One tricky gear.

[clyde]

OK so got a Genesis CdF.
All gears change and index fine but.... Hear goes. When I'm in top gear (small cog) it every know and again tries to jump up a cog. No rhyme or reason. Very annoying when you are giving it the beans.
Help.
I'm pretty good at mechanics but this is doing my head in. Don't want to start messing unnecessary and have to re set the whole gear system if it's something easy I've overlooked.
Give me an old 10 speed any day. 😂

 

[I like Skol]

Sounds like the stop screw might want turning out a bit?

 

[ColinJ]

And/or friction in the gear cable?

 

[Erasmus]

I had a similar problem which was cured by just tightening in the B tension screw to give a tad more breathing space in this gear. Not sure why it was ok sometimes and not others, but this worked for me. Good luck, John.

 

[Gunk]

It could be that the cable is a bit too tight, try turning the barrel adjuster clockwise to release the tension slightly