HELP! THIS CLUTCH HAS GONE MAD!!

Hi, all! This is my first post on the forum (so don't chew me up too bad ). I'm having some difficulty with the clutch. First, a little intro about the bike.

I first bought this 1976 KZ400D 3 years ago from a used motorcycle parts warehouse, with open title. I later found the original owner (who still lived in the area! small world!), and he graciously wrote me a bill of sale, so all legit at the DMV. I have since ripped apart the bike and rebuilt everything, apart from inside the engine itself. I also did some custom work, chopping, welding, and painting the frame, restoring, filling, and painting the gas tanks, new muffler, heat wraps, mikuni carburetors, wiring harness, chopped fenders, custom seat I built, rebuilt front and rear brakes, rebuilt forks with new seals, respoked rims, new tires, new signal lights, hand painted side covers, the works. She is now a beautiful brat/cafe style bike (see attached photo).




Among the technical issues I have run into, one of the biggest were the keihin carbs. Although I had started the bike up with the keihins before, I bought two rebuild kits and rebuilt them five or so times before deciding to buy a pair of mikuni MK30 carburetors, which came with these puffy pod filters and 2-in-1 throttle cables. After slapping them on, the bike started after only a few kicks. Luckily, it was on it's center stand, and here's where we come to the problem. Before attaching the new carburetors, I had to take the engine out and send it to a machinist to fix some stripped plugs/mounting holes which were just too far gone for me to re-tap myself. After getting the engine back, installing, hooking up electronics, new carburetors, and chain, I noticed that when I turned on the bike, the neutral light wasn't coming on. I found this odd as when on the center stand, I could feel the clutch was in neutral when I kicked the shifter half a click up from 1st, the wheel spun freely. Also before remounting the engine the neutral light and gear shifting worked fine. I tried starting the bike up, and lo and behold, only a few kicks with the choke (it was around 25 F outside) and she started up. However, the rear wheel immediately started spinning, fast. I tried pulling in the clutch lever, but the wheel kept spinning. After fiddling for a bit, I shifted half a click up from 1st, felt that it was in neutral, but the light still wasn't coming on, and the wheel was still spinning. I tried to stop the rear wheel by hand and it did. When I shifted down into first, even with the clutch lever pulled in, the gears would not disengage and the wheel kept spinning. Stopping it by hand was a no go, though the rear brake DID stop it. Additionally, when I pulled in the clutch lever and kicked the kick-starter, the shaft moved completely smoothly with no resistance or feeling of compression, which leads me to believe that that part of the clutch disengages properly. What the hell is going on? Has anyone run into this problem before? Before anyone suggests something involving the plates or springs, I drained the oil out and took off the clutch cover, and disassembled the whole clutch assembly. I checked the spring sizes with calipers, as well as inspected the plates for wear or damage, and both were in very fine condition. I should note that the bike is a '76, but the registration tag from the DMV on the forks says 1981, and the guy who it belonged to didn't even remember owning it (fun time explaining that one), plus there was only 5,400 miles on the display. My conjecture from this and the fact that apart from some flash rust and worn seals the bike was in very fine condition overall (basically no wear on rubbers in rear brake hub and perfect compression in both cylinders) is that the bike was very lightly ridden for a few years, then sat in a barn for about 30 years.

Did you do a basic clutch release adjustment? and following the procedure in the owner's manual or Kawasaki FSM?

I've adjusted the clutch following the owner's manual procedure many times.

The problem is when I shift down into 1st, the wheel automatically starts turning, even if I have the clutch pulled in, so I'm worried that if I try doing this with the rear wheel on the ground, the bike will just rocket away, as opposed to me easing off the clutch lever and making a smooth transition to movement.

With ignition off and bike in neutral, it kicks over fine, and pulling in the clutch frees up the kicker so the pistons won’t rise ( as it should). However, after selecting first gear, pulling in the clutch no longer disengages the drive train.
I've examined the clutch plates and measured the spring heights on the clutch basket and all checks out. This is a very low mileage machine that sat for a long time. I can’t figure out why the clutch disengages in neutral but not in gear. Even if a selector fork were bent, shouldn’t the clutch disengage?

Just relaying an experience; My brothers 5 speed car (01 Eclipse) while spin the wheels in neutral when on jack stands. If you put it in first and hold in the clutch the wheels continue to spin, but you cant stop them like you can in when it is in neutral. It shifts and drives just fine down the road.

The rear wheel spinning in neutral is normal & you should be able to stop the wheel spinning by hand. I would guess it should spin the same in 1st when the clutch is disengaged (clutch lever pulled in), but I've never checked that.

I would make certain the clutch cable is in good condition (not worn or stretched), installed properly & actuates the clutch release properly. also make sure the clutch release is good. check the diagrams to make sure your clutch release n stuff is correct.

I would then do the clutch adjustment as per the Kawasaki manual. then if necessary, turn the release screw a little more in or out as a fine adjustment. On some models you have to turn the clutch release adj screw counterclockwise first.

ps: when you kick start the motorcycle, you're turning the crankshaft manually to start the engine, so the pistons still move. pulling in the clutch lever disengages the rear wheel from the transmission so that the crankshaft turns easier.

What Martin said....rear wheel spinning on the center stand while in neutral is normal but with not enough authority to move the bike if it were on the ground.

Curious what type of engine oil are you using. I've had an experience using an oil (which shall remain nameless to protect the innocent) which was too vicious and would not allow the clutch plates to disengage until the engine was all the way warmed up. Even then I had to break the plates loose by pushing the bike while pulling the clutch lever.