Help me figure out my startup knocking / clanking

There are a few startup knocking / clanking threads but none of them sound quite like mine.
1982 KZ 440 LTD Belt Drive

When I start up cold, I need full choke for about a minute (~5k RPM), then half choke for another minute or so (~2k to 3k RPM), then it will idle without shutting off.

While on full choke / first minute, it makes some weir noises:
- Periodic clanking, like a "clack... clack clack... clack..."
- There is also a sort of knock that happens that is difficult to describe. Infrequent and usually has a slight dip in RPM after.
- The right side exhaust is somewhat irregular and makes a popping noise, almost like a crackle. Similar to a back fire but less loud and more sporadic.

During the second minute, if I do not use half choke, it will struggle to keep going. If I put in a little bit of throttle and get it up to ~2k RPM, it will struggle and have frequent dips in RPM / often shut off.

After about 2 minutes of this fairly rough warm up, it gets a little better. And after about 4 minutes in the thing runs and sounds just fine.

I took some videos of it this morning and will upload them to youtube later.

Any help, ideas, suggestions etc. would be great!

Is all the bikes maintenance up to date? Valve adjustment, clean carbs with fresh O-rings, fresh spark plugs and coil wires/caps in good shape, petcock working properly, fuel level in the carbs checked and adjusted as needed, etc? Also, is the bike all stock or modified?

Loose starter clutch?

Looks/sounds like there’s a sprocket slipping on a chain.

Maybe sync the carbs and adj the cam chain after Nessium's advice ?

I purchased the bike from the 2nd owner and it had under 10k miles. I would assume that the 10k tuneup was never done, so it may just be in need of regular maintenance?

I think the clanking does sound somewhat similar to the starter clutch chain slipping. But it is not as frequent as that video.

I uploaded videos to youtube (below):

Sounds like it's just running poorly. Clean the carbs and do all the various maintenance tasks and consider replacing the carb boots while you're at it. Don't waste money on "carb kits" just clean the jets you have and replace soft parts like O-rings.

Wow. I couldn't bear to watch the whole video. Why would you let the engine sit there and idle at that high rpm? Ed

Hi Ed,

I keep it at full choke on startup to help warm it up. I have never heard of that being an issue... the video maybe makes it sound bad but it is running at about 5k RPM; it's nowhere near the red zone. Is there something about this that can damage the motorcycle?

It sounds like a carb cleaning may be in my future. I have not done one before but will give it a shot.

Thanks!

On my KZ650C1 I use the choke to start the engine when cold, but I turn the choke part way down long before it revs up high. I generally let the engine warm up with the revs at about 1200 - 1500rpm. Letting a cold engine rev up high strikes me as a bad idea since the oil hasn't warmed up and circulated through critical engine parts, so lubrication may be minimal. Not only that, even with the engine warm I don't let it rev up very high in neutral. When riding I don't mind taking it up to redline, but revving an engine that has no load on it seems abusive to me. One other thing to consider is the fact that when an engine is cold the pistons and other parts have not expanded to their normal running dimensions, so in my opinion revving a cold engine to high rpm isn't a good idea. Ed

I don't think letting the engine run at 5k on choke will hurt anything but it's unnecessary. I'd scale back the choke to about 3k and lower it further as soon as the engine will accept the reduction.

Be sure to pick up a copy of the real Kawasaki manual for your bike and then catch up all the maintenance tasks. It's important to do things like valve adjustment and brake system flush, or clean out if the fluid is brown, in order to avoid problems in the future.

Good luck

Here's a quick way to warm up a Kawasaki. :woohoo: Ed