Happened a few weeks ago but only just got around to posting. Everything working ok and then gearlever went all loose, stopped and checked linkage which was fine, was obviously an internal problem so managed to ride home 30 miles in 3rd year. Had to change the pivot plate last year so had experience getting to the gearchange mechanism, found a pin broken off the gearchange shaft which acts on the big spring that returns the shift lever back to centre. Pulled the shaft out hoping the pin could be replaced but it's not removable, at a push could have tried to get it tig welded somewhere but not sure I'd trust it. Also had some wear on the bearing surface at the lever end so purchased a new one from Fowler's. While I had it apart found some wear already on the shift plate even though it was only replaced about 4000 miles ago. For the sake of twenty odd quid I replaced the shift plate again, this is obviously too soft as there is no wear at all on the detent wheel. Used the original spring on the shift plate as it was also replaced last year but fitted an extra washer to keep a bit more pressure on the plate, may help, might not. Went back together ok , managed to re-use the gasket, no need to drain the oil, gearshift feels better than ever now, really positive with the new plate and zero play on the shaft. Measured the clutch friction plates while they were out and they are only 20% worn, so not bad for 22,000miles Hope this is useful to others to diagnose shift issues, when the shift plate wears excessively the bike will not shift either down or up, in my case last year it would shift up but not down, didn't happen gradually either. Obviously this time with the pin breaking everything was fine up to that point, when you see the size of the pin first hand and the strength of the spring I'm surprised it lasted so long given it presses against the spring every up and down shift, God knows how many shifts in 22,000 miles
I have just repaired a new 1200 bonneville. That shift plate had broken. A piece came off and fell into the oil pump chain which snapped. That's why the bike was cat N. So think they could be a bit of an Achilles heel.
