Return spring on Z1 gear shift

I noticed there is little or no return spring action on my gear shift lever.  It will move the gears and I can put it in and out of N, 1st and 2nd.  Anyone know what all needs to be done to fix this?

My money is on a shift shaft that is gummed up with old chain lube and dirt, or a worn out shifter return spring. Maybe both.

Or a bent shift shaft ...
 

wrote:

My money is on a shift shaft that is gummed up with old chain lube and dirt, or a worn out shifter return spring. Maybe both.

Good guess TexasKZ.  Was glad to see the shifter drum is accessed from the left side.  Just had to remove the front sprocket and the cover behind it.  Everything looked normal.  I put the shift lever back on and spring action was perfect.  So I'm cleaning everything really good, lubing the seals and putting it back together. 
 

Ugh!  Put it back together and while it's better, it's still not right.  Looks like there's a bit of wobble in the shaft.  How big a deal is changing that?  With the side cover off, return spring feels strong and it shifts fine, when it's back on shifter is very slow to return to center.  Anyone know what is the one shaft that's it's important not to pull out or somethings falls off on the engine side and the case will need to be split?  Looks like the shaft the shifter attaches to just rides in a bearing or boss on the engine side.

Spread the shift mechanism arm enough to clear the shift drum and it pulls straight out. Check that numbers 11, 12, and 13 are in place and in good shape. Clean all shaft seals of old grease.especially between the two seal in the counter sprocket cover. Regrease the lips of the seals and reassemble  

Thanks Mikaw. I did what you said.  Must have had the outer and inner covers off ten times.  Last time I pulled the shifter rod and cleaned and polished it.  After I put the inner and outer covers on it's much better than it was but still feels a little week.  Spring brings it back down or up but doesn't quite hit center some times.  Checking it against my KZ900 it's night and day.  The KZ has a strong spring response to any movement. Could probably get by with it the way it is but since I've got it all apart I may as well order a new spring. Thing is, without inner and outer covers and the drag from the two seals, it works perfectly. Gotta be the spring, unless the rod is bent.  I put a straight edge on it and it appears to be straight... but really hard to tell with 6 inch straight edge on a 4 inch rod. Those seals are providing just enough drag to keep the spring from fully doing its job.

The spring develops a crack making it weak. Suggest a KZ 1000 spring. They have one more wind making it stronger. The seals act as a bearing for the shaft. There are three of them. If the shaft is sloppy it can cause miss shifts so I'd order them as well.
Steve