Kz750 twin won't shift into 3rd

Hi, after a lengthy rebuild I finally got my bike oout for my first test ride.
I can comfortably sift from 1st to second ok but can't shift up any further. Runs nice and clutch feels good.
When I rebuilt the engine I didn't change anything in the gearbox part from cleaning and visually inspecting for any wear etc.
It all seemed ok so was re assembled as original.
Is there any thing to check or test before I take the sump off and check the gear / selector assembly. Very frustrating after thinking every thing was good when assembled.
Any help would be appreciated.

It could be a shift fork. The factory manual has some good info on the tranny. You'll need a manual if you don't already have one.

Bad shift selector spring behind the tranny cover?
Steve

Thanks Bounty hunter. I've read through the service manual which as you say has a lot of info. I couldn't see any thing obviously damaged or bent etc when I reassembled it.

Thanks swest , do you know if there's any way to tedt changing through all the gears with the side cover off.

There are two springs under there. One big one on the lever shaft and the other on the shift ratchet. You can tell if they're broken. Also the shift drum pins might have a problem. There's a small spring on the detent arm too. It's the cover behind the sprocket.
Steve

Hey thanks guys, after checking I found I had installed the shift return Spring incorrectly. Now going changing through all gears with no problems.
Another big step toward completion. Getting close now , can't wait to get on the road. After the test ride I found a small oil leak at front of head. Maybe need to re torque head nuts?
Blood , Sweat and Beers!

Pic of bike before road test.

Cool.
Steve

The head should be retorqued after the very first heat cycle after reassembly, and again after the first 500 miles.