Jumping out of 4th gear

Hi everyone, Sorry for my first post being a request for help but I am unfamiliar with British bikes and have been unable to find an answer to my problem using searches.

I have recently purchased my first classic bike a MK11A 850. I am very pleased with it but it does have one problem at the moment. I can go blasting around the country lanes without problem up and down the box. Both on acceleration and deceleration it will hold all the gears.
However when I am cruising on the dual carriageway in 4th at about 70/75mph it will jump out of 4th and mainly go into 3rd but occasionally go into a false neutral.

Is something likely to be worn and the vibrations making the gears change? Or is there something I need to adjust somewhere.

Thanks in advance, Steve

That would suggest worn bushings in the box. I would suggest going through the gearbox internals and refreshing as needed. Jim

Thanks for the prompt reply Jim,

Looks like a full box stripdown then Was hoping it was going to be a quick fix that was needed as I am loving riding around on it. Massive grin everytime I go out.

Cheers, Steve

Steve

You might consider replacing the cam-plunger spring--sometimes the fourth-gear notch on the camplate is a little shallower than it should be.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos

Thanks Tim, I willl try that first.
Steve

+ 1 with Jim and Tim. In adddition, I would strip down (Norton gearboxes are easy) and MAKE DARN SURE your layshaft bearing is the upgraded "superblend" bearing (FAG NJ203 C3) ... otherwise you can be in for alot of grief. You have been warned ...