Engine Seized? Help!

So I bought a '78 KZ400. I've been tinkering with it trying to get it to run right. I had the carbs professionally cleaned, got new sparkplugs and sparkplug wires, and a lot of other little parts.
The biggest problem was that just one cylinder was firing somethimes and it would alternate sides. But today, I got it to run on both after messing with the air/fuel ratio.
So while it was running, all of the sudden "CLUNK" bike makes a bad noise and just shuts off. Tried to crank it over (I only have kickstart) and the kickstarter was frozen and wouldn't turn over. My friend and I tried a few things, thought about it and decided to just taking apart the engine. Didn't find anything, but when we decided to turn the engine over with a wrench, it turned over! So what is wrong?! The kickstarter bearings? Does that make any sense? Before you ask, yes there was plenty of oil in it.

Any help/guidance would be appreciated!

Here's a sparknote version for those who don't want to read my story;
-Bike running on one cylinder radomly.
-New plugs/wires.
-Kinda fixed.
-Ran on both cylinders.
-Clunk. Bad noise.
-Kickstarter stuck, won't turn the engine over.
-Engine will turn over via the bolt with a wrench.
-Top end of engine is now dismantled.
-HUH?! Help?!

Here's a pic just cause I know there will be at least one of you asking for one

you can turn the engine at the crank, but can't with the kick starter... will it turn over of you push the bike in gear? if not the problem is in the transmission then. take the oil pan off and have a look.

Tyler wrote: you can turn the engine at the crank, but can't with the kick starter... will it turn over of you push the bike in gear? if not the problem is in the transmission then. take the oil pan off and have a look.

Yes, sorry, I forgot to mention that while on the centerstand, we rotated the wheel and it turned over in gear. I also haven't even taken this thing for a ride yet. Whenever I've started it and kept it running, it always has remained in neutral. The gears feel solid when I go through them while the bike is off.

kickstarter assy or starter clutch?

bountyhunter wrote: kickstarter assy or starter clutch?

I mean, that's what I'm hoping for I guess....

Hi Brat and welcome aboard (a crazy ride).

I'm actually in the same boat after buying a second '79 KZ650. The bike was a sweet deal for me since it came with a Kerker exhaust and electronic ignition - however, the PO sold it to me for cheap because a 300 lbs guy couldn't get it to turn over at the kickstand. It's been a couple weeks since I got the bike and haven't started looking at it close enough. My guess is the kick-starter assembly is toast.

With limited days of riding, I'm saving it for a winter project or parts sale. My advice is to get a Kaw Factory Service Manual and Parts Manual. Start with the starter, kick-starter assembly and then transmission. These good old bikes are great to wrench and learn about how they work. Parts are available from the factory and everywhere on ebay and on this incredible forum.

Enjoy the wrenching because it makes riding the bike so much more enjoyable (... my 79 cents).

Welcome to the forum. where did you get the bike? Where are you at? It looks just like a bike i saw on Craigslist.

soldierbp wrote: Welcome to the forum. where did you get the bike? Where are you at? It looks just like a bike i saw on Craigslist.

Thanks, I'm in the Bay Area

LineArtist wrote: Hi Brat and welcome aboard (a crazy ride).

I'm actually in the same boat after buying a second '79 KZ650. The bike was a sweet deal for me since it came with a Kerker exhaust and electronic ignition - however, the PO sold it to me for cheap because a 300 lbs guy couldn't get it to turn over at the kickstand. It's been a couple weeks since I got the bike and haven't started looking at it close enough. My guess is the kick-starter assembly is toast.

With limited days of riding, I'm saving it for a winter project or parts sale. My advice is to get a Kaw Factory Service Manual and Parts Manual. Start with the starter, kick-starter assembly and then transmission. These good old bikes are great to wrench and learn about how they work. Parts are available from the factory and everywhere on ebay and on this incredible forum.

Enjoy the wrenching because it makes riding the bike so much more enjoyable (... my 79 cents).

Thanks, that's solid advice. I already stripped the bike down so I will know soon enough what happened. Good luck on your bike as well!

It's been a while since I posted anything about this problem. I've been busy with work and school but I'm getting back to the bike now.
I cracked the cases open and found that the engine is actually really clean and in good shape and the kick start assembly looks and works well now, which is really frustrating. I don't want to put the engine back together without fixing something...

I have a couple questions for you guys before I move on.
- Should I just replace the kickstart assembly anyway?
- I was thinking about just buying another engine. Is the KZ 440 a better engine and does it just line up and mount the same as the 400?

Don't bother with the switch. The kick start is meant for emergencies, not for every day use. Mine has lasted for 40 years that way. A lot of guys don't want to buy a battery but don't know the bike depends on it for everything. Look closely at the shift drum, shifting forks and the shift lever inside. My question would have been, does it turn over with the clutch pulled in and the starter is being used? Now you have it open, that doesn't apply. Pics?
Steve

I believe A LOT (if not all) kz400s dont have an electric start.