Help! Sudden Transmission Rattle

[Xdot]

Well, I replaced my handlebar the other day with something a bit less aggressive. It's a tedious job with the heated grips but seemed to go without a hitch. I fired the bike back up and it seemed to run fine in neutral. However, when I pulled the clutch lever in I got a bad rattle from the transmission area No hint at all when in neutral and running, but the instant I pull in the clutch handle I get a rattle. It doesn't seem to have the symptoms of a spline failure. Especially since it doesn't make any noise at all in neutral. Only with the clutch pulled in. The noise seems to come from the rear of the transmission more than from the front but it is hard to tell. Thought it might be air in the clutch hydraulic line since the master cylinder got inverted during the swap. So, I bled the system as best I could. Didn't help. Transmission fluid seems topped up and in good condition. I don't have any fear or hesitancy about pulling things apart as deep as necessary but I don't know where to start.

Bike is an '04 Rockster with 15K. Acquired by me in late October. I have put maybe a thousand miles on it since then as weather has allowed. The bike had sat for a few weeks and temps dipped into the low single digits for a couple of days. Shouldn't matter but that was the only thing that happened between parking it and starting it, other than the handle bar swap which meant removing the tank, etc...

[CycleRob]

Xdot,
That sound is directly linked to a failed throwout bearing, which happens to be quite small considering it is a sealed bearing under a constant side load when you are riding down the road. Looking at the heavy return spring tensioned BMW design, I am surprised it lasts more than 20K miles. Your bike's very low mileage is less relevant than the hidden corrosion caused by the last 13 winters, very dark, water contaminated DOT3 fluid leakage past the piston seal -or- a very clean bike that was washed often.

Remove and take the clutch slave apart and do it now! You'll likely find a very ground up ball bearing assembly, a slave piston that has been spinning in its' bore, requiring the slave assembly be replaced. You may also need a replacement clutch pushrod, if either ball end is worn away too much.

[Xdot]

Certainly makes sense. I felt it must be in the slave cylinder. I guess that's what you're referring to. I supposed the standard procedure is to order a new one. I was watching one of those BMW service videos with the guy who swears a lot. Says the BeemerBoneyard slave cylinder is the way to go. And it's about half the price of OEM.

The fluid wasn't in bad shape. A little cloudy but I've seen much, much worse. But the bike was incredibly clean, so perhaps the latter. Wonder if the extreme cold, and it was in the teens or lower for over a week, could have crystalized the water in the brake fluid and pushed the parts in the slave cylinder out of spec.

[sykospain]

Whilst waiting on the arrival of Boneyard's better-spec slave cylinder, Xdot, you can always do the easy starter-motor-removal check to see if there's also any of the dreaded spline wear.

When doing this check, there's no need to strip the bike down or remove the tank:- thirteen bolts, four fuel lines and an electrical connector - now who thought that routine was sensible, practical or necessary in order to gain access to the f***ing battery ? ? -
- although most people do recommend unhooking the neg cable when doing any electrical-system maintenance. Horses for courses...

When removing the starter, there's actually no need to disconnect the electrical cables to it. Just observe where the subsidiary cables go behind the motor for when you refit it. They're the neutral-indicator wire and the side-stand-safety wire; both held to it with a zip tie. Remember where they were and don't trap those thin cables in the bell-housing as you re-attach the starter. And don't scrape the skin off your forehead when struggling to get at the starter's almost-inaccessible lower fixing bolt - sufferin' succotash...

Here's middle-son Tim doing the check :-

https://vimeo.com/253821967

AL in s.e. Spain

[EasyBee]

Simple trick to remember where and how those cables connect : take a picture.