Ok, so about three years ago, maybe four, about this time of year I replaced my front and rear sprocket and the chain on my Hayabusa motorcycle.
I’ve replaced the chain several times and change sprockets every other chain change.
Probably after the trip to Alaska I frond the bike was surging a bit in 4th gear. This is sort of a lower speed cruising gear. It would sometimes be pretty distinct but at other times it’d be barely noticeable. Still there but very minor.
I tried several things to identify it but nothing was clear when going over the bike during oil changes or other maintenance. It wasn’t the engine. I didn’t see the tach needle move when it was surging. That left transmission or drive train.
Two years ago I chatted with the local bike shop while they were changing tires. The mechanic suggested, after a test ride, that the cush drive might have gone soft. As they’re individual pieces, one being softer would give a surging feel.
On the bike, the sprocket is mounted on a floating hub. This interfaces with the wheel via six slightly V shaped pieces of rubber. It gives a little so acceleration and deceleration aren’t so abrupt.
Changing them out was an adventure in itself necessitating a phone call to the guys who created them because I couldn’t get the hub back on the wheel it was so tight. I had to jump on it to get it seated.
So this past fall, I bought a chain and front and rear sprocket planning on replacing all three. I removed the left side plastic, removed the seat, removed the overflow and speedometer, and finally the cover to the front sprocket.
What did I find outside of grease and grime?
The front sprocket was loose! I could move it about a sixteenth of an inch. That would explain the odd behavior.
I put a stick in the wheel spokes to hold the wheel in place and removed the speedometer bolt then the drive shaft bolt.
In examining it, there is the sprocket, a washer that fits on the shaft, a 33mm nut and a second washer/speedo bit that is held down by the speedometer bolt.
It turns out the washer dropped off of the shaft to lodge between the collar and the nut leaving a little room to move.
I ensured the washer was in place after mounting the new sprocket, tightened the nut to spec, made sure the sprocket didn’t move when done, put the speedo back together and reassembled the left side of the bike.
I also pulled the hub and replaced the sprocket with a new one. I was going to replace the chain but my chain breaker was broken so I cleaned it and tightened down the bolt to spec.
I took the bike out for a ride and the problem was fixed. 🙂