. I marked around the mounting point, and took it for a ride, thinking that if there were movement there, the marks would rub off. No indication of movement.
So, I'm at a loss. With the amount of noise, I would think that if it were the final drive bearing, there would be more evidence. I cannot imagine what I'm experiencing is normal for this bike. When I was at speed, there felt like a small amount of drift in the rear end. It did not feel stable.
Any advice? Does anyone think it could be the final drive bearing, despite no evidence? I just don't know where to look at this point. Any suggestions would be appreciated. Thanks.