Malfunctioning positive neutral finder?

Hey guys- I recently picked up a 76' kz400 with under 4k miles. The bike runs great, but when I took her out for a ride she wouldn't shift up into second. I'm aware of the positive neutral finder as i've owned a couple older kawi's. One time when it did end up shifting into second, it made a terrible, ear splitting grinding and I quickly down shifted . What the hell could this be? First gear feels fine, clutch tension is fine.

Any help is appreciated, Cheers

Take a look on the shift drum mechanism parts. Opposite to the big KZ´s the mechanism is located behind the clutch basket (right Hand engine cover).

In addition to what Scirocco posted the Kawasaki service manual will have a troubleshooting section that outlines some of the possibilities. The KZ400.com site has a pdf manual. Warning: the forums there may harm your computer.

As mentioned above, it could be a bent or broken part in the shifter mechanism, or a bent or broken shift fork, or the second gear engagement dogs could be badly damaged. There is also a chance that there is a foreign object floating around insid the transmission. A bolt, or a washer, or some such.

Did you try to engage third gear?

If the external parts seem ok, then it may be time to remove the oil pan and peek inside.

TexasKZ wrote: As mentioned above, it could be a bent or broken part in the shifter mechanism, or a bent or broken shift fork, or the second gear engagement dogs could be badly damaged. There is also a chance that there is a foreign object floating around insid the transmission. A bolt, or a washer, or some such.

Did you try to engage third gear?

If the external parts seem ok, then it may be time to remove the oil pan and peek inside.

I took it out yesterday, if I really pushed the bike to say 5-6k rpm in first, it would shift into second sometimes, but then slip down into neutral after I applied any power while in second gear. Once in third, the bike felt great.

I would bet on buggered engagement dogs on second gear. If that is the case, I suspect the most likely solution will be to buy a used set of transmission gears and hope they are better.
So far as I know, the only way to know for certain is to open up the tranny and begin very careful inspection and measurements. You will need the factory service manual and some good measuring tools. Don't be bashful about asking questions here. This can be a daunting task to somebody with limited experience, but there are helpful members here with lots of experience and help to offer.

I'd check the shift return spring first.
Steve

Yes, definitely check the shifter mechanism before diving into the bowels of the thing.

I'll look into the return springs and the whole ratchet assembly this weekend. Thanks a lot for the help guys i'm hoping I don't have to split the cases. Never had a bottom end apart before.