Why can't I change gear?

Q. I have a 1979 Kawasaki KZ400 that I use for travelling between college and home; it’s in very good condition and has only done 4500 miles.

The problem is that shifting into second gear is very difficult. It shifts down gears fine, and shifts up fine on every gear apart from second. To get the bike into second I have to literally kick the shifter up with extreme force.

It’s particularly a nightmare when pulling away from lights, as cars must wonder what the heck is happening when they see me travelling at 15mph for one minute while I desperately try to get the bike past first gear.
Tenacioustim, MCN forums
 
A. If you have checked the clutch action and gearlever position it could be internal. Kawasakis from that era are fitted with a positive neutral finder that uses a couple of ball bearings on the gearshaft.

If the balls get stuck they won’t allow you to change up as the bike thinks it’s still in neutral. The first thing to do is to put some fresh oil in and get it properly warmed up with a good thrash which will hopefully move the crud holding them in place.

If that doesn’t work it could be a gearbox strip.